Ординатура / Офтальмология / Английские материалы / Atlas of Glaucoma, Second Edition_Choplin, Lundy_2007

Figure 1.2 Rieger’s syndrome. This eye shows many of the structural abnormalities of anterior segment dysgenesis affecting the iris, cornea, anterior chamber angle, and pupil. See Chapter 14 for a complete discussion of this syndrome and other developmental glaucomas.

of findings (Chapter 8). At one extreme is the mild diffuse loss of early POAG while the patient with advanced normal tension glaucoma (NTG) may demonstrate focal defects which are deep and close to fixation (Chapter 12). Evidence of structural damage to the optic nerve or dysfunction of the retinal nerve fibers will usually precede the functional damage seen in the visual field, and may sometimes be detectable by newer diagnostic modalities (Chapter 7).

Befitting such a diverse group of diseases, treatment of the glaucomas ranges from careful observation in some patients with ocular hypertension (Chapter 9) to cyclodestructive surgery and tube shunts (Chapter 19) for neovascular glaucoma. Medical therapy (Chapter 15), the mainstay of treatment for most types of glaucoma at this time, ranges from topical prostaglandin analogues in POAG to oral calcium channel blockers in NTG to intravenous carbonic anhydrase inhibitors in acute angle closure. Laser surgery (Chapter 16) may be offered to the glaucoma patient: laser peripheral iridotomy (LPI) for primary angle closure glaucoma, laser trabeculoplasty for exfoliation glaucoma, iridoplasty for plateau iris, or ciliary body destruction as an end-stage procedure in all types of glaucoma. Surgery may be the primary treatment modality as in goniotomy for congenital glaucoma (Chapter 21), or an end-stage procedure as in enucleation for the patient with a blind painful eye as the result of a central retinal vein occlusion and recalcitrant neovascular glaucoma. More often, surgery such as a trabeculectomy or a tube shunt is offered after medical and laser treatment fail to adequately control progression of optic nerve damage (Chapters 17–20).

In spite of the broad range of treatment modalities available, the prognosis of the glaucomas is variable and reflects the broad scope of underlying etiologies. The typical myopic male patient with onset of pigment dispersion glaucoma in his forties

has a much better prognosis than the patient with absolute glaucoma as the result of an ischemic central retinal vein occlusion and complete angle closure from iris neovascularization. POAG is the most common type of glaucoma and has a fairly good prognosis in most cases once the diagnosis is made. However, delay in diagnosis can lead to blindness or significant visual disability. The risk of functional visual loss is of even greater concern, given the ever lengthening average life expectancy of our patients.

The diagnosis of glaucoma may be difficult to make, particularly on a single examination. Considering the progressive nature of the disease, observation of its progression may be necessary to confirm the diagnosis. Consider the patient whose photograph of the right optic disc is shown in Figure 1.3a. This patient is an African-American male in his mid-fifties with elevated intraocular pressure (midtwenties) in both eyes. His visual field examination was entirely within normal limits, and the other eye was identical, i.e. symmetrical. He was started on medical therapy to lower his pressure, and followed at regular intervals. Figures 1.3b and c are disc photographs of the same eye taken 7 and 9 years later, respectively. Each time the visual field remained normal, although there was a very subtle but steady decrease in mean sensitivity. The optic discs remained symmetrical. Taken as a series, these photographs demonstrate concentric enlargement of the cup over time, corresponding to the diffuse loss of sensitivity in the visual field. Each individual time period, viewed independently of the rest, is consistent with ‘ocular hypertension’ and might be treated by periodic follow-up visits, as with this patient. Viewed as a series, however, this patient clearly has progressive open-angle glaucoma. Glaucoma, therefore, may be like a movie depicting the destruction of the optic nerve, with each examination but one frame from the movie.

Further difficulty in making a diagnosis arises when the patient’s examination is seemingly normal. The photograph in Figure 1.4a was obtained because the fellow eye had a congenital optic nerve pit. Additional photographs were obtained when the patient developed giant cell arteritis (biopsy proven), but without any evidence of acute anterior ischemic optic neuropathy. Figures 1.4b–d were obtained 6, 7 and 8 years after Figure 1.4a, respectively. There is a steady concentric enlargement of the cup, with extension inferiorly, eventually reaching the inferior disc rim. Intraocular pressure in this eye was never greater than 18 mmHg. This would most likely be termed ‘normal tension glaucoma’, and in this case may be due to chronic ischemia. Again, it is the observed progression over time that leads to the diagnosis, not the individual examinations.

Observation of progression is really the key to diagnosing the optic nerve disease of glaucoma.

(c)

There are hundreds of optic nerve diseases, many of which comprise a single event leading to damage and never progress or change over the remainder of the patient’s lifetime. A good example would be non-arteritic anterior ischemic optic neuropathy. It thus becomes the important but often difficult task to identify those who truly have disease as early as possible to prevent loss of visual function, while avoiding treatment in those who do not need it.

Glaucoma has to start at some point in a person’s life. The progression of the disease from ‘normal’ to axonal dysfunction to death of axons to visual dysfunction to blindness has been termed by Dr Robert Weinreb from the University of California in San Diego the ‘glaucoma continuum’ and is illustrated in Figure 1.5. The concept of glaucoma as a disease characterized by progressive loss of retinal nerve fibers at a rate greater than expected for age, along with the rationale for ‘early’ diagnosis and institution of therapy, is illustrated in Figure 1.6.

RISK FACTORS FOR

GLAUCOMATOUS DISEASE

One could debate what the concept of ‘glaucoma treatment’ actually means. All current treatment for glaucoma consists of lowering intraocular pressure.

But, in reality, glaucoma is a disease of the optic nerve and retinal nerve fiber layer. Lowering intraocular pressure reduces the risk of glaucoma developing (in the case of ocular hypertension) or progressing (in the case of established open angle glaucoma) (Table 1.1). Therefore, until we can repair the damage to the optic nerve, we are really treating risk. A useful summary of risk evaluation as determined from a host of recent clinical trials was presented by Dr Graham Trope from Canada at the International Glaucoma Symposium held in Cape Town, South Africa in March of 2005, and is shown in Table 1.2.

POAG is the most common of the glaucomas and affects an estimated two million Americans, half of whom are unaware that they have the disease. Since it is often asymptomatic in the early to moderately advanced stages, patients may suffer substantial irreversible vision loss prior to diagnosis and treatment. Therefore, considerable effort has been made to identify at-risk populations and develop accurate screening tests to make the diagnosis in order that sight-preserving treatment can begin early in the disease process. Several populationbased studies have been carried out to determine the prevalence of POAG as well as identifying risk factors for the disease (Chapter 9). Some of the information from these studies is conflicting, but

race and intraocular pressure consistently appear as risk factors. In one US urban population, the ageadjusted prevalence of POAG was four times greater for African-Americans as opposed to Caucasians. Elevated intraocular pressure ( 22 mmHg) was also associated with a greater incidence of glaucoma. However, in this same group, 16% of persons with glaucomatous nerve changes and field loss never had an intraocular pressure greater than 20 mmHg on multiple examinations. Unfortunately, intraocular pressure, while easy to measure in a massscreening setting, is a much poorer predictor of disease than visual field or optic nerve examination. Visual fields and dilated optic nerve examinations, while more sensitive and specific, are time and labor intensive, and therefore not conducive to screening large numbers of people. Newer methods of optic nerve examination, which can be performed rapidly through the non-dilated pupil, may offer better means of screening for POAG (Chapter 7).

Myopia, systemic hypertension, diabetes mellitus, or a family history of glaucoma have long been associated with an increased risk for POAG, although results of recent studies have questioned the strength of these associations. Many still consider these as risk factors, although to a lesser degree than race and elevated intraocular pressure. There may also be an association between angle-recession (post-traumatic) glaucoma and POAG in the non-recession eye as well as central vein occlusion (CRVO) and POAG in the non-CRVO eye. In addition, there is good evidence that patients who demonstrate steroid responsiveness (elevated intraocular pressure with chronic steroid use) have a higher incidence of POAG than non-responders. Identifying pertinent risk factors and accurate screening criteria for glaucoma are complex issues complicated by the fact that we are dealing with a heterogeneous collection of diseases rather than a single entity. However, the asymptomatic nature of the majority

Percentage of functional

axons remaining

of glaucomas and the irreversible nature of the resulting vision loss demand effective screening strategies if we are to make early vision-preserving interventions.

Glaucoma thus comprises a group of diseases encompassing a broad spectrum of clinical presentations, etiologies, and treatment modalities. The pathophysiology of the glaucomas remains

uncertain and research efforts are hindered by the fact that we are dealing with a heterogeneous group of diseases rather than a single entity, but one that results in a common end point. However, as we learn more about the differing routes to their common end point, we hope to be better able to classify and treat this group of vision-threatening diseases.

Gordon MO, Beiser JA, Brandt JD, et al., for the Ocular Hypertension Treatment Study Group. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open angle glaucoma. Arch Ophthalmol 2002; 120: 714–20

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Klein BEK, Klein R, Sponsel WE, et al. Prevalence of glaucoma: the Beaver Dam Eye Study. Ophthalmology 1992; 99: 1499–504

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West Indies. Ophthalmology 1989; 96: 1363–8

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Tielsch JM, Katz J, Singh K, et al. A population-based evaluation of glaucoma screening: the Baltimore Eye Survey. Am J Epidemiol 1991; 134: 1102–10

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INTRODUCTION

As discussed in Chapter 1, the term ‘glaucoma’ encompasses a wide variety of diseases and conditions. In order to arrive at a working diagnosis and institute appropriate therapy, the patient’s history must be obtained and an examination performed. Classification of diseases such as glaucoma into various categories, each distinguished from the other by some essential characteristic or set of characteristics, allows us to deal with a patient’s disease appropriately. For example, the initial treatment of a patient with a pressure of 48 mmHg due to angleclosure glaucoma is very different from that of a patient with the same pressure presenting for the first time with open-angle glaucoma. Similarly, the therapeutic goal set for a patient with extensive visual field loss and optic nerve cupping may be very different if the presenting intraocular pressure was 40 as opposed to 21. Thus, the approach to diagnosis often looks along some sort of classification scheme in which the subcategories have common diagnostic or therapeutic characteristics. Various classification schemes exist, and almost all glaucomatous disease falls somewhere in all of them. Most of the entities will be discussed in other chapters of this atlas.

CLASSIFICATION OF GLAUCOMA BY MECHANISM

The mechanistic classification is probably the most common scheme for sorting out the various glaucomatous diseases (Figure 2.1). The main division of this classification is between open-angle and angleclosure glaucoma. This type of division emphasizes the importance of gonioscopy (Chapter 5) for arriving at the correct diagnosis. It would be impossible to differentiate between primary open-angle glaucoma

and primary chronic angle-closure glaucoma (where the patient never had an acute attack) without gonioscopy. The other important differentiation in this classification scheme is between primary (primary disease of the eye with no associated conditions or diseases) and secondary glaucomas (where the glaucoma is attributed to some underlying condition or disorder). This differentiation may be important for therapeutic considerations. For example, primary open-angle glaucoma may respond well to miotics such as pilocarpine while inflammatory glaucoma may be worsened by treatment with miotics. Iridotomy is appropriate for treating pupillary block angle closures, but not non-pupillary block angle closure. Note that the classification scheme as presented here does not mention ‘narrow angle’ glaucoma. The term ‘angle closure’ is preferred, since ‘narrowing’ of the anterior chamber angle is really of no significance until the angle becomes closed (partially or completely).

CLASSIFICATION BY AGE OF ONSET

Table 2.1 illustrates a classification of glaucoma by age of onset. The developmental glaucomas are discussed in Chapter 14.

CLASSIFICATION BY INTRAOCULAR PRESSURE

The main subdivisions in this classification are ‘hyperbaric’ and ‘normal or low tension’ glaucoma. Table 2.2 lists some distinguishing characteristics. The term ‘hyperbaric’ is not often used except to distinguish ‘garden variety’ open-angle glaucoma from normal-tension glaucoma. Open-angle glaucoma is discussed in Chapter 9, while normal-tension glaucoma is discussed in Chapter 12.

Figure 2.1 Classification of glaucoma by mechanism. Note the main subdivisions are open angle and angle closure.

glaucoma of Atlas 8

CLASSIFICATION BY STAGE OF DISEASE

Classification by stage may be important for setting therapeutic goals, for prognosis, or for disability determinations. Table 2.3 illustrates stages of glaucoma.

CLASSIFICATION BASED UPON THE

INTERNATIONAL CLASSIFICATION

OF DISEASES (ICD-9)

The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) is derived

from a classification of diseases from the World Health Organization. It uses codes to classify all diseases and disorders, originally intended for indexing of hospital records by disease and operations for the purpose of data storage and retrieval. Coding is used for such things as billing and database management. Codes 360–379 cover the eye and adnexa, and the 365 codes include the glaucomas. Table 2.4 lists the ICD-9 codes for glaucoma.

Possible visual field findings

Normal

Normal

Normal or mild diffuse loss of sensitivity, defects generally 10 dB in depth, early nasal step or paracentral depressions, increasing short-term fluctuation

Loss of sensitivity 10–20 dB diffusely or at isolated points or small clusters, well defined nasal steps, focal defects from loss of nerve-fiber bundles

Loss on both sides of the horizontal, large nerve-fiber bundle defects or altitudinal loss, areas of absolute loss

Requires change to larger stimulus size to measure, temporal and central islands remaining

Unmeasurable

365.0Borderline glaucoma (glaucoma suspect)

365.00Preglaucoma, unspecified

365.01Open angle with borderline findings

Open angle with: borderline intraocular pressure, cupping of optic discs

365.02Anatomical narrow angle

365.03Steroid responders

365.04Ocular hypertension

365.1Open-angle glaucoma

365.10Open-angle glaucoma, unspecified

365.11Primary open-angle glaucoma

365.12Low-tension glaucoma

365.13Pigmentary glaucoma

365.14Glaucoma of childhood, infantile or juvenile glaucoma

365.15Residual stage of open-angle glaucoma

365.2Primary angle-closure glaucoma

365.20Primary angle-closure glaucoma, unspecific

365.21Intermittent angle-closure glaucoma

365.22Acute angle-closure glaucoma

365.23Chronic angle-closure glaucoma

365.24Residual stage of angle-closure glaucoma

365.3Corticosteroid-induced glaucoma

365.31Glaucomatous stage

365.32Residual stage

(cont’d)

365.4Glaucoma associated with congenital anomalies, dystrophies, and systemic syndromes

365.41Glaucoma associated with chamber-angle anomalies, Axenfeld’s anomaly (743.44), Reiger’s anomaly or syndrome (743.44)

365.42Glaucoma associated with anomalies of iris aniridia (743.45), essential iris atrophy (364.51)

365.43Glaucoma associated with other anterior segment anomalies, microcornea (743.41)

365.45Glaucoma associated with systemic syndromes, neurofibromatosis (237.7), Sturge–Weber syndrome (759.6)

365.5Glaucoma associated with disorders of the lens

365.51Phacolytic glaucoma

365.52Pseudoexfoliation glaucoma

365.59Glaucoma associated with other lens disorders

365.6Glaucoma associated with other ocular disorders

365.60Glaucoma associated with unspecified ocular disorder

365.61Glaucoma associated with pupillary block

365.62Glaucoma associated with ocular inflammation

365.63Glaucoma associated with vascular disorders

365.64Glaucoma associated with tumors or cysts

365.65Glaucoma associated with ocular trauma

365.8Other specified forms of glaucoma

365.81Hypersecretion glaucoma

365.82Glaucoma associated with increased episcleral venous pressure

365.83Other specific glaucoma

365.9Unspecified glaucoma

Hoskins HD Jr, Kass M. Becker–Shaffer’s Diagnosis and Therapy of the Glaucomas, 6th edn. St Louis, MO: CV Mosby, 1989

Jones MK, Castillo LA, Hopkins CA, Aaron WS, eds. ICD-9-CM Code Book for Physician Payment. Reston, VA: St Anthony Publishing, 1995