Main classification of PAC 49

MAIN CLASSIFICATION OF PAC

INTRODUCTION

Von Gräfe (1859, see Barkan9) was the first to distinguish between “chronic” and “acute congestive” glaucoma (the latter group undoubtedly contained a mixture of both acute PAC and “haemorrhagic”/ ”inflammatory” conditions). Following Otto Barkan’s9 systematization of gonioscopy in 1938, it became possible to objectively classify the various glaucoma conditions that exist. He proposed a gonioscopically based classification of open and closed-angle glaucoma. At the same time, he recognised the mechanism in pupil block and the influence of the iridectomy on this. This was not, however, generally accepted until the 1950s. The work of Barkan was to a high degree inspired by the studies of the Swedish ophthalmologist Bengt Rosengren (1930-1931) concerning the relationship between the axial chamber depth and acute glaucoma.

However, angle-closure due to plateau iris was not described until 1958 by Rosengren’s colleague Ragnar Tørnquist12, and it is only in the last decade that this form of PAC has generally become accepted as representing an important clinical entity. Therefore, no clear diagnostic criteria for this condition can be found in the glaucoma literature.

Finally, it should be noted that it is only in recent years that there has been a wider interest in the detection, thorough clinical classification and specific treatment of PAC cases.

There are several possible explanations for this:

1.Until 1978 when beta-blocker agents first became available world-wide, the drug treatment of open angle glaucoma and PAC were identical, i.e. pilocarpine drops. Moreover, acute glaucoma presented itself with an acute onset. As the frequent occurrence of asymptomatic “creeping” angle closure was not fully documented, the need for detection and classification with a view to specific treatment was mostly purely academic. Today, as the number of “non-miotic” glaucoma eye drops is so manifold that the use of pilocarpine can generally be avoided, the need for

50 Main classification of PAC

adequate classification prior to starting treatment has become essential.

2.With the documentation of the usefulness of LCD assessment as a PAC detection method in 198831 and following the development of YAG-laser iridotomy in 198413 and argon-laser iridoplasty in 197914, a basis both for the detection of and for the uncomplicated preventive treatment of PAC was laid.

3.As mentioned in the introduction new population studies show that the world-wide visual disability from PAC is proportionally greater that from POAG due to the high prevalence of PAC glaucoma in Asians and Indians30, 40.

The description primarily connected with angle-closure refers to the congenital pathoanatomical risk factors mentioned below and can be regarded as the opposite of the acquired risk factors in the secondary types of angle-closure (inflammatory and rubeosis conditioned PAS, lens luxation, ciliary block, etc.).

Therefore, we define primary angle-closure (PAC) as a condition with either imminent or manifest angle-closure due to congenital, specific pathoanatomical conditions.

As accounted for in the introduction, the use of the term glaucoma will be confined to conditions where there is either a permanently increased eye pressure due to peripheral anterior synechiae (latent glaucoma) or where this is combined with classical structural and/or functional glaucoma defects (manifest glaucoma).

MAIN CLASSIFICATION AND METHODS OF CLASSIFICATION

As appears from fig. 18, PAC can be classified by means of gonioscopy and axial chamber depth measurement (ACD) into 3 main groups:

Group I. PAC with pupil block

Group II. PAC with plateau iris

Group III. PAC mixed group (I+II)

Main classification of PAC 51

Gonioscopy is not only the necessary diagnostic tool as far as PAC is concerned; it is also important in the classification of PAC, as gonioscopic assessment of both iris contour and mobility with the Posner lens (ref: Gonioscopy, 1. Iris contour and iris mobility, p. 33) constitutes the basic means of differentiating between the three main groups. The above-mentioned main classification may, though, be difficult to perform adequately without the simultaneous use of ACD measurement. As stated in the chapter concerning axial chamber depth (p. 11), ACD assessment is not only of diagnostic importance in connection with the pupil block conditioned PAC form, but is also a necessary supplement in order to distinguish the three clinical PAC main groups with regard to their specific treatment.

The above-mentioned application of two combined methods of examination (gonioscopy and ACD: combined risk-factors) for diagnosis and classification of early PAC in order to achieve adequate indications for specific treatment corresponds exactly to the recommendations in connection with open-angle glaucoma (Danish Glaucoma Society, 199721: Combined risk-factors as diagnostic criteria for latent POAG).

Fig. 18. Main classification of PAC.

The specific treatment within the three main groups varies with the stage of PAC development, and the three main groups are therefore subdivided. Each of the main groups is subclassified in the same 6 PAC stages of development defined by means of identical objective criteriae. The terminology and definition of the individual subgroups therefore are the same in groups I, II and III (Fig.19). On the other hand, the recommendable, specific treatment of each individual subgroup differs in the three main groups. In order to

Main classification of PAC 53

facilitate the use of specific treatment with an expected adequate effect a recommendable procedure therefore is attached to each individual subgroup concerned (Fig.19).

As stated in the introduction of this book, we define specific treatment as a procedure which, guided by the findings from the initial objective examination, is adapted to the observed specific pathoanatomy and PAC development stage of each individual eye.

The main classification, subclassification and specific treatments are illustrated in a schematic flow chart (fig. 19).

It should be noted that the authors have used the described classification procedure in practice throughout several decades25. The classification is alone based on the most typical, objective changes found in each main group and individual subgroup. Therefore it should be emphasized that the purpose of the present book is not an epidemiological description of the various more or less frequently found PAC manifestations based on both subjective symptoms and objective signs.

The use of the combined diagnostic methods (standardised PAC gonioscopy and ACD), the definitions of subclassifications and the attached specific treatments are not specifically to be found in the literature.

←

Fig. 19. Flow chart for specific treatment of primary angle-closure.

Definitions, subclassification:

A:Suspect PAC: Narrow, occludable in the upper sector, not lower, no PAS.

B:Imminent PAC: IOP < 24 mmHg (pressure top), narrow occludable or apposi- tional-closed upper sector and occludable lower sector, no PAS.

C:Acute/subacute PAC: Temporary IOP ≥ 24 mmHg, appositional angle closure involving 360 degrees.

D:Chronic PAC: IOP < 24 mmHg, PAS < 50% of the angle circumference.

E:Latent PAC glaucoma: IOP permanent ≥ 24 mmHg, > 50% PAS < 80-90% of the circumferens, no structural optic nerve/retina changes or visual field defects.

F:Manifest PAC glaucoma: IOP permanent ≥ 24 mmHg, PAS > 80-90%, structural optic nerve/retina changes and/or visual field defects.

54 Main classification of PAC

Main groups and subclassification of PAC 55

MAIN GROUPS AND SUBCLASSIFICATION OF PAC

GROUP I: PAC WITH PUPIL BLOCK

PAC with pupil block is by far the most common form of PAC since this group is believed to make up approx. 90% of the PAC population15. However, it should be emphasized that no accurate population studies concerning these conditions have been carried out.

Pathophysiology and pathogenesis

As already mentioned, in a normal eye part of the iris lies in contact with the anterior surface of the lens. This relative pupil block causes a minimal pressure gradient between the anterior and posterior chambers. This pressure gradient increases throughout life as the lens increases in size. This lens growth increases not only the iris contact area, but also the problematic sphincter iris/ lens contact. The increased pressure gradient affects the thin and elastic iris root more than it affects the central part of the iris. The normal iris surface is therefore typically slightly forward convex in configuration (ref: Normal anatomy of the chamber angle, 1. Iris contour and iris mobility).

In connection with PAC, this normal slight pupil block is increased (fig. 20), leading to a pathological accumulation of aqueous fluid in the posterior chamber with a pronounced frontally convex iris and a narrow chamber angle. The aqueous accumulation explains the extreme iris mobility on indentation gonioscopy (see fig. 14). The therapeutic iridotomy equalizes the abnormal pressure gradient between the posterior and anterior chambers, flattens the iris and opens the chamber angle where possible.

In these eyes, a number of bilateral anatomic features of various degrees are the basis of the abnormal pupil block. These features are more frequently seen in females than in males (F: M – 3:1) and increase with age until around 60-70 years. The eyes are most often hypermetropic with a short axial length and ACD, small cor-

56 Main groups and subclassification of PAC

neal diameter, thick iris root, large ciliary body and, furthermore, with a thick lens. As mentioned above, the lens grows throughout life (decreasing ACD), and since the lens is already attached more anteriorly in the typical PAC eye than in the normal eye, the increasing iris/lens contact may lead to a pathological relative pupil block with age. In twilight conditions, an increased iris convexity due to submaximal pupil dilatation may then lead to appositional angle closure and acute or chronic “creeping” PAC. In connection with maximal pupil dilatation, the relative pupil block is, however, either diminished or even eliminated, whereas it is increased when using strong miotics, especially the irreversible miotic agents such as phospholine iodide. The latter may therefore lead to a so-called paradoxical increase in pressure in PAC cases.

Fig. 20. Imminent PAC with pupil block.

In the rarely found nanophtalmos condition (nanos = dwarfism) the above-mentioned biometric conditions are extremely pronounced, and the risk of PAC development is very high (especially the asymptomatic “Creeping” chronic PAC). Here, the traditional surgical PAC treatment is particularly risky because of post-operative “uveal effusion” and ciliary block. Nanophtalmos is especially to be suspected in very small eyes (axial length: < 20 mm) with thick sclera, small corneal diameter (< 11 mm), hypermetropia of 8D or more and extremely narrow chambers because of the normal lens size in these patients.

However, quite a number of people have some of the described anatomy and yet do not develop PAC17. Therefore unknown trigger factors – psychological or physical – seem to play a part in the

Main groups and subclassification of PAC 57

development of manifest angle closure (e.g. increased blood flow in the ciliary body).

Detection and diagnosis

The method of detection at PAC with pupil block involves the assessment of the limbal chamber depth (LCD). It is recommended that this efficient screening method be used on a routine basis for all new patients in the clinic. In connection with iris/corneal contact in just one single area, a subsequent gonioscopy will almost always verify the PAC diagnosis.

The preliminary gonioscopic diagnosis of the narrow angle is, as previously mentioned, based on the lack of visibility of the pigmented trabecular meshwork under standardised examination conditions (ref: Standardised PAC gonioscopy methodology). In order to be able to perform specific treatment in such a PAC case, it is then necessary to ascertain the presence of any pathological pupil block. As indicated in fig. 18, this is done by diagnosing the pathological frontally-convex iris contour with extreme iris mobility, which results in the opening of the angle on indentation gonioscopy (ref: Iris contour and iris mobility). The gonioscopic pupil block diagnosis can then be verified by measuring the axial chamber depth (ACD). Especially in connection with a difficult gonioscopy (e.g. with a blurred cornea), bilateral ACD measurements are important. In the majority of cases of PAC with pupil block, bilateral ACD measurements of < 2.0 mm will be found (ref: ACD measurement, p. 12). As the degree of narrowness of the goniscopically diagnosed narrow angle cannot be measured directly, it is rational to have a quantitatively indirect measurement for the size of the chamber angle by means of ACD. Moreover, a considerable difference in the ACD value (> 1.0 mm) between the two eyes is of diagnostic importance in differentiating secondary angle-closure (SAC) from PAC.

In almost half of the cases of acute PAC there are prodromal attacks (subacute PAC) with headache, blurring of vision and the characteristic appearance of haloes or rainbows around lights due to brief, mild increases in pressure with slight oedema of the cornea. This is typically caused by mydriasis in a semi-dark environment, followed by pupil contraction when the lighting conditions are increased or accommodation becomes activated (ref: subacute PAC with pupil block).

58 Main groups and subclassification of PAC

However, it is important to underline that most eyes develop asymptomatic “creeping” chronic PAC with PAS without any acute subjective symptoms. This most likely happens to patients with an increased tendency to angle inflammation leading to PAS in relation to appositional closure of the upper angle sector (ref: Glaucoma pathology in the chamber angle, PAS). “Creeping” PAC constitutes 2/3 to 3/5 of all pupil block conditioned PAC cases17, 34, 35. As visual loss due to PAC especially seems to be caused by this asymptomatic form, the importance of early detection is emphasized41.

Cases of latent or manifest PAC glaucoma without prodromal symptom may further be misdiagnosed as representing open-angle glaucoma and thus be incorrectly treated with beta-blocker agents. This form of treatment does not prevent the formation of synechiae and may therefore result in the development of terminal PAC glaucoma. This situation further demonstrates the importance of PAC detection by means of limbal chamber depth assessment (LCD).

Subclassification with specific treatment and case histories

The subclassification of PAC with pupil block and the objective criteria (definitions) for each of the subgroups appear from fig. 21. Further, the recommendable, different specific treatment is attached to each subgroup. This permits the possibility of a satisfactory course of treatment without any unpleasant surprises for either the patient or the doctor.

A

In suspect PAC (suspicio angulo clauso) with pupil block the angle is narrow, occludable in the upper sector, but not the lower one. This is, as mentioned previously, due to the normal angle always being narrowest in the upper sector, i.e. the development of the occludability has not yet spread to the lower angle area. Control without treatment after patient information concerning prodromal glaucoma symptoms is adequate. Control is advisable after 6-12 months with regard to any change on gonioscopy or ACD.

Main groups and subclassification of PAC 59

Fig. 21. Subclassification of Group I: PAC with pupil block and specific treatment.

B

In imminent (threatening) PAC (angulus clausus imminens) with pupil block the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower, but without PAS. The patient can thus in advance be informed that YAG iridotomy (fig. 21) probably will be curative in this situation. This represents the ideal situation as the adequate glaucoma prophylaxis available will result in not only personal psychological advantages, but also practical insurance benefits for the patient. Control is advised the day following laser treatment after 1, 3 and 6 months and thereafter annually.

C

Acute/subacute PAC (angulus clausus acutus/subacutus) with pupil block is conditioned by trabecular meshwork occlusion due

60 Main groups and subclassification of PAC

to appositional angle closure involving 360 degrees. This leads to varying degrees of the classical subjective symptoms due to the acute IOP increase: Blurring of vision with ciliary radiating pain to the forehead and cheek combined with general discomfort with nausea and vomiting. The acute PAC is in almost half of the cases preceded by twilight-conditioned temporary subacute PAC attacks in the form of rainbow coloured haloes around light sources (corneal oedema) with slight blurring of vision and frontal headaches.

Unless the manifest acute PAC attack is treated adequately within the first 24 hours, various degrees of pressure-conditioned ischaemic damage in the form of multiple retinal ischaemic infarcts may arise. In rarer cases, this situation will include varying degrees of optic nerve head lesions. The accompanying multiple retinal microhaemorrhages and dilated veins may be interpreted as representing an initial central vein thrombosis. Long-standing hypertension with associated ischaemia may result in hypotonia due to a reduced aqueous production, and this may give rise to further confusion with regard to the correct diagnosis.

This hypotonia may further lead to false optimism regarding treatment, increasing the risk of overlooking advanced PAC cases with acute pressure worsening. Again, it is necessary to stress the importance of adequate gonioscopy, which should generally be carried out after using 50% glucose drops for clearing the oedematous cornea, as a necessary basis for the specific treatment of these cases.

If the cornea remains cloudy in spite of the 50% glucose drops and it is therefore not possible to establish a definite diagnosis in the affected eye, the PAC diagnosis can always be established by performing limbal and axial chamber depth examinations as well as a gonioscopic evaluation of the patient’s healthy eye. This is due to the fact that the anatomical risk factors are always present bilaterally in PAC even though they are most pronounced in the acutely affected eye3.

Finally, it is good clinical practice to always begin an objective examination with the least discomfort to the patient, i.e. always start with an ACD assessment and a gonioscopy examination in acute PAC in the healthy eye. The examination of the other eye is also essential with regard to determining the indication for preventive iridotomy (remember pre-laser preventive pilocarpine treatment of the healthy eye!).

Main groups and subclassification of PAC 61

Furthermore, a pronounced case of acute PAC will often lead to permanent objective changes in the form of pupil dilatation, sec- tor-shaped grey iris stromal atrophy, anterior subcapsular lens opacity, “glaukomflecken”, and diffuse chamber angle pigmentation, which can support the diagnosis. “Glaukomflecken” are small, white irregular spots in the pupil area situated in the lens capsule or just subcapsularly, whereas the grey iris atrophy, which arises in the weeks following an attack, are seen as greyish areas of iridoschisis in the iris stroma.

In addition, in acute PAC it is recommended that YAG-laser iridotomy be undertaken as soon as it is technically possibletodo- soaftertheinitialmedicalpressure-reducingtreatmenthasbeeneffect uated(ref:TreatmentofacutePAC).This is advised in order to make use of the “synecholysis effect” of the iridotomy before any irreversible, organised PAS have been formed. For the same reason, steroid eye drops are to be recommended with the acute medical treatment of PAC.

Pressure control and gonioscopy should be undertaken the day following laser treatment as well as after 1, 3 and 6 months to ensure that it is not a question of acute IOP increase in a case of advanced PAC requiring a different therapy. Thereafter, control examination should be performed annually.

As mentioned above, cases of abortive subacute PAC with prodromal symptoms (rainbow coloured haloes, blurred vision and frontal headaches) are frequently seen. Early diagnosis and treatment can be performed by the observant ophthalmologist.

D

Contrary to general assumption, asymptomatic, “creeping” chronic PAC (angulus clausus chronicus) with pupil block is more common than acute PAC17, and this represents one of the most important arguments for carrying out PAC detection using LCD assessment. The term “chronic” refers to the identification of permanent structural changes in the form of PAS, but here only involving < 50% of the angle circumference (fig. 21). This means that the remaining angle drainage will generally be adequate to maintain normal eye pressure without any treatment. It is to be emphasized that the occurrence of a single but definite PAS formation in the upper angle should be considered as represent-

62 Main groups and subclassification of PAC

ing a solid basis for chronic PAC diagnosis and consequently an indication for treatment.

The treatment consists of YAG-laser iridotomy (fig. 21), and the patient can be informed before laser treatment that the treatment in itself will probably be curative.

Apart from control the day following laser treatment, the patient should be checked after 1, 3 and 6 months. Then generally annually in order to ensure that it does not represent a case of latent PAC glaucoma. Post-laser gonioscopic examination is especially indicated in border-line cases as it then becomes much easier to determine the degree of PAS development and thereby the risk of development of permanent pressure elevation.

E

In latent PAC glaucoma (glaucoma angulo clauso latens) with pupil block the untreated eye pressure is permanently ≥ 24 mmHg due to PAS formations in 50 to 80-90% of the angle circumference. There are, however, no structural glaucoma changes in the posterior pole, no functional glaucoma defects and most often without subjective symptoms. If the gonioscopic assessment has been correct, the eye pressure will, also following YAG-laser iridotomy, remain permanently increased with the risk of the development of structural/functional defects, i.e. manifest glaucoma. Due to the combined risk factors (ocular hypertension + PAS), this risk is considered to be large enough to warrant permanent, prophylactic, medical IOP reduction, notably only without the use of pilocarpine (fig. 21).

As with POAG, it is advisable to check the patient at regular intervals of 4-5 months with special emphasis on the gonioscopic assessment of the degree of development of PAS.

In most cases, the latent PAC glaucoma will develop subclinically from asymptomatic “creeping” chronic PAC, leading to a risk of misdiagnosis, often in the form of latent POAG with consequent unspecific treatment in the form of various non-miotic eye drops. It is important to stress that such treatment does not prevent a continued development of PAS with a gradually increasing pressure and consequently a risk of manifest PAC glaucoma or neovascular glaucoma. The importance of routine LCD assessment followed by ACD measurement and standardised PAC gonioscopy at the slight-

64 Main groups and subclassification of PAC

est suspicion of PAC should be emphasized. The examination of the healthy eye is particularly important in this connection. This is illustrated in the case report below (case report 1).

In some cases, asymptomatic latent PAC glaucoma, especially during the later course, will lead to subacute IOP increase with subjective symptoms in the form of slight blurring of vision and frontal headaches, but usually without corneal oedema. Consequently, with an inadequate gonioscopy without pre-laser observation of the PAS formation, there is a risk that the condition will be seen as a first-time case of subacute PAC followed by use of unspecific treatment.

F

Manifest PAC glaucoma (glaucoma angulo clauso manifestus) with pupil block refers to the PAC development stage in which structural changes to the optic nerve and the retinal nerve fibre layer are seen, often combined with visual field defects. The untreated IOP is high (> 30 mmHg) as a result of PAS involving > 80-90% of the angle circumference, but most often the condition is without subjective symptoms.

When PAS can be identified in the entire angle circumference (approx. 360 degrees) with a reasonable degree of certainty, then neither YAG iridotomy nor cataract removal (without simultaneous trabeculectomy) can be expected to result in any form of pressure reducing effect, but rather lead to a further pressure rise due to increased inflammation and consequently with a poorer prognosis for a fistulating operation. This is partly due to the fact that it is not possible to disrupt fibrozised PAS by means of an iridotomy or by removing the lens and partly due to the fact that the remaining, functioning trabecular meshwork may become occluded by iris particles formed through either laser treatment or from viscoelastic material and inflammation precipitates in association with a cataract operation. At this stage of development of the disease process, it is only advisable to perform an iridotomy or remove a cataract when indentation gonioscopy shows a high degree of uncertainty as to the degree of spreading of PAS, and only when the patient has been given maximum drug treatment. Furthermore, the degree of glaucomatous loss of tissue in the nerve head may be used as a guideline since a C/D ratio of 0.9

Main groups and subclassification of PAC 65

in the affected eye will almost always be accompanied by PAS in most of the circumference. The same applies to the occurrence of tunnel vision in automatic perimetry, which is why this examination should also generally be carried out prior to the planning of the final treatment.

In terminal PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) YAG-laser iridotomy or removal of the lens without simultaneous filtrating operation is therefore contraindicated.

It must therefore be stressed that a reasonably adequate ophthalmoscopic optic nerve assessment should always be carried out prior to laser treatment. This will involve use of 50% glucose in order to clear the cornea and possibly pupil dilatation with 2.5% metaoxedrine drops because of drug miosis (pilocarpine treatment).

When a peak pressure > 20 mmHg despite maximum drug treatment including use of pilocarpin is observed, or when the patient cannot handle the treatment using three eye drop medications (the definition of maximum treatment), a fistulating operation should be performed (in case of cataract combined phaco-MMC- trabeculectomy). Only one clinical retrospective examination concerning this has been reported33. YAG iridotomy operations were performed on eyes with manifest PAC glaucoma, but in all cases there was an indication for continued medical treatment, and in more than 1/3 a filtrating operation was required.

Especially in connection with PAC glaucoma with pupil block the risk of post-operative ciliary block (formerly known as malignant glaucoma) may be increased (ref: Treatment procedure: Fistulating operation). If the pressure is acceptable on maximum treatment (including pilocarpine), the patient should then remain on the medication. For the same reason, in cases where IOP > 20 mmHg in an only eye with terminal manifest PAC glaucoma, transscleral diode-laser cyclophotocoagulation is recommendable instead of a fistulating operation.

As with latent PAC glaucoma, with manifest PAC glaucoma there may occasionally be subacute IOP increase with frontal headaches and slight blurring of vision, however with an almost clear cornea. This situation may be misinterpreted as a true attack of acute glaucoma with the indication for a “curative” iridotomy and so resulting in unspecific treatment.

Main groups and subclassification of PAC 67

Subacute, pressure conditioned subjective symptoms caused by juvenile open-angle glaucoma may also be misinterpreted as prodromal symptoms of acute PAC. Blurring of vision, rainbow coloured haloes and headaches are common in juvenile glaucoma16, and since goniodysgenesis, often with pronounced iris processes, is also typically seen in this form of glaucoma16 the condition may be misinterpreted as acute aggravation of manifest PAC glaucoma with diffuse PAS formation (ref: Normal anatomy of the chamber angle, The uveal meshwork). Case report 2 is an example of this.

YAG-laser iridotomy: Evaluation

The need for preventive YAG-laser iridotomy should be firmly established before undertaking the procedure, with a precise evaluation not only of the effect, but also of any possible complications.

As previously mentioned, gonioscopic detection of a pupil block conditioned PAC risk anatomy does not necessarily mean that the patient in question will develop a manifest disease.

In an American multi-centre study17 129 patients with PAC risk anatomy were monitored for up to six years without treatment, and during this period only 25 patients (38 eyes) developed manifest PAC, i.e. approx. 20% of the patients at risk. In a recent study from India43 a similar risk of progression was found (22% of eyes with occludable angles in 180 degree or more developed manifest PAC after 5 years).The estimated risk of developing manifest glaucoma in the individual eyes at risk within a period of five years was estimated at 30% (Kaplan-Meier analysis)17. Furthermore, it was concluded that the most predictive method for identifying the eyes that later developed manifest PAC was the slit lamp and gonioscopy examination carried out by the experienced ophthalmologist17.

The second-best method was axial chamber depth measurement as the eyes that were developing manifest PAC had a shallower chamber depth than the eyes at risk that did not develop symptoms17. This was not, however, significant.

The provocation test in the form of dark-room test – prone position (ref: Dark-room test – prone position, Diagnostic methods with PAC) was, however, only positive in 24% of the eyes which later developed manifest PAC. Therefore it was concluded that

68 Main groups and subclassification of PAC

the method cannot generally be recommended as a predicative test for an iridotomy17.

Even though no predicative method with the desired sensitivity with respect to iridotomy indication exists, the conclusion of the study was that preventive laser treatment should be recommended for all patients with a gonioscopically verified risk anatomy17. A similar attitude was clearly expressed in 199618, 19.

According to the above-mentioned statement18, 19, PAC risk anatomy is found among 5% of the population, whereas the prevalence of manifest glaucoma is 0.6%34. The situation can therefore be compared with open-angle ocular hypertension, which is found among approx. 10% of the population and primary open-angle glaucoma with a general prevalence of 0.65% in Denmark20. The guidelines concerning treatment of primary open-angle glaucoma (POAG)21 given by the Danish Glaucoma Society therefore only recommend treatment of latent POAG (without structural/functional defects) with a view to preventing manifest POAG when combined risk factors are present (ocular hypertension and inheritance, now updated with thin corneas, larger Cup-Disc ratios and older age groups according to the Ocular Hypertension Treatment Study45).

Accordingly, in connection with PAC, the application of combined risk factors in the form of a narrow angle with the standardised PAC gonioscopy methodology and an axial chamber depth of ≤ 2.0 mm is therefore recommended. This recommendation is based on the fact that pupil block conditioned PAC, as mentioned in the section concerning axial chamber depth measurement, is predominantly found in eyes with an ACD ≤ 2.0 mm. In this way, the diagnostic basis for imminent PAC is further enhanced, making the indication of preventive YAG-laser iridotomy more precise.

This is especially relevant in bilateral PAC, whereas the occurrence of acute PAC in the first eye creates a clear indication for preventive laser treatment of imminent PAC in the other eye since acute PAC episodes will otherwise occur in 50-75% of these eyes within five years.

With respect to the effect of the prophylactic iridotomy, the laser treatment effectively eliminates the risk of angle-closure as the relative pupil block, and thereby the pathogenic basis for PAC, is removed18.

Main groups and subclassification of PAC 69

Even though the indication and the effect of YAG-laser iridotomy thus seem to be clarified, proper use requires that serious complications be avoided.

As opposed to argon-laser iridotomy, no laser-conditioned focal cataract changes have been described with YAG-laser iridotomy22, but on the basis of a theoretical risk it is recommended that the iridotomy be placed as peripherally as possible on the iris.

The most frequent complication is temporary haemorrhage from the iridotomy opening. This is seen in up to 44%22, but the bleeding will cease spontaneously and can be reduced by indentation with the contact lens used. Only in cases on anticoagulation treatment or with acetylsalicylic acid medication does a sedimented hyphaema occur, and this treatment should therefore be discontinued for some weeks before laser application. 32% of eyes with haemorrhage have an IOP increase of > 10 mmHg within the first three hours after the laser treatment, but the corresponding figure for eyes without bleeding is 33%22, i.e. the bleeding does not accentuate the occurrence of post-laser increase in pressure. As stated in the chapter concerning treatment procedures, one pre-laser application with apraclonidine (Iopidine®) drops will, as well as preventing any post-laser increase in pressure, also reduce the occurrence of bleeding due to the vasoconstrictive properties of the substance. The patient should therefore receive the eye drops before the laser treatment.

Otherwise no serious complications occur (ref: YAG-laser iridotomy, p. 102), and consequently it can be concluded that the advantages of preventive YAG-laser iridotomy with imminent PAC clearly outweigh the disadvantages, and the treatment can therefore be recommended.

YAG-laser iridotomy in general

The recommended technique for YAG-laser iridotomy is described in the chapter concerning treatment procedures, and therefore only the more general conditions will be discussed in this chapter.

There has been a tendency to perform several iridotomies in the same eye just to be on the safe side! However, there is no rational basis for this.

According to Hagen-Poiseuilles’ law, an opening of about 60 microns should compensate for the normal aqueous flow23. A stro-

70 Main groups and subclassification of PAC

mal iridotomy opening of about 150 microns should thus be fully adequate to neutralise the pressure gradient between the anterior and posterior chambers in pupil block conditioned PAC22,24.

It is possible to obtain an impression of the size of the iridotomy opening by projecting the 0.2 mm “spot” from a Haag-Streit slit lamp on the iridotomy or by using the 100 micron “aiming spot” from the argon-laser. Apart from a stromal hole of > 100 microns, adequate iridotomy function also requires an opening through the iris pigment epithelium. This is ensured by means of co-axial slit lamp illumination immediately after laser treatment. As opposed to argon-laser iridotomy there is no post-laser occlusion after YAG-laser iridotomy in PAC22.

By performing several iridotomies there is an additional risk that one of the iridotomies will be situated in the rima area and thus may create visual disturbances for the patient. It should therefore be recommended that a single iridotomy is placed in the peripheral iris area covered by the eye-lid in the upper direction. To ensure the peripheral localisation, 2% pilocarpine eye drops are used before laser treatment (also see: YAG-laser iridotomy technique).

GROUP II: PAC WITH PLATEAU IRIS

The classification criteria for this PAC group are seen in fig. 18, which illustrates the main classification of PAC.

As previously stated, eyes with plateau iris probably constitute at the most 10% of the PAC population according to clinical opinion15, and of this group eyes without a pupil block component, i.e. purely plateau iris conditioned pathogenesis, probably only constitute 25%25.

However, it should be emphasised that there are no prospective population studies concerning the prevalence of plateau iris conditioned PAC, partly because there is no generally accepted definition of this PAC group. Consequently, it is quite likely that the prevalence of this group is considerably larger than generally assumed. Moreover, as the specific treatment of this group solely involves argon-laser iridoplasty, the correct diagnosis is a prerequisite for a satisfactory course of treatment.

PAC with plateau iris is most frequently seen in women between 30 and 50 years15. The gender ratio is F/M: 3/125, i.e. the same gender

Main groups and subclassification of PAC 71

distribution as in PAC with pupil block, whereas the occurrence of hypermetropy is probably less prevalent.

Pathophysiology and pathogenesis

The pure plateau iris configuration refers to a pathoanatomy with narrow angle, but with normal axial chamber depth (ACD ≥ 2.5 mm) as is seen in the main classification figure (fig. 18, p. 51). The angle is narrow because of two conditions as is seen in fig. 22.

Fig. 22. PAC with plateau iris: Undilated/dilated pupil.

First of all, the iris is inserted right at the anterior edge of the ciliary body directly behind the scleral spur, i.e. the iris stroma often covers the longitudinal fibres of ciliary muscle (the ciliary band) on their course to the scleral spur. This implies that the normal angle recess (the most peripheral point of the chamber angle) is small and that it is more difficult to identify the ciliary band than in PAC with pupil block (cf. fig. 20 and fig. 22).

Secondly, the iris is flat and almost immobile with an angled iris root, which makes the iris knee abnormally prominent and impossible to level out by means indentation gonioscopy (fig. 14). This means that the visualisation of the normal angle structures remains unimproved on indentation gonioscopy, which is quite the opposite to pupil block conditioned PAC (ref: Iris contour and mobility, p. 33).

72 Main groups and subclassification of PAC

Fig. 23. UBM with typical plateau iris anatomy in spite of iridotomy (top, left picture) in a patient (case report 7) with chronic PAC with PAS (lower, right picture). P. Kock Jensen and Lars Solander, the Glaucoma Clinic, Copenhagen University Hospital.

Due to this special pathoanatomy, a semi-dilated pupil can lead to angle-closure (e.g.: darkened room).

The pathogenesis for this anatomy is probably a prominent anteriorly positioned ciliary body7 as shown in the UBM pictures in fig. 23. These ultrasound pictures are taken of a patient with recurring subacute attacks in spite of YAG-laser iridotomy (case report 7). The top left picture shows the flat iris with the typically prominent iris knee, which makes the angle narrow occludable in spite of the perfect penetrating iridotomy.

It should therefore be strongly emphasized that YAG iridotomy is completely ineffective in the plateau iris condition.

All four pictures show an anteriorly positioned ciliary body as indicated with the arrow in the top right picture, whereas the bottom left picture shows an additional iris/ciliary body cyst. These cysts are almost always seen in plateau iris and are probably secondary to the narrow space in the posterior chamber.

The anteriorly positioned ciliary body is the reason for the immobility of the iris periphery on indentation gonioscopy (chock

Main groups and subclassification of PAC 73

effect) as opposed to the situation in connection with pupil block conditioned PAC. Here, the pathogenetic aqueous fluid in the posterior chamber is easily pushed away on indentation gonioscopy, leading to the typical extreme iris mobility for this PAC group (see fig. 14).

The gonioscopic assessment of iris contour and mobility is, apart from axial chamber depth measurement, the most important differential diagnostic parameter for distinguishing between pupil block or plateau iris conditioned PAC.

In connection with a pronounced plateau iris configuration where the iris knee is in line with Schwalbe’s line over the entire circumference, either spontaneous or drug-induced pupil dilatation will lead to complete appositional angle closure with acute PAC (fig. 23). However, this situation is only seldom seen15. Far more commonly, the undulating configuration of the iris knee will lead to an incomplete iris/ meshwork apposition situated at the tops of the wave crests. This pathoanatomy causes a ”creeping” PAS formation, i.e. asymptomatic PAC.

Thus, asymptomatic, “creeping” angle-closure is probably far more common in connection with plateau iris than with PAC with pupil block, i.e. it is seen in most cases of plateau iris conditioned PAC15.

It is especially important with plateau iris that gonioscopy is performed under dimmed illumination and using a narrow, low aperture slit beam. The reason for this is that any light-condi- tioned miosis, especially in plateau iris, will increase the risk of overlooking narrow angle anatomy (ref: Standardised PAC-goni- oscopy methodology).

Detection and diagnosis

Evaluation of the limbal chamber depth (LCD) is, as in PAC with pupil block, the preferred method of detection. It is important to note that with plateau iris the LCD in some cases lies between 0.25 and 0.5, which is greater than the previously established risk factor of 0.25 (ref: LCD methods, p. 13). In detection of plateauiris conditioned PAC it is especially important to perform routine

74 Main groups and subclassification of PAC

gonioscopy with a Posner lens when there is the slightest suspicion of a relative narrow chamber angle following LCD estimation.

The diagnosis of a plateau iris configuration is relatively simple as it is purely based on the previously described characteristic pathoanatomy. The gonioscopic evaluation regarding the narrowness of the angle is, however, often much more difficult when compared to the pupil-block type. This is primarily due to the poor visibility of the trabecular meshwork and the ciliary band. In this younger group of patients the meshwork is less pigmented, and the ciliary band is often partially hidden by the iris stroma and the uveal meshwork. Furthermore, the undulating iris knee will often create the opportunity of identifying the trabecular meshwork in certain “wave-bottoms”. Diagnosis of a narrow angle with a plateau iris requires a greater degree of judgement than in PAC with pupil block. As has been emphasised, a dimmed room illumination and the weakest possible slit-lamp light are required for proper detection.

Moreover, with the pure plateau iris form of PAC the normal ACD (≥ 2.5 mm) provides no diagnostic assistance.

Therefore, in case of imminent PAC with plateau iris a positive dark-room test may be used in addition to the gonioscopy as an indication for treatment (see below).

The necessity of using two diagnostic procedures with regard to proper diagnosis and indication for treatment concur with the previous statements made (ref: Main classification and methods of classification).

A negative dark-room test in the presence of a gonioscopically suspect plateau iris configuration does not necessarily imply that the patient can be exempted from further investigations as the predictive value of a dark-room test is limited (ref: YAG-laser iridotomy: Evaluation, p. 67). However, there are no investigations regarding the predictive value of the dark-room test in PAC with plateau iris. It is to be recommended that such patients be observed without treatment until such times that either PAS or prodromal symptoms develop.

Even though ACD measurements are without diagnostic significance with the pure plateau iris, it is to be noted that the examination is necessary from the differential diagnostic point of view with regard to specific treatment. A normal anterior chamber depth excludes a pupil-block component and the indication

76 Main groups and subclassification of PAC

A

In suspect PAC (suspicio angulo clauso) with plateau iris the angle is narrow occludable in the upper sector, but not the lower. As mentioned in the section: Detection and diagnosis, the gonioscopic assessment with regard to narrow angle is more difficult in plateau iris conditioned PAC than in the pupil block form. Therefore, if in doubt, a dark-room test may be carried out in order to give as accurate a diagnosis as possible.

Control without treatment is recommended after the patient has been thoroughly informed about glaucoma prodromal symptoms. Generally, control should be carried out after 6-12 months

– naturally sooner should subjective symptoms occur.

B

In imminent PAC (angulus clausus imminens) with plateau iris the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower, but without PAS. Apart from gonioscopy, a positive darkroom test is generally required, because of the normal ACD and the difficulty with regard to the visibility of the trabecular meshwork (ref: Detection and diagnosis). Not until the diagnosis has been verified is it possible to decide on a preventive iridoplasty, since especially this form of laser treatment requires a precise indication due to the higher incidence of complications than with YAG-laser iridotomy (ref: Argon-laser iridoplasty: Evaluation, p. 80). Case report 3 is an example of initial misdiagnosis caused by the above-mentioned conditions with an unspecific treatment. This is, however, followed by a clarification by utilising the procedure as described.

Because of the frequent presence of LCD limit values in plateau iris, the detection of early PAC cases in this main group remains less than in the pupil block group, and the degree of detection is dependant upon the use of gonioscopy even at the slightest suspicion of LCD. Precisely in this situation the more efficient gonioscopy with the Posner lens has many advantages as opposed to the more time-consuming and discomforting gonioscopy using the Goldmann lens.

Main groups and subclassification of PAC 77

Case report 3

Imminent PAC with plateau iris

A 66-year-old female with initially detected IOP 28 mmHg right eye and subsequent timolol gel and latanoprost treatment is referred because of the limit pressure and increasing visual field defects.

Anterior chamber was described as slightly flattened peripherally, deep centrally and open angle on gonioscopy, however with a slight plateau appearance! Because of suspicion of increasing visual field defect in spite of normal IOP on the prescribed treatment, ALT was carried out on the right eye. Because of temporary IOP of 26 mmHg in both eyes 14 days post-laser, the patient was referred to the Glaucoma Clinic due to “unmanageable glaucoma”.

LCD: 0.25 right eye. > 0.25 left eye, ACD 2.5/2.6 mm. Untreated IOP < 24 mmHg. On gonioscopy: Narrow occludable angle without PAS, plateau iris with poor motility and typical peripheral iris knee. On ophthalmoscopy.: Ratio: 0.5/0.3 without certain loss of tissue. With diurnal curve untreated IOP < 24 mmHg was found. Positive prone, dark-room test (17/16 mmHg before, 28/24 mmHg after).

Automatic perimetry did not show clear glaucoma changes.

Treatment: Bilateral argon-laser iridoplasty

Followed by normal eye pressure with negative dark-room test.

Comments

Reason for unspecific treatment:

Incorrect glaucoma classification (primary open-angle glaucoma instead of PAC) due to inadequate gonioscopy.

Outcome of unspecific treatment:

1.Prolonged process (approx. 6 months) with treatment for simplex glaucoma and temporary pressure rise because of angle closure.

2.Unnecessary argon-laser trabeculoplasty because of the above-mentioned diagnoses.

C

In Acute/subacute PAC (angulus clausus acutus/subacutus) with plateau iris the clinical symptoms and signs are exactly the same as seen in the pupil block form. As in the acute pupil block form, it should be emphasized that it is important to carry out the objective examination of the healthy eye before examining the affected eye with a view to establishing a reliable diagnosis. Furthermore, the examination of the healthy eye will generally lead to an in-

78 Main groups and subclassification of PAC

dication for preventive iridoplasty due to imminent PAC with plateau iris.

Following pressure reducing acute medical treatment (ref: Treatment procedures with PAC) argon-laser iridoplasty is carried out. In contrast to YAG iridotomy this treatment can be carried out regardless of a cloudy cornea.

D

Asymptomatic “creeping” chronic PAC (angulus clausus chronicus) with plateau iris is probably seen far more often than the acute form, especially in main group II. Therefore, active detection by means of LCD and efficient indentation gonioscopy with the Posner lens is particularly important in connection with this subgroup. The term “chronic” as in chronic PAC with pupil block refers to the presence of PAS formations in < 50% of the angle circumference (fig. 24), i.e. the remaining trabecular meshwork function is usually adequate in order to maintain normal IOP without pressure lowering medical treatment.

Thus, the diagnosis at this phase of development provides the opportunity for primary specific iridoplasty without the need for post-laser medical treatment. Therefore, the patient can be given pre-laser information that the laser treatment will most likely be curative. Control is advised the day after laser treatment and 1, 3 and 6 months later with respect to supplementary iridoplasty, which is often necessary in order to obtain maximum angle opening. Following this, the patient is seen once a year for a gonioscopic assessment of the iridoplasty effect as supplementary laser treatment may be necessary with some patients (ref: Argon-laser iridoplasty: Evaluation).

It should be stressed that YAG laser iridotomy does not change the angle anatomy. Case report 4 illustrates the typical subclinical course as well as the lack of effect of YAG laser iridotomy in group II.

E

In latent PAC glaucoma (glaucoma angulo clauso latens) with plateau iris the untreated IOP is permanently ≥ 24 mmHg because of PAS formations in 50% to 80-90% of the angle circumference,

Main groups and subclassification of PAC 79

Case report 4

Bilateral chronic PAC with plateau iris

A 71-year-old man with untreated Goldmann applanation 28/26 mmHg without subjective symptoms and with occludable angles with plateau characteristics as well as normal optic nerve heads, receiving Dorzolamide treatment, was referred for YAG-laser iridotomy.

Goldmann applanation.: 22/22 mmHg on dorzolamide treatment, angles narrow, occludable in the upper/lower areas, no PAS but plateau characteristics with LCD 0.25 both eyes, ACD 2.7 mm both eyes and C/D ratio 0.4/0.5 without certain structural changes.

Due to untreated IOP 23 mmHg right eye, the patient was referred to the Glaucoma Clinic.

Diagnosis given by the Glaucoma Clinic: Bilateral chronic PAC with plateau iris.

LCD 0.25 both eyes and ACD 2.6 both eyes. In spite of adequate bilateral iridotomies, narrow, occludable angles with immobile irides with iris knee and PAS in the upper area were found in both eyes as well as C/D ratio 0.6/0.5 without structural changes, and normal visual fields with automatic perimetry.

Followed by diurnal curve showing: peak pressure 19/18 mmHg, without medical treatment, i.e. satisfactory untreated situation. Control was recommended at the local ophthalmologist one month later for potentially further iridoplasty treatment.

Comments

Reason for unspecific treatment:

1.Uncertain Goldmann gonioscopy with a suspicion of plateau iris, but no Posner lens gonioscopy with regard to PAS and iris mobility assessment.

2.No consequence of the ACD measurement.

Outcome of unspecific treatment:

Unnecessary YAG iridotomy with unchanged post-laser narrow angle instead of primary argon-laser iridoplasty, i.e. patient-stressing “trial and error” course.

but without structural glaucoma changes in the posterior pole and without visual field defects. Even after satisfactorily performed primary iridoplasty the IOP will still be permanently increased. Because of the risk of the patient developing manifest glaucoma,

80 Main groups and subclassification of PAC

permanent medical treatment is therefore still indicated. In most cases, the use of pilocarpine is, as opposed to the situation concerning pupil block, necessary to ensure IOP < 20 mmHg (ref: Argon-laser iridoplasty: Evaluation). As in POAG, pressure and gonioscopy control is advised every four to five months.

The latent PAC glaucoma with plateau iris will probably develop asymptomatically with “creeping” PAS formation to a higher degree than with pupil block conditioned glaucoma. Together with LCD values between 0.25 and 0.5, the risk of misdiagnosis in the form of latent POAG is therefore especially high in plateau iris conditioned glaucoma. This misdiagnosis can only be avoided through routine gonioscopy with the Posner lens in all glaucoma cases. It is important to stress that medical pressure reduction without miotics does not prevent continuing PAS formation.

As in asymptomatic latent PAC glaucoma with pupil block, an asymptomatic case of latent PAC glaucoma with plateau iris can sometimes lead to subacute subjective symptoms in the form of slight blurring of vision and fleeting rainbow haloes with frontal headaches. This may thus mistakenly be perceived as representing a case of genuine acute glaucoma, maybe even pupil block conditioned!

F

In manifest PAC glaucoma (glaucoma angulo clauso manifestus) with plateau iris the angle is closed by PAS in > 80-90 degrees of the circumference, the untreated IOP (peak pressure) is permanently ≥ 24 mmHg, there are structural optic nerve and retinal changes and usually visual field defects (fig. 24).

In connection with the typical asymptomatic manifest glaucoma there may sometimes be subacute subjective symptoms (blurring of vision and frontal headaches) in connection with pressure elevations as is the case in latent

Argon-laser iridoplasty: Evaluation

There are surprisingly few publications of the effect of iridoplasty with plateau iris.However, the application of argon-laser iridoplasty has increased throughout recent years and is now also recommended for acute PAC with pupil block when it is technically not possible to carry out YAG laser iridotomy26.

82 Main groups and subclassification of PAC

Comments

Reason for unspecific treatment:

1.Neither the patient’s own ophthalmologist nor the referring eye department undertook a mainand subclassification of PAC since assessment of both iris mobility and PAS was omitted. No consequence was taken from the ACD measurement or the degree of C/D ratio.

2.A diurnal curve was not carried out until four months later at which stage normal IOP left eye was measured at 8:30 am and 12:15 pm (14 and 15 mmHg, respectively), however with an unacceptable pressure top in the evening (24 mmHg), i.e. not until this stage is it possible to adequately treat the terminal situation on the left eye.

Outcome of unspecific treatment:

1.Laser treatment with a “trial and error” course instead of primary maximal drug treatment, which was not started until five months later!!!!

2.Additional IOP elevation after YAG-laser iridotomy and argon-laser iridoplasty because of terminal PAC glaucoma.

3.Neovascular glaucoma right eye.

In a prospective study from 1988 the effect of iridoplasty on imminent and chronic PAC as well as latent PAC glaucoma with plateau iris was evaluated on the basis of post-laser IOP and prone dark-room test25. The darkroom test was carried out without the pre-laser required pilocarpine treatment. The diagnostic and classification criteria were similar to those mentioned in this book. During an observation period of a minimum of six months without pilocarpine treatment, the dark-room test remained negative and untreated IOP was normal in 100% of all cases with imminent PAC. In chronic PAC pilocarpine was dispensable in 90% of all cases, whereas this was only the case in 55% of the cases with latent PAC glaucoma. The study thus demonstrates a sufficient effect of iridoplasty, however first and foremost in the early stages without PAS (imminent PAC) or PAS in < 50% of the angle circumference (chronic PAC). The necessary post-laser drug treatment in latent PAC glaucoma with plateau iris must therefore often include pilocarpine as opposed to the situation in latent PAC glaucoma with pupil block (see p. 62). When in doubt it is advisable to carry out a prone dark-room test.

The long-term effect of iridoplasty in early plateau conditioned PAC with continued iris/cornea contact following iridotomy has recently been reported by Ritch, Tham and Lam27. Estimated on the basis of the clinical situation (IOP and gonioscopy) after six years in 23 eyes among 14 patients, the angle-opening laser-effect was still sufficient in 87% of the eyes after one iridoplasty treatment. Repeated treatment was necessary in the remaining three eyes

Main groups and subclassification of PAC 83

after a few years. The examination thus indicates that the effect of iridoplasty is long-lasting in most eyes, but decreases in some cases with the indication for further treatment. Continued control (e.g. once a year) is therefore recommended after iridoplasty. This is the opposite of the case following YAG-laser iridotomy in early PAC with pupil block where the laser effect permanently excludes angle-closure (ref: YAG-laser iridotomy: Evaluation, p. 67).

Post-laser complications are seen more frequently following iridoplasty than with YAG-laser iridotomy. In most cases, there is a minor intraocular reaction requiring local steroid treatment as well as the withdrawal of any pre-laser pilocarpine treatment. In many cases, a lesser degree of permanent pupil dilatation is seen, however only seldom does a laser-conditioned pressure increase occur in contrast to YAG-laser iridotomy. Extra powerful laser applications may lead to iris pigment hypertrophy around the laser burns. However, no serious complications such as cataract development or intra-ocular haemorrhages are seen.

We therefore find there is a clear indication for iridoplasty with imminent PAC, acute/subacute PAC, chronic PAC as well as latent PAC glaucoma when the patient meets the diagnostic criteria as described above.

In terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision), iridoplasty is not advised due to the risk of post-laser pressure increase (ref: Manifest PAC glaucoma with plateau iris).

Argon-laser iridoplasty in general

With respect to iridoplasty technique, one is referred to the section concerning treatment procedure, iridoplasty. It should, however, be stressed that it is advisable to determine the required energy amount (immediate visible iris shrinkage) in each individual patient by “titration”, always starting with a low energy position (100 mW). This is essential not only in order to avoid micro-explosions (bubble formation), but also because the required energy application is close to the pain threshold of many patients.

Furthermore, the application of a lengthy exposure time (0.5 seconds) is often disturbing to the patients with respect to the required fixation. This is especially the case when indirect laser application via an angular mirror is used. Treatment is much easier to carry

84 Main groups and subclassification of PAC

out for all parties involved when direct laser application on the iris root is performed using an Abraham iridotomy lens. This lens has an adequate and not too large a magnification when compared to the Wise iridotomy lens.

GROUP III: PAC MIXED GROUP (I+II)

The occurrence of the grey transition cases found between the pure clinical entities is, as is well known, a challenge to the clinician. The main group III, which appears more frequently than the pure plateau cases, is a good example of this, as the pathoanatomy includes conditions of group I as well as group II. Here, a satisfactory course without unexpected treatment frustrations both for the ophthalmologist and for the patient can only be achieved when the patient has been correctly classified from the start. After this, the patient can be prepared for the possibility of a more complicated treatment course, including the application of both YAG-laser iridotomy and argon-laser iridoplasty.

Again, the application of ACD is of decisive importance. As illustrated in fig. 18, main classification of PAC, gonioscopy shows varying degrees of both pupil block and plateau iris pathoanatomy. If the chamber angle anatomy is the only guideline used, it will often lead to incorrect placement into either group I or II. An ACD ≥ 2.1 mm and ≤ 2.4 mm may be used as a guideline since these ACD values lie between those found in typical cases of pupil block and the normal ACD values found with a pure plateau iris.

Pathophysiolology and pathogenesis

See the corresponding section under Group I: PAC with pupil block and Group II: PAC with plateau iris, respectively.

Detection and diagnosis

Detection is carried out by means of LCD, which is most often < 0.25 in this group. The actual diagnosis is made using “the mixed gonioscopy” findings together with ACD values between ≥ 2.1 mm and ≤ 2.4 mm.

Main groups and subclassification of PAC 85

Subclassification with specific treatment and case reports

As in the other main groups, the various development stages of the PAC mixed group require different forms of treatment. Therefore, a subclassification indicating the specific treatment regimes for each individual subgroup must be carried out. The terminology and definitions of the individual subgroups are the same as in I and II.

The subdivision and the specific treatment are illustrated in fig. 25.

Fig. 25. Subclassification of Group III: PAC mixed group II+II) and specific treatment.

A

In suspect PAC (suspicio angulo clauso) mixed group the angle is narrow occludable in the upper sector, but not in the lower and with a varying degree of gonioscopic pupil block/plateau iris

86 Main groups and subclassification of PAC

components. The axial chamber depth measurement shows values between those of the pure pupil block (I) and plateau iris (II) group (≥ 2.1 mm and ≤ 2.4 mm). Once the patient has been informed regarding glaucoma prodromal symptoms, control without treatment should be carried out every 6-12 months.

B

In imminent PAC (angulus clausus imminens) mixed group the angle is narrow occludable or appositional closed in the upper sector and occludable in the lower with a varying degree of gonioscopic pupil block/plateau iris anatomy as well as ACD ≥ 2.1 mm and ≤ 2.4 mm. There are no PAS in the chamber angle, normal untreated IOP and no structural nerve head/retinal changes or functional defects. The condition is thus asymptomatic and can only be detected by means of LCD < 0.25. Because of the pupil block component, the gonioscopic interpretation with respect to narrow occludable angle is usually easier than in the pure plateau iris situation. It is generally not necessary to carry out a supplementary dark-room test.

The preventive, primary treatment is YAG-laser iridotomy. However, prior to the YAG-laser treatment the patient should be informed about a possible need for a subsequent iridoplasty. This is carried out if LCD does not change considerably and if the angle remains narrow occludable or appositional closed in the upper sector and ocludable in the lower. It should be emphasised that “post-YAG” gonioscopy with regard to the indication for argon-la- ser iridoplasty should preferably be carried out the day following the YAG-iridotomy in order to prevent a plateau iris conditioned acute PAC.

A post-YAG elevation in IOP does not necessarily indicate the need for iridoplasty. The indication for this should solely be based on the gonioscopic pathoanatomy, especially noting the difference in the iris mobility between pupil block and plateau iris situations. Case report 6 is an example of this. If the eye pressure after YAG is normal, but the angle still seems to be narrow occludable with a plateau configuration, in case of doubt, a prone dark-room test should be performed to determine the necessity for an iridoplasty. Post-laser control is recommended after 1, 3 and 6 months and then annually.

Main groups and subclassification of PAC 87

C

The medical treatment of acute/subacute PAC (angulus clausus acutus/subacutus) mixed group is similar to that of the acute cases of pure pupil block or plateau iris (ref: Treatment procedures with PAC, p. 95).

As mentioned earlier in acute PAC, the diagnosis should primarily be established by examining the healthy eye, which should then be treated preventively (pilocarpine and laser treatment). As soon as possible YAG-laser iridotomy of the acute eye is carried out with post-laser LCD and gonioscopic assessment with regard to indication for iridoplasty. This assessment should be carried out at the latest the day after YAG-laser treatment in order to avoid a new attack. In doubtful cases, a dark-room test should be carried out. Both the post-laser gonioscopy and the dark-room test should be undertaken on eyes not receiving any medications, especially pilocarpine.

Post-laser control without drug treatment should be carried out after 1, 3 and 6 months and then annually.

D

As in the corresponding subgroups in main group I and II, asymptomatic “creeping” chronic PAC (angulus clausus chronicus) mixed group is probably more common than acute/subacute PAC, which is why the importance of detection by means of LCD should once again be stressed.

As in I and II, the term chronic refers to the presence of permanent structural changes in the form of PAS, but in < 50% of the angle circumference, which is why the untreated IOP remains normal (fig. 25).

As in B and C, the patient may prior to treatment be informed that the treatment will probably be curative, but may possibly require the application of both YAG-laser and argon-laser therapy. As mentioned in C, this decision should be made the day following YAG-laser iridotomy in an untreated eye. As appears from case report 7, omission of this may lead to a frustrating and lengthy treatment course.

Finally, post-laser control without drug treatment is recommended after 1, 3 and 6 months and then annually.

Main groups and subclassification of PAC 89

E

In latent PAC glaucoma (glaucoma angulo clauso latens) mixed group IOP is permanently ≥ 24 mmHg due to PAS in > 50%

– < 80-90% of the angle circumference, but there are no structural glaucoma changes in the posterior part of the eye, and there are no functional defects. Even following sufficient laser treatment, permanent pressure reducing drug treatment is therefore necessary in order to prevent the development of manifest PAC glaucoma.

As in I and II, an asymptomatic “creeping” PAC glaucoma may sometimes lead to brief subjective symptoms in the form of rainbow haloes and blurred vision.

As mentioned in III B, C and D, post-YAG laser assessment (gonioscopy and LCD) should be carried out as soon as possible after iridotomy with regard to performing iridoplasty in order to avoid plateau iris conditioned acute angle closure. In all cases it is important to assess whether the drug treatment is adequate (diurnal curve). In plateau iris dominance requiring iridoplasty, the required drug treatment often includes pilocarpine as mentioned in II E (p. 80). In case of doubt, a prone dark-room test on drug treatment excluding pilocarpine may be carried out.

F

As in the corresponding groups under I and II, structural changes to the optic nerve head and in the retinal nerve fibre layer with associated visual field defects are found in manifest PAC glaucoma (glaucoma angulo clauso) mixed group. The pressure is permanently increased (≥ 24 mmHg) due to PAS in more than 80-90 degrees of the angle circumference.

When identification of PAS in 360 degrees of the circumference can be verified with a reasonable degree of certainty, a pressure reducing effect of YAG-laser iridotomy/argon-laser iridoplasty or indeed cataract operation is not to be expected. In such a situation, maximum drug treatment (three different medications at most) is prescribed, naturally including pilocarpine. This decision is supported by diagnosing the presence of severe structural changes (C/D ratio: 0.8 or 0.9) and/or extensive functional defects. In case of suspect terminal PAC glaucoma an adequate ophthalmoscopy, if necessary after pupil dilation with metaoxedrine 2,5% drops, and a subsequent automatic perimetry is therefore recommended

90 Main groups and subclassification of PAC

Case report 7

Chronic PAC mixed group with plateau iris dominance

(see fig. 23, UBM from this patient)

A 44-year-old nurse with a history of 5-10 attacks of blurred vision and rainbow haloes in both eyes every year for the last four years. A severe attack with nausea, blurred vision and rainbow haloes four weeks prior to ophthalmic consultation.

Diagnosis given

by the referring ophthalmological department: 1. Bilateral intermittent primary angle-closure glaucoma.

Bilateral LCD < 0.25, ACD 2.0/2.2 mm, gonioscopy showed narrow occludable angles with PAS in the upper sector in both eyes, Goldmann applanation: 20/18 mmHg on treatment with pilocarpine 4 % (local ophthalmologist) and normal optic discs without structural changes.

Discharged to the local ophthalmologist the day following therapy, but without gonioscopy and without treatment as the patient is informed that “the problem is most likely solved”.

2. Plateau iris glaucoma

Again referred by the local ophthalmologist after two weeks following an attack with rainbow haloes in the right eye. Goldmann applanation 16 mmHg in both eyes on treatment with pilocarpine.

Due to a suspicion of a subclinical attack: Dark-room test without pilocarpine (19/18 mmHg → 57/34 mmHg + rainbow haloes).

Treatment:

After this dark-room test: Pilocarpine treatment for six months with considerable miosis discomfort (blurred vision a few hours after pilocarpine. The patient managed by not wearing glasses after the pilocarpine application). Due to the discomfort referral to the glaucoma clinic.

Bilateral LCD = 0.25, ACD 2.2/2.3 mm, large iridotomies and narrow, occludable angles with plateau iris configuration and little iris mobility on gonioscopy. PAS 10-3 o’clock in the right eye, 12-3 o’clock in the left eye as is illustrated in fig. 23 (UBM from the patient), bilateral C/D ratio 0.2 without structural changes and normal visual fields on automatic perimetry.

Treatment: Iridoplasty x 2 on both eyes.

After this, dark-room test without pilocarpine was negative (17/15 → 19/17 mmHg). The course was then satisfactory with IOP < 20 mmHg without treatment with an observation time of four years. Due to suspicion of continuing PAS development, renewed bilateral iridoplasty after three years.

Main groups and subclassification of PAC 91

Comments

Reason for unspecific treatment:

1.Lack of pre-laser main classification of PAC owing to insu cient gonioscopy (no plateau iris configuration or iris mobility assessment with the Posner lens) and lack of interpretation of the ACD measurement.

2.Consequently, the required gonioscopy immediately after YAG-laser iridotomy was not carried out.

3.No application of argon-laser iridoplasty.

Outcome of unspecific treatment:

1.Patient frustration due to renewed referral with recurring glaucoma attack in spite of “curative” YAG-laser iridotomy.

2.Visual problems caused by pilocarpine treatment.

before treatment. Case report 8 is an example of unspecific treatment of manifest PAC glaucoma due to inadequate gonioscopy and insufficient assessment of structural/functional defects and illustrates the consequences that ensued.

If in doubt as to the stage of development of PAC, an iridotomy possibly followed by iridoplasty can be performed, but this may lead to post-laser pressure increases, especially in advanced glaucoma. In terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) YAG-laser iridotomy and argon-laser iridoplasty are therefore generally contraindicated.

If maximum drug treatment is not accepted or when a diurnal curve shows a peak pressure of > 20 mmHg, a filtrating operation should be carried out, possibly a combined cataract trabeculectomy procedure (ref: Treatment procedures: Fistulating operation, p. 108).

YAG-laser iridotomy/argon-laser iridoplasty: Evaluation

The indication for YAG-laser iridotomy and argon-laser iridoplasty in the mixed group is the same as described in the section concerning iridotomy evaluation under I. PAC with pupil block (p. 67) and the section concerning iridoplasty evaluation under II. PAC with plateau iris (p. 80). As mentioned above, these laser indications also apply to imminent PAC in the mixed group. The advantage of the correct classification of an eye into the mixed group is that it not only creates the possibility for proper planning of treatment, but also allows realistic patient information to be given with regard to the expected treatment course. With regard to subsequent iridoplasty, the indication for this should be estab-

Main groups and subclassification of PAC 93

Comments

Reason for unspecific treatment:

1.The local ophthalmological department did not carry out an ACD measurement or establish a PAS diagnosis owing to inadequate gonioscopy (Posner indentation was not performed).

2.Incorrect optic nerve head assessment (normal discs). Incorrect suspicion of plateau iris, because iris motility was not assessed.

3.No final diurnal curve was performed with regard to adequacy of treatment.

Outcome of unspecific treatment:

1.The patient was discharged from the ophthalmological department without drug treatment after YAG-laser iridotomy. This led to a new acute referral.

2.This new acute referral led to unspecific submaximal drug treatment instead of optimal treatment due to inadequate PAC subclassification in the right eye.

lished as soon as possible after performing iridotomy, i.e. preferably on the following day by means of gonioscopy without the use of pilocarpine and under minimum illumination (both lighting in the room and slit lamp). In case of doubt a prone dark-room test is recommended.

YAG-laser iridotomy/argon-laser iridoplasty in general

See the same section under groups I and II (p. 69 and 83).

94 Main groups and subclassification of PAC