208 LENS

syndrome. Retinoscopy shows a distorted and myopic reflex; may appear as oil droplet (do not confuse with oil droplet cataract of galactosemia).

Alport’s syndrome: hereditary hemorrhagic nephritis and sensorineural deafness from an X-linked (in 85% of cases) defect of type IV collagen (found in basement membranes) from mutation of the COL4A5 gene at Xq22. Ten to fifteen percent of patients have anterior lenticonus cataracts OU (early) and flecked retinopathy (late) from lens capsule and Bruch’s membrane defects.

MICROSPHEROPHAKIA Small, spherical lens from faulty secondary lens fiber development. Patients are highly myopic; disorder may be isolated or seen with Weill-Marchesani syndrome (most common cause), congenital rubella, Peters’ anomaly, and Marfan, Alport’s, and Lowe’s syndromes.

Weill-Marchesani syndrome: autosomal recessive cause of microspherophakia (lens volume reduced by 25–40%), with lens equator visible through dilated pupil; often dislocates anteriorly or inferiorly (usually in second decade). Also has progressive lenticular myopia of 15–20 D, microcornea, and shallow AC.

Patients have ‘‘antimarfanoid’’ habitus with short stature, broad hands, stubby fingers, bradydactyly, reduced joint mobility, hearing defects, and normal intelligence.

Dominant spherophakia (McGavic type) has been reported as autosomal dominant Weill-Marchesani syndrome but is more like homocystinuria.

Lens can cause pupillary block angle-closure glaucoma that is aggravated by miotics. Thus, treat with cycloplegics to pull the lens–iris diaphragm posteriorly, then perform an LPI.

REMNANTS OF THE TUNICA VASCULOSA LENTIS

Mittendorf ’s dot: remnant of a hyaloid corpuscle seen as a dense white spot inferonasal on posterior lens capsule where the hyaloid artery attached in utero.

Epicapsular star: brown specks on the anterior lens capsule; also called ‘‘chicken tracks.’’

Persistent pupillary membrane: fine filaments arising from the iris collarette to the anterior capsule.

PHPV, retrolental fibroplasia, persistent fetal vasculature (PFV): unilateral eye maldevelopment with cataract, leukocoria, usually small eye in a full-term infant (distinguish from ROP). See Chapter 7.

Metabolic and Degenerative Disease

CATARACT, ACQUIRED, AGE-RELATED Most common cause of visual morbidity worldwide.

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Nuclear sclerosis: slowly progressive, bilateral impairment of distant vision more often than near vision. Often has a myopic shift (‘‘second sight’’ for presbyopic patients), monocular diplopia from abrupt change in refractive index between the sclerotic nucleus and the cortex, or poor blue hue discrimination.

Older nuclear cells lose organelles and cell membranes, with increasing density and dehydration and accumulation of yellow urochrome pigment (possible photo-oxidation product). Pathology shows homogeneity of nucleus, with loss of cellular laminations and increased eosinophilia. When advanced, becomes brown (brunescent) or black (cataracta nigra).

Risk factors: older age, smoking, and lower socioeconomic status

Cortical: soft cataract from changes in ionic composition that lead to cortex hydration and cuneiform opacities; often bilateral but asymmetric. Patients often complain of glare and monocular diplopia. On examination, may see cortical spokes, water clefts, or vacuoles from hydropic swelling of lens fibers; may have secondary cortical changes with crystal formation (cholesterol, calcium oxalate), dystrophic calcification, or even bone or fat formation. Risks include age, diabetes, UV light, and lower socioeconomic status.

Morgagnian globules: spherules of degenerated liquefied lens cortex protein (not cellular accumulation, like the fluid-filled bladder cells seen with PSC).

Mature cataract: intumescent and white total cortical opacity.

Morgagnian cataract: sclerotic nucleus sinks in a bag of liquefied cortex.

Hypermature cataract: cortical material leaks through capsule, leaving it wrinkled and shrunken (may have associated phacolytic glaucoma).

Posterior subcapsular (PSC): axial cupuliform (saucer-shaped) opacities seen typically in younger patients that causes glare and poor photopic vision, especially with miosis, thus reducing near vision more than distant vision. Risk factors include age, diabetes, trauma, steroids, inflammation, ionizing radiation, UV light, and lower socioeconomic status. From posterior migration of lens epithelial cells that form aberrant swollen lens fibers (Wedl or bladder cells).

Anterior subcapsular (ASC): local metaplasia of epithelial cells that synthesize collagenous plaque beneath the anterior capsule. Usually from an injury or irritant or associated with atopic dermatitis.

CATARACT, ACQUIRED, ASSOCIATED WITH OCULAR CONDITIONS Associated with many conditions, including uveitis, PXS, RP, essential iris atrophy, chronic hypotony, glaucoma, myopia, RD, and intraocular tumor (especially ciliary body melanoma).

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210 LENS

Systemic and Vascular Disease

DIABETIC OR SUGAR CATARACT Classic diabetic ‘‘snowflake’’ cataract is bilateral, abrupt, progressive subcapsular lens changes in young patients with uncontrolled diabetes. Senescent cataract is also seen more frequently and earlier. In addition, patients may have earlier presbyopia, decreased amplitude of accommodation, and transient refractive changes (usually myopic) from increased aqueous glucose that enters the lens by diffusion and is converted by aldose reductase to sorbitol, which is not metabolized and causes influx of water and lens swelling.

HYPOCALCEMIA, TETANIC CATARACT Punctate iridescent cortical opacities, usually from idiopathic hypocalcemia or parathyroid removal.

ISCHEMIC CATARACT Anterior segment ischemia (carotid disease, multiple muscle surgeries, etc.) may cause rapidly progressive cataract (usually PSC). Also seen with Takayasu’s arteritis (pulseless disease) and Buerger’s disease (thromboangiitis obliterans).

OTHER SYSTEMIC CAUSES OF CATARACT Hypoparathyroidism, hypothyroidism, cretinism, aminoacidurias, and infantile hypoglycemia

WILSON’S DISEASE, HEPATOLENTICULAR DEGENERATION Autosomal recessive disorder of copper metabolism in which patients may have ‘‘sunflower’’ cataracts from cuprous oxide deposition on the anterior lens capsule and Kayser-Fleischer ring from deposition in Descemet’s membrane.

Physical Disease

CHEMICAL AND ELECTRICAL INJURY Alkali injury is more likely to cause cataract because it penetrates the eye more easily than acid, increasing the aqueous pH and decreasing glucose and ascorbate. Electrical shock may cause protein coagulation and cataract, first seen as vacuoles.

DEPOSITION CATARACT FROM INTRAOCULAR FOREIGN BODY

Chalcosis: copper foreign body may cause deposition in basement membranes (e.g., Descemet’s or the anterior lens capsule), seen as the characteristic ‘‘sunflower’’ cataract (as in Wilson’s disease) but usually not visually significant. If the foreign body is pure copper, patients often have a severe inflammatory reaction.

Siderosis bulbi: from an iron IOFB or hemosiderosis with iron depostion in epithelial and endothelial cells (e.g., the TM, lens epithelium, iris, and retina). When advanced, may see complete cortical cataract.

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DRUG-INDUCED CATARACT OR LENS CHANGES Many drugs are associated with cataract formation.

Amiodarone: may cause stellate anterior axial pigment deposition.

Corticosteroids: one third of patients on chronic dose of prednisone 10 mg/day develop cataract, usually PSC. Cataract may be reversible in children, and any route of steroid therapy (systemic, topical, subconjunctival, nasal sprays, etc.) may lead to cataract.

Miotics and anticholinergics: especially seen with echothiophate iodide and demecarium bromide, primarily in adults (84% of patients have anterior subcapsular vacuoles). Twenty percent of patients after 55 months on pilocarpine develop vacuolar cataracts. Topical anticholinesterases are also associated with large iris cysts.

Phenothiazines: cause pigmented deposits in the anterior lens epithelium; axial but usually not visually significant.

Others: dinitrophenol (formerly used for weight control, as it uncouples oxidative phosphorylation), ergot poisoning, paradichlorobenzene, and Myleran.

RADIATION CATARACT Nearly all forms of radiation have been reported to cause lens changes.

Ionizing radiation: may cause latent cataract up to 20 years later. Younger patients (more actively growing lens cells) are more susceptible. Cataract not typically seen from microwave radiation.

Infrared radiation (‘‘glassblower’s cataract’’): anterior capsular damage causes the capsule to delaminate and ‘‘peel off ’’ (true exfoliation), and the outer lamella scrolls up on itself.

Ultraviolet radiation: UVB increases cortical and PSC cataracts.

Argon laser: blue light is absorbed by yellow sclerotic nucleus.

RESIDUAL CATARACT FOLLOWING CATARACT SURGERY

Elschnig’s pearls: proliferation of residual epithelium cells after cataract extraction form aberrant lens fibers (identical to bladder cells).

Soemmering’s ring: retention of peripheral ring of cortex after cataract extraction.

TRAUMATIC CATARACT Usually seen as a stellate or rosette-shaped axial opacity from blunt injury; may occur with even seemingly minor trauma (e.g., rubber-band snap to eye). Also look for Vossius’ ring from pupillary margin pigment sticking to the anterior capsule following blunt injury. Check for phacodonesis, subluxation, or dislocation, indicative of zonular trauma. If the lens capsule is ruptured by the trauma, lens hydration and rapid opacification are typical. Perforating or penetrating injury may cause complete cataract or focal opacity. Also observe for phacoantigenic uveitis (phacoanaphylactic) if the capsule is open.

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