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TREATMENT PROCEDURES WITH PAC

By John Thygesen

PRINCIPLES OF TREATMENT WITH ACUTE PAC I, II AND III

•Examine both eyes and make note of both peripheral and central chamber depths (LCD and ACD), the contour of the iris as well as the findings on indentation gonioscopy. Should corneal oedema preclude adequate examination of the acute eye, base the initial PAC diagnosis on the examination of the fellow eye.

•Lower intraocular pressure using drugs that reduce the production of aqueous fluid: Carbonic anhydrase inhibitors, beta-blockers and alfa2-agonists.

•Repeat the ophthalmological examination after 1/2-1 hour. The IOP will typically be reduced, but the angle will remain appositionally closed. At a tension < 50 mmHg the pressure conditioned ischaemia will typically have subsided and the pupillary sphincter therefore be sensitive to pilocarpine medication. One drop of pilocarpine 2% should then be administered and assessment repeated after a further 15-30 minutes. If necessary repeat the pilocarpine treatment 3-4 times during the following hour.

•If after the first 1/2-1 hour the pressure remains > 50 mmHg, oral hyperosmotic agents such as glycerol or intravenous mannitol (cave diabetes, pulmonary oedema) may be added followed by pilocarpine.

•Procedure in connection with hyperosmotic agents: Place the patient in a supine position. This allows the lens to gradually fall back into position as the volume of the vitreous body becomes reduced by the hyperosmotic agents used. This reduction comprises only about 3% of the total vitreous volume, but this is equivalent to 0.12 cc or twice the volume of the posterior chamber or half of the volume of the anterior chamber.

•If the pressure is thereby reduced and a repeated gonioscopy in the acute eye (typically after applying 50% glucose in order to remove any remaining corneal oedema) shows a narrow occlud-

96 Treatment procedures with PAC

able angle without PAS, pilocarpine 2% x 4 daily is prescribed together with local steroids until the inflammation has been further reduced.

•Based on gonioscopy (ref: 1. Iris contour and iris mobility, p. 33) together with ACD measurement the case in question is classified under I, II or III (ref: Main classification of PAC, p. 50), whereas the subclassification with the attached final specific treatment are based on the presence of any PAS, any structural optic disc changes, and/or functional defects (ref: Subclassification with specific treatment, PAC groups I, II and III, p.58, 75 and 85).

•As mentioned under latent and manifest PAC glaucoma groups I, II and III, an asymptomatic “creeping” chronic PAC may sometimes become converted into a subacute/acute condition, i.e. behind a seemingly acute PAC, a chronic condition in the need of post-laser medical therapy or even a fistulating operation may be hidden. Therefore, as repeatedly mentioned in the foregoing chapters, a thorough initial examination before starting any treatment is of vital importance in order to avoid unspecific treatment (“trial and error” method).

N.B.! The axiom to date in angle-closure glaucoma has been to use extensive amounts of pilocarpine. However, this is only very seldom necessary. Should excess therapy with pilocarpine 4% be applied, a rise in pressure due to an increased pupil block may sometimes paradoxically occur and gastrointestinal side effects may present.

TREATMENT OF ACUTE PAC I, II AND III (PREVIOUSLY “ACUTE GLAUCOMA”)

I. Preliminary treatment

1. Reduction of aqueous fluid production

Acetazolamide (Diamox®) 10 mg/kg intravenously (cave sulphonamide allergy) (N.B.! Topical CAIs such as dorzolamide (Trusopt®) or brinzolamide (Azopt®) are not recommended as they have a reduced IOP lowering effect in the presence of corneal oedema). Local alpha -agonist (e.g.: Iopidine®, Alphagan®).

2

Local betablockers (cave asthma).

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2.Elimination of iris/cornea apposition (restitution of outflow)

Corneal indentation with a hand-held Goldmann tonometer head. Aqueous fluid in the anterior chamber is thereby pressed into the chamber angle, which may then be opened in certain cases.

3.Pupil constriction

Pilocarpine eye drops 2% x 1, 1/2-1 hour after performing points 1 and 2 as IOP is then generally < 50 mmHg, i.e. the pupillary sphincter is again pilocarpine sensitive due to the elimination of the pressure conditioned ischaemia. The pilocarpine 2% medication is repeated 3-4 times during the following hour. (Stronger miotics such as pilocarpine 4% or more frequent doses may sometimes increase the pupil block and lead to a so-called paradoxical pressure increase.)

4. Inflammatory treatment

Local corticosteroid, e.g. dexamethasone x 4 daily.

II. FOLLOW-UP TREATMENT AFTER 1-2 HOURS

A. If the attack is interrupted: Pressure reduced. Pupil contracted. Corneal oedema reduced.

1. Classification

Repeat the gonioscopy and possibly the ACD with regard to a final classification into main groups and subgroups with regard to the specific treatment of the case in question.

2. Pupil constriction

Prescribe pilocarpine eye drops 2% x 4 daily for both eyes. In the presence of extensive PAS possibly combined with structural optic disc changes further drug treatment should be administered as mentioned in the chapters: Subclassification and specific treatment of PAC I, II and III (p. 58, 75 and 85).

3. Inflammatory treatment

Local corticosteroid, e.g. dexamethasone x 4 daily.

4. YAG-iridotomy and argon-laser iridoplasty

An iridotomy should be arranged for in both eyes in acute PAC with pupil block (I) and in the mixed group (III) when the pupil block appears to be the dominating factor (ref: Acute PAC, group I,

98 Treatment procedures with PAC

p. 59 and III, p. 87). In acute PAC with plateau iris, arrange for a primary iridoplasty (ref: II: Acute PAC with plateau iris, p. 77).

Should the final classification indicate subacute/acute attack in a previous asympomatic, chronic course, the specific treatment of the case concerned is planned as illustrated in the chapters: Subclassification with specific treatment of PAC groups I, II and III.

YAG-laser iridotomy and argon-laser iridoplasty:

Generally, preventive iridotomy should first be performed in the healthy eye. Iridotomy in the acute eye should not be carried out until the cornea has cleared and the intraocular inflammation has been sufficiently reduced (iris without hyperaemia). In the case of uncertain gonioscopic subclassification it is important to note that a reduced IOP in the days immediately following acute PAC may be caused by a reduced aqueous production due to pres- sure-conditioned ciliary body ischaemia. In other words, the pressure reduction itself cannot alone account for any opening of the chamber angle. In such cases, observation on the above-mentioned medication will clarify the situation making it possible to avoid unspecific treatment. Generally, however, iridotomy should be carried out as soon as technically possible in order to utilize the synecholysis effect of the treatment on any new PAS formations. Adequate gonioscopic evaluation should therefore be carried out as early as possible in the course of the disease process with regard to the optimal planning of the specific treatment.

In iridoplasty in acute PAC with plateau iris (II) the same considerations as mentioned above are applicable. It is to be noted that direct argon-laser iridoplasty using an Abraham lens (really designed for iridotomy) can adequately be carried out in the presence of a slightly cloudy cornea, i.e. earlier than iridotomy (see below).

B: If the attack is not interrupted: Pressure continuously high. Pupil dilated. Cornea oedematous.

1. Osmotic reduction of the vitreous volume

Oral Glycerol 1.0-1.5 g/kg (cave diabetes) or intravenous 20% Mannitol (1.0-1.5 g/kg) over 30 minutes.

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2. Supine position for one hour

In this manner the lens will gradually move posteriorly as mentioned above.

3.If the patient is in pain: Systematic analgesics.

4.If the patient feels nauseous or is vomiting: Intramuscular metoclopramide.

C: If the attack is then interrupted

1.Continue pilocarpine eye drops 2% x 4 daily.

2.Continue corticosteroid eye drops x 4 daily.

3.Plan specific treatment as mentioned under A.

D: If the attack is not successfully interrupted, i.e. IOP > approx. 30 mmHg

With a clear cornea:

Repeated gonioscopy with regard to final subclassification as a continued increased IOP in spite of clear cornea generally implies PAC glaucoma in group I, II or III.

Following this, specific treatment is planned as illustrated in fig. 19, p. 52: Flow chart for specific treatment of PAC.

In the presence of visually impairing cataract, phaco-extraction may improve the outflow possibilities in latent PAC glaucoma. An improved outflow should not of course be expected in manifest PAC glaucoma where PAS involves almost the entire circumference (> 80-90%), indeed in this situation there is a risk of a post-opera- tive increase in pressure. In such a case a combined cataract and glaucoma operation should therefore be considered (ref: Fistulating operation).

With continued cornea oedema:

If it is not possible to carry out adequate gonioscopic subclassification and YAG-laser iridotomy, and when the patient history indicates a short-term acute course, argon-laser iridoplasty should be attempted even though examination of the healthy eye suggests that the case belongs to groups I, or III.

100 Treatment procedures with PAC

With continued extreme cornea oedema:

If it is not technically possible to perform an iridoplasty, the case is treated as in manifest PAC glaucoma (ref: Flow chart, fig. 19, p. 52).If maximum drug treatment including pilocarpine does not lead to IOP ≤ 20 mmHg, or if the patient is unable to accept the treatment, a fistulating operation should be performed.

As the situation is often caused by PAS in the entire angle circumference, a cataract extraction will naturally not improve the outflow situation.

YAG-LASER IRIDOTOMY

YAG-laser iridotomy eliminates the pressure difference between the anterior and posterior chambers caused by the abnormal pupil block and thereby flattens the iris. In this way, the chamber angle is opened provided there are no PAS present (see also: Pathophysiology and pathogenesis, Group I: PAC with pupil block, p. 53).

Indications

•Imminent PAC with pupil block groups I and III

•Acute/subacute PAC with pupil block groups I and III

•Chronic PAC with pupil block groups I and III

•Latent PAC glaucoma with pupil block groups I and III (In manifest PAC glaucoma with pupil block (I) and mixed group (III) where PAS are present in > 80-90% of the angle circumference iridotomy will not have a pressure reducing effect, possibly even the opposite) Concerning YAG-laser indications and necessary post-laser anti-glaucomatous drug treatment see also: Subclassification with specific treatment of PAC with pupil block group I, p. 58) and group III (p. 85) as well as fig. 19 (p. 52): Flow chart for specific treatment of PAC

Contraindications

•Terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision) with pupil block groups I and III due to the risk of post-laser increase in pressure

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•Extremely flat anterior chamber with iris/cornea contact as is for instance found in nanophthalmos (ref: Pathophysiology and pathogenesis, PAC with pupil block, p. 55). Under such circumstances iridotomy may result in ciliary block or uveal effusion (formerly known as malignant glaucoma). The alternative laser treatment is iridoplasty

•Pronounced corneal oedema

•Anticoagulation therapy and acetylsalicylic acid treatment: The treatment should be interrupted for a few weeks prior to laser application

Technique26

•Local anaesthesia

•Apraclonidine (Iopidine®) pre-laser: Reduces post-laser pressure increase and bleeding

•2% pilocarpine x 1 pre-operatively in order to achieve miosis and thus an extension of the iris tissue (easier laser perforation) and an improved possibility for creating a peripheral iridotomy, which will be covered by upper eyelid (no dazzle)

•Lens: Wise laser-iridotomy lens (ocular + 103 D)

•Laser burns:

Energy:

Start with 1.5 – 3.0 mJ.Adjust for iris colour. Energy in brown iris > blue iris.

In brown iris: Defocus posteriorly towards the iris pigment layer (“volcano effect” with maximum energy absorption in the pigment layer).

Preferably no more than five applications

Choose an iris crypt peripherally in the upper area where the patient’s eyelid will provide cover (fig. 26). In this manner, dazzle and lens damage may as mentioned be avoided.

Register the functional iridotomy effect by observing the change in LCD. If there is no change in the limbal chamber depth: Assess whether the iridotomy has penetrated all iris tissue and whether it is large enough (ref: YAG-laser iridotomy in general, p. 69).

Possibly repeat the gonioscopy with regard to reviewing the classification (PAS?).

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Fig. 26. Combined YAG-laser iridotomy/argon-laser iridoplasty in a patient with imminent PAC III, mixed group with plateau iris dominance. Svend V. Kessing, the Glaucoma Clinic, Copenhagen University Hospital.

•Post-treatment:

Local steroid x 3-4 daily for 3-5 days

•Control:

Pressure measurement after 1-3 days.

Especially in cases with PAC mixed group (group III), gonioscopy should be repeated the following day with regard to possible plateau iris with continued occludable angle representing an indication for iridoplasty

•Complications: Haemorrhage from iris.

IOP increase (within 3 hours post-laser). Minor iritis and posterior synechiae. Closure of iridotomy.

Lens damage? Corneal laser marks

See also: YAG-laser iridotomy: Evaluation (p. 67).

ARGON-LASER IRIDOPLASTY

In argon-laser iridoplasty8 laser energy is applied centrally to the pathological prominent iris knee (ref: Normal anatomy of

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the chamber angle, 1. Iris contour and iris mobility (p. 33) and pathophysiology and pathogenesis, group II, PAC with plateau iris, p. 71). The heat generated causes shrinkage of the iris tissue, thus opening the narrow chamber angle (fig. 27). In group II: PAC with plateau iris where the pathogenesis is purely plateau conditioned without any pupil block component, iridoplasty represents the specific treatment since YAG-iridotomy does not have any effect whatsoever in this situation (see case report 4, p. 79).

Fig. 27. Argon-laser iridoplasty in plateau conditioned PAC.

Indications

•Imminent (threatening) PAC with plateau iris (group II) and imminent PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle.

•Subacute/acute PAC with plateau iris (group II) and subacute/ acute PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle.

•Chronic PAC with plateau iris (group II) and chronic PAC mixed group (group III) in cases where YAG-laser iridotomy in group III has not opened the chamber angle.

•Latent PAC glaucoma with plateau iris (group II) and latent PAC glaucoma, mixed group (group III) in cases where YAGlaser iridotomy has not opened the chamber angle.

•(In manifest PAC glaucoma with plateau iris (group II) or mixed group (group III) with PAS in > 80-90% of the angle circum-

104 Treatment procedures with PAC

ference iridoplasty most often will have no pressure reducing effect, possibly even the opposite.)

•With regard to iridoplasty indications and possible post-laser anti-glaucomatous drug treatment see also: Subclassification with specific treatment, groups II and III (p. 75 and 85) and fig. 19: Flow chart for specific treatment (p. 52).

Relative iridoplasty indications

•Subacute/acute PAC with pupil block where acute anti-glau- comatous drug treatment is ineffective and where there is no possibility of obtaining a sufficient YAG-laser iridotomy owing to cornea oedema

•Secondary angle-closure (SAC) due to a subluxated lens (for- ward-axial) and in hypermature cataract with increasing lens thickness where the YAG iridotomy is inadequate

•Nanophthalmos (ref: Group I: Pathophysiology and pathogenesis, p. 56) as an alternative to YAG-laser iridotomy

Contraindications

•Pronounced corneal oedema (may lead to corneal burns in both endothelium and stroma)

•Flat anterior chamber with extensive iridocorneal contact (in some cases laser treatment may be initiated intermedially on the iris and then followed up by placing the burns in a more peripheral fashion resulting in successive peripheral angle opening, e.g. in nanophthalmos)

•Terminal manifest PAC glaucoma (C/D ratio 0.9 and/or tunnel vision).

Technique

•Local anaesthesia

•Apraclonidine (Iopidine®) pre-operatively

•2% pilocarpine x 1 pre-operatively in order to pull the iris knee as centrally as possible (should not be used following iridoplasty)

•Laser wavelength: Blue-green

•Lens: Abraham iridotomy lens (ocular + 66 D), which provides a suitable enlargement whereas the Wise iridotomy lens (ocu-

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lar + 103 D) provides an enlargement, which is excessive and therefore impractical (see also: Argon-laser iridoplasty in general, group II, p. 83)

•Laser burns:

*24 burns placed over 360 degrees with approx. 2 “spot” diameters between each burn (fig. 26 and 27). Focus peripherally

on the iris (on the iris knee).

Highest energy in lesser pigmented irises. Determine the required energy amount (immediate visible iris shrinkage) in each individual patient by “titration”, always starting with a low energy position (100 mW).

In case of bubble formation: Reduce the energy

•Post-treatment:

Local steroids x 3-4 daily for 3-5 days

•Control:

Gonioscopy immediately post-laser and then at least annually in order to assess any degree of angle closure requiring further iridoplasty treatment (Ref: Group II, Argon-laser iridoplasty: Evaluation p.69.)

•Complications: Minor iritis. Larger pupil.

Iris pigment hypertrophy from the laser burns. Rarely increase in IOP

FISTULATING OPERATION

By Svend V. Kessing

It is not the aim of this book to give a detailed account of the trabeculectomy procedure as such. However, indications and postoperative treatment will be mentioned together with a brief description of the post-operative complications, which are especially found to occur in PAC with pupil block. Finally, suggestions for preventive measures in connection with these complications will be put forward.

106 Treatment procedures with PAC

Indication

Primarily in manifest PAC glaucoma with pupil block (group I), with plateau iris (group II) and mixed group (group III) when maximum anti-glaucomatous medication is ineffective (ref: Subclassification with specific treatment of PAC I, II and III, p. 58, 75 and 85; and fig. 19, p. 52: Flow chart for specific treatment).

In the case of terminal manifest PAC glaucoma in an only eye, transscleral diode laser cyclophotocoagulation should be considered instead of trabeculectomy due to the complications which can occur in fistulating operations as mentioned below.

Complications

1. Post-operative hyperfistulation

Due to the particular pathoanatomy found in eyes with PAC with pupil block (ref: Pathophysiology and pathogenesis, group I PAC with pupil block, p. 55), there is a pronounced tendency for postoperative hyperfistulation to occur as compared to eyes with primary open-angle glaucoma. This leads to hypotension with various degrees of anterior chamber flattening.

2. Choroidal detachment

Hypotension often leads to choroidal detachment with further hypotension due to the cessation in aqueous production that follows. This will result in a closure of the filtrating bleb (subconjunctival fibrosis) and an increased IOP when aqueous production is re-es- tablished, i.e. indication for re-operation.

3. Ciliary block (formerly known as malignant glaucoma)

This complication is almost only found in manifest PAC glaucoma since it is only very seldom seen in either primary or secondary open-angle glaucoma.

As is well-recognised, this is a most serious complication that requires urgent acute operative intervention with “vitreous tap” (removal of intravitreal aqueous pockets), most easily done via an opened trabeculectomy, which is subsequently closed in a more solid fashion. In the situation with a large iridectomy YAG laser photo-disruption of a visible hyaloid membrane could be attempted before performing a “vitreous tap”.

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Prevention of post-operative hyperfistulation

The above-mentioned hyperfistulation is prevented by using 6 tight 10-0 nylon sutures in the scleral flap where the two most limbal sutures are placed as so-called disposable sutures, i.e. sutures where the knots are situated in the cornea enabling them to be removed without any risk of external fistulation. This procedure is preferred to post-operative transconjunctival laser-burning of the sutures, which in fact is often quite impossible to perform due to conjunctival oedema and haemorrhage.

This suture technique is especially necessary when using 5-FU or Mitomycin C for anti-fibrotic treatment as these treatment procedures alone involve a high risk of hyperfistulation.

In this connection, it should be emphasised that a combined cataract and glaucoma operation requires anti-fibrotic treatment in order to ensure continued fistulation. In a combined operation separate procedures are therefore recommended with a corneal phacoextraction and a separate trabeculectomy with Mitomycin C (0.2 mg/ml for 3 minutes) in the upper area of the eye.

In cases of terminal PAC glaucoma, trabeculectomy alone is recommended followed by phacoextraction through a corneal incision as combined operations have higher post-operative pressure levels than a solitary trabeculectomy.

Post-operative treatment

1.Scopolamine eye drops x 3 daily for as long as hypotension (IOP < 5 mmHg) and a tendency towards flat anterior chamber exist.

2.Steroid eye drops, e.g. dexamethasone x 4 daily, individualised (> 5 weeks) until a non-hyperaemic, diffuse fistulation bleb is found (i.e. no sign of active subconjunctival fibrosis).

3.Cutting of disposable sutures (anteriorly placed scleral flap sutures as mentioned above) when IOP is > 15 mmHg. With adequately tightened scleral flap sutures in cases without antifibrotic treatment (5 FU or Mitomycin C) it is generally advisable to cut the disposable sutures on the second or third post-operative

108 Treatment procedures with PAC

day. When anti-fibrotic treatment has been used, suture cutting should be left until at least one month post-operatively.

4.Bulbar massage to create “hydro-dissection” of incipient subconjunctival fibrosis (in cystic blebs). Bulbar massage is carried out under slit lamp control using gentle and continuous pressure at the outer angle of the eyelid with the index finger, thereby compressing the bulbus against the nasal orbital wall. At the same time, the bleb is observed through the slit lamp enabling finger pressure to be adjusted according to changes in the bleb appearance. With a high bleb configuration without any spreading to the conjunctiva on the sides bleb compression is carried out transpalpebrally (“bleb modulation”) in order to hydro-dissect any tendency to subconjunctival fibrosis until the bleb has become more diffuse.

It should be emphasised that the primary purpose of bulbus massage is to eliminate incipient subconjunctival fibrosis and not to reduce the eye pressure. Bulbus massage should therefore be carried out as soon as IOP > approx. 10 mmHg and not left until the pressure has become increased (> 20 mmHg) as the fibrosis will generally be irreversible at this stage.