Ординатура / Офтальмология / Английские материалы / Clinical Pathways in Glaucoma_Zimmerman, Kooner_2001

Figure 10–1. Glaucoma and ectopia lentis: differential diagnosis.

Can Ectopia Lentis be Nontraumatic?

For nontraumatic lens dislocations, the diagnostic workup of the glaucoma is similar in most entities.4,5

192 Glaucoma Associated with Lens Disorders

Are There Typical Systemic Abnormalities?

One must elicit a complete medical history to look for specific clinical features that are typical of syndromes associated with ectopia lentis. A referral for a comprehensive medical evaluation is essential. If systemic features are absent, the examination of the pupils will help narrow the differential diagnosis. These features are listed when each entity is addressed separately. One should know the typical clinical components of the most common systemic disorders associated with ectopia lentis as listed in Table 10–1. The importance of this assessment cannot be overemphasized because potentially serious systemic complications can be present when ectopia lentis is first diagnosed by the ophthalmologist. The occurrence and mechanisms of glaucoma in the most common congenital syndromes are compared in Table 10–3.

Are Both Pupils Eccentric (“Ectopic”)?

In this case, ectopia lentis et pupillae is the most likely diagnosis. This is an autosomal recessive condition in which both pupils are displaced in one direction and the lenses dislocated in the opposite direction. In some cases the lenses are small and spherical.5 Peripheral transillumination defects can be present in an iris that dilates poorly. Systemic abnormalities are usually absent. Glaucoma most commonly results from lens dislocation and secondary pupillary block.4–6 Concurrent ocular pathology includes cataract, severe axial myopia, and retinal detachment. Rarely, these patients may have marfanoid features.7

Are the Pupils in Normal Position?

If this is the case, exfoliation syndrome should be first excluded by careful anterior segment biomicroscopy. The presence of a dandruff-like material at the pupillary margin or lens surface and patchy pigment deposition at the angle will alert the examiner. In the absence of exfoliation, the diagnosis of simple ectopia lentis must be entertained. This syndrome is often inherited in an autosomal dominant fashion, although recessive transmission has been documented. The subluxation is usually bilateral, and sometimes asymmetric.1 The lenses are usually displaced superiorly and laterally and in severe cases they can dislocate into the anterior chamber.4, 5 The dislocation can occur during the first decade (congenital type) or later in life (spontaneous type). Abnormalities in chromosome 15 (fibrillin gene) have been reported in a congenital case.8 A paucity of normal zonular fibers has been found in some cases.9 Glaucoma usually results from lens-induced secondary pupillary block in advanced stages10 and is more common in the late type of subluxation.5 Vitreous herniation can play a role in the pathogenesis of the pupillary block. When open, the anterior chamber angle has a normal appearance. Cataracts and retinal detachment can be present.4,5

Is Microspherophakia Present?

As the name implies, the lens diameter is decreased and the axial thickness is increased. The most common entity associated with microspherophakia is

Weill-Marchesani syndrome.4 In addition, a hereditary combination of microspherophakia, ectopia lentis, and glaucoma has been recognized. This triad can also be associated with Marfan syndrome, homocystinuria, and other syndromes not usually linked to microspherophakia.5 Microspherophakia can also occur as an isolated feature.11

Does the Patient Have Systemic Features Typical of WeillMarchesani Syndrome?

This autosomal recessive syndrome has striking phenotypic features that contrast with those seen in Marfan patients. Patients are short and stocky, with brachycephalia and a depressed nasal bridge. The hands and fingers are short and stubby, and the joints lack good mobility.5

What Is the Pathogenesis of the Glaucoma

in Weill-Marchesani Syndrome?

Glaucoma occurs more often in Weill-Marchesani syndrome than in Marfan syndrome or homocystinuria,12,13 usually during the third or fourth decade of life. The dimensions of the lens (25% smaller, 25% thicker)4 create zonular elongation, rupture, and lens dislocation. Anterior migration of the lens usually induces glaucoma either by blocking the pupil posteriorly or by total luxation into the anterior chamber.12,14 In recurrent or chronic pupillary block the apposition of the peripheral iris to the cornea can result in peripheral anterior synechiae (PAS) and trabecular damage. In some cases, glaucoma occurs in the absence of lens dislocation, suggesting an open-angle mechanism (trabecular or angular abnormality).12 In the presence of elongated zonules, mid-dilation can precipitate acute angle-closure glaucoma even in the absence of ectopia lentis.15 Abnormal anterior chamber angles (abundant iris processes, iris root fraying) have been described but are not specific of this syndrome.16

Does the Patient Have Features Typical

of Marfan Syndrome?

Patients with this autosomal dominant syndrome are tall, with slender fingers and toes (arachnodactyly), hyperflexible joints, and severe scoliosis resulting in pectus excavatum.5 Mutations on chromosome 15 can affect the synthesis of fibrillin, a connective tissue protein present in the zonules.17 Chromosome 5 mutations have also produced a similar syndrome.18 Cardiovascular abnormalities include aortic dilatation and dissecting aneurysm as well as mitral valve insufficiency.5

What is the Pathogenesis of the Glaucoma in Marfan Syndrome?

Marfan syndrome is associated with ectopia lentis in up to 80% of cases.4 The lens is usually displaced superiorly and frequently temporally. The lens zonules are reduced in number but structurally normal, which explains the

Is the Lens in the Anterior Chamber?

In this case, if the lens is clear and pupillary block is not present, the initial management can be conservative. An attempt to reposition the lens can be made by maximally dilating the pupil and placing the patient in a supine position. Manual indentation of the central cornea has been successful as an adjunctive measure.24 If these measures are successful, a laser PI will prevent the recurrence of pupillary block, and chronic miotics will keep the lens in the posterior chamber. If these measures fail (the clear lens remains in the anterior chamber or adheres to the cornea) lens extraction is indicated to prevent further complications.

If pupillary block is present, the condition represents a true emergency because the IOP is usually very high. Delayed treatment will result in irreversible damage to the nerve, cataract formation, or corneal decompensation. The block occurs between the anterior iris and the posterior surface of the dislocated lens or as a direct pupillary occlusion by an entrapped lens. Initial measures should include hyperosmotics, aqueous suppressants, and placing the patient in a supine position. A laser PI can next be performed to relieve the pupillary block.1,4

If these measures are successful, the IOP will decrease and the anterior chamber will deepen as the angle opens. One then faces the following therapeutic alternatives. If the lens is cataractous, miotic therapy can keep the lens in the anterior chamber in preparation for lens extraction via a limbal approach. If the lens is clear, maximal pupillary dilatation after the resolution of the pupillary block may allow the lens to fall backward, and then it is managed with miotics as described above. If the lens remains in the anterior chamber despite medical therapy and PI, lens extraction is indicated.

Future Considerations

The key to successful management of this condition is early diagnosis. Prompt referral to an ophthalmologist will prevent life-threatening complications that can occur with some congenital syndromes. New techniques and instrumentation have made the surgical management of these conditions much safer. At this time, pars plana vitrectomy techniques with ultrasonic lens fragmentation offer a successful alternative both in adults25 and in children.26

GLAUCOMA ASSOCIATED

WITH CATARACT FORMATION

Definition

How Is Glaucoma Associated with Cataract Formation Defined?

Cataract and glaucoma can be present in an eye in three different situations:

(1) they can coexist independently, (2) both can be the result of the same pathologic process (e.g., trauma, inflammation), and (3) one can be the result of the

198 Glaucoma Associated with Lens Disorders

other one. This section specifically addresses the third situation, where glaucoma is in some way the result of cataract formation or its complications.

Epidemiology and Importance

Both glaucoma and cataract independently increase in prevalence with age; therefore, they commonly coexist in the elderly. The Beaver Dam Eye Study evaluated these two issues in a large population study.27, 28 The overall prevalence of primary open-angle glaucoma (POAG) was 2.1%, ranging from 0.9% in persons 43 to 54 years of age to 4.7% in persons 75 years of age and older.27 There was no significant effect of sex after adjusting for age. It is known that the prevalence of POAG is higher in black populations (see Chapter 2). The prevalence of age-related cataracts increased with age for both sexes, with women being more severely affected than men. Overall, 17.3% of patients had nuclear sclerosis and 6% had posterior subcapsular opacities.28 On the other hand, the occurrence of lens-related glaucoma is strongly linked to the duration of the cataract, with most types of glaucomas occurring in long-standing cataracts.29-31 Cataracts in the United States are removed relatively earlier than in the developing world. An average preoperative visual acuity of 20/60 was determined in one study.29 As a result, a lower incidence of lens-related glaucomas can be expected. More specific epidemiologic data is presented when each entity is discussed separately.

We are offered a unique opportunity to successfully treat the glaucoma by addressing the lens condition. With a better understanding of the mechanisms of disease, the terminology has become less confusing. Currently accepted definitions will be used to discuss this fascinating group of diseases.

How Is Glaucoma Associated

with Cataract Formation Classified?

Once again, the appearance of the angle and the mechanism of disease represent the major criteria to classify these entities. Table 10–4 outlines the etiologic

Table 10–4. Lens-Related Open-Angle Glaucomas

ALT, argon laser trabeculoplasty; GAG, glycosaminoglycan.

Table 10–5. Mechanisms of Glaucoma Associated to Cataract Formation

Open-angle glaucoma (lens-induced glaucoma) Lens particle glaucoma

Phacolytic (lens protein) glaucoma Phacoanaphylactic glaucoma

Angle-closure glaucoma Pure pupillary block*

Primary angle-closure glaucoma Lens enlargement + pupillary block

Phacomorphic glaucoma (intumescent lens)

Angle-closure glaucoma + large cataract (nonintumescent lens)**

*A normal-sized lens in a small globe can generate pupillary block. This in essence represents a type of lensinduced glaucoma.

**A large cataractous lens in a small or normal-sized globe can generate pupillary block, and a mechanical posterior “pushing” (phacomorphic) mechanism can be present as well.

and pathogenic factors involved in the production of the different cataractrelated open-angle glaucomas. Table 10–5 describes the various mechanisms of glaucoma associated to cataract formation. Due to the association of phacoanaphylaxis with cataract surgery, this entity is discussed in a different section (see Glaucoma Associated with Aphakia and Pseudophakia, below).

Diagnosis and Differential Diagnosis

How Is Glaucoma Associated

with Cataract Formation Diagnosed?

A good history and careful examination are always essential. As we determine the mechanisms of disease acting in a given patient we can then make the appropriate diagnosis and plan the treatment accordingly. Figure 10–3 outlines the diagnostic process and the differential diagnosis of these conditions. The management of these conditions will be discussed separately when each entity is discussed.

Is There a History of Trauma?

Glaucoma associated with ocular trauma is discussed in Chapter 13. Nevertheless two specific clinical entities caused by lens trauma are discussed in this chapter as they represent types of glaucoma essentially caused by lens-related mechanisms. These two are lens particle glaucoma and phacoanaphylactic glaucoma. The status of the lens capsule is the next question to be considered.

Has the Lens Capsule been Violated?

Capsular disruption can result from trauma, either surgical (extracapsular cataract extraction) or nonsurgical (penetrating). In both instances lens particles are released and continuously exposed to the inner ocular environment.31