Ординатура / Офтальмология / Английские материалы / Ocular Pathology_6th edition_Yanoff, Sassani_2009

Disruption of the lens capsule can result in intraocular dispersion of calcified lens particles, resulting in a condition called calcific phacolysis.

F.A break in the anterior capsule may result in cortical material becoming trapped in the equatorial region of the lens (i.e., a Soemmerring’s ring cataract; see Fig.

5.12).

After an acquired break in the lens capsule, or congenitally, mesenchymal tissue may grow into the cataract, leading to bone formation (cataracta ossea) or the formation of adipose tissue (cataracta adiposa or xanthomatosis lentis).

Nucleus (“Hard Cataract”)

I.The increasing pressure of cell on cell, the breakdown of intercellular membranes in the lens nucleus, the slow conversion of soluble to insoluble protein, and the dehydration and accumulation of pigment (urochrome) all lead to optical and histologic densification of the nucleus and a nuclear cataract (Figs 10.23 and 10.24; see Fig. 10.20).

Cigarette smokers have an increased risk for development of nuclear lens opacities.

A.With more and more accumulation of pigment in the nucleus, the nuclear color changes from clear to yellow to brown (cataracta brunescens) to black (cataracta nigra).

B.Both the change in color and the increase in refractive index of the nucleus impede light from entering the eye and cause a decrease in visual acuity.

The increase in index of refraction also causes greater bending of the entering light and results in a lens-induced myopia (“second sight”).

II.Histologically, the changes are usually subtle. Disappearance of the usual artifactitious nuclear clefts is noted.

A.The nucleus appears as an amorphous, homogeneous mass, with increased eosinophilia.

Crystals such as calcium oxalate (see Fig. 10.24) may be deposited in the nucleus.

B.As seen by electron microscopy, the cells are very elec- tron-dense, exceedingly folded, and tightly packed, with obliteration of the intercellular spaces.

Age-Related (Senile) Cataracts

I.Age-related cataracts consist of any cataracts without a known cause that develop in elderly people (Fig. 10.25).

A.Clinically, age-related cortical cataracts can be divided into three main types: (1) cuneiform (in the peripheral cortex); (2) punctate perinuclear (in the cortex next to the nucleus); and (3) cupuliform (in the posterior cortex).

B.A nuclear cataract is merely the acceleration of the normal densification process of the innermost lens fibers.

II.Age-related cataracts may subluxate or dislocate spontaneously. The histologic features of cortical and nuclear cataracts were described previously.

SECONDARY CATARACTS

Intraocular Disease

I.Uveitis, malignant intraocular tumors (see Fig. 10.17), glaucoma, and retinitis pigmentosa (see Fig. 10.16C) can cause secondary cataracts.

The cataract secondary to intraocular disease has been termed a complicating cataract (cataracta complicata). Diseases in the anterior part of the eye tend to cause anterior cataract (anterior subcapsular, anterior cortical, or both), whereas diseases in the posterior part of the eye tend to cause posterior cataract (PSC, posterior cortical, or both).

II.Histologically, the lens changes are nonspecific and are the same as those described previously.

Trauma

See p. 115–117 in Chapter 5.

lens epithelial cells (see Fig. 10.26), and in chalcosis, where copper is deposited in the lens capsule.

Endocrine, Metabolic, and Others

I.Cataracts may occur in conditions such as diabetes mellitus (see p. 596 in Chapter 15), galactosemia, hypoparathyroidism, hypothyroidism, aminoacidurias such as Lowe’s syndrome (see section Capsule, earlier), myotonic dystrophy (see p. 538 in Chapter 14), dermatologic disorders (e.g., atopic dermatitis, chronic eczema, erythema multiforme), and chromosomal abnormalities.

A. Galactosemia

Toxic

I.Drugs such as steroids (topical, inhaled, and systemic), MER 29, phospholine iodide, Myleran, the phenothiazines and dinitrophenol, amiodarone, allopurinol, along with toxic substances such as ergot or metallic foreign bodies [e.g., iron (Fig. 10.26; see also Figs 5.49 and 5.50) or

copper (see Fig. 8.53)], can cause cataracts.

II.Histologically, the lens changes are nonspecific except in siderosis and hemosiderosis lentis, where iron is present in

Galactosemia, glucose-6-phosphate dehydrogenase deficiency, and riboflavin deficiency are conditions in which cataracts represent a sensitive indicator of metabolic abnormalities of erythrocytes.

1.Galactosemia is an autosomal-recessively inherited condition (homozygous) resulting from a deficiency of the enzyme galactose-1-phosphate uridyl transferase.

2.The cataract is usually noted a few days to a few months after birth.

a.In latent galactosemia, however, cataracts may not develop in some patients until they are 1 year of age or even older. In such cases of juvenile cataract, the galactosemia may not be evident

and can only be discovered by means of an abnormal galactose loading test result or a raised fasting blood galactose.

b.Galactosemia may be associated with cataracts that develop in early and middle adulthood in heterozygous patients.

A

C

B.Clinically and histologically, the lens changes tend to be nonspecific.

COMPLICATIONS OF CATARACTS

Glaucoma

I.Mechanical

A.An intumescent cataract may cause pupillary block and secondary angle closure.

B.A cataract may spontaneously dislocate anteriorly and cause a pupillary block directly (see Fig. 5.38), or it may dislocate posteriorly and cause a pupillary block indirectly by prolapsing vitreous into the pupil.

II.Phacolytic glaucoma

A.Phacolytic glaucoma (Fig. 10.27) is a secondary openangle glaucoma characterized clinically by signs and symptoms of acute glaucoma, except that the anteriorchamber angle is open, a white cataract is noted, and a milky material may be seen in the anterior chamber.The glaucoma may resemble an open-angle glaucoma secondary to an anterior uveitis, except that keratic precipitates are usually absent.

B

Fig. 10.27 Phacolytic glaucoma. A, Patient presented with signs and symptoms of acute closed-angle glaucoma. Chalky material seen in anterior chamber. The angle was open. B, Histologic section of another case shows hypermature cataract. Most of the cortex has leaked through the intact capsule. Lens-filled macrophages present in anterior chamber, on iris surface, in iris stroma, and clogging anterior-chamber angle, shown at increased magnification in C. (A, Courtesy of Dr. TR Thorp.)

B.Phacolytic glaucoma occurs in an eye with a hypermature (white) cataract.

1.Liquefied, denatured lens material leaks out of the lens through a generally intact lens capsule into the aqueous fluid.

Often, polychromatic, hyperrefringent crystalline particles are noted on the milky material in the anterior chamber.

The particles are presumably composed of cholesterol.

2.The lens material in the aqueous incites a macrophagic cellular response.

Liquefied or denatured protein does not seem capable of inciting an antigen–antibody response, only a macrophagic response. Relatively normal lens protein (i.e., not liquefied or denatured), if an abrogation of tolerance to lens protein has occurred, is capable of inciting an antigen–antibody reaction. The result is phacoanaphylactic endophthalmitis (see p. 75 in Chapter 4).

3.The macrophages engulf the liquefied lens material and obstruct an open anterior-chamber drainage angle, causing an acute rise in the intraocular pressure.

In addition to macrophages filled with denatured lens material, aggregates of high-molecular-weight soluble protein (molecular weight 1.5 × 108) in the anteriorchamber angle may play a role in obstructing aqueous outflow.

C.In 25% of enucleated eyes that show phacolytic glaucoma, a postcontusion deformity of the anteriorchamber angle suggests that trauma may have been the event initiating cataract formation.

D.Histologically, a hypermature cataract is found.

1.Macrophages filled with eosinophilic lens material are seen in the aqueous fluid and on and in the iris, occluding the anterior-chamber angle.

2.The macrophages are not present on the corneal endothelium.

Phacoanaphylactic Endophthalmitis

See p. 75 in Chapter 4.

ECTOPIC LENS

Congenital

I.Congenital ectopia of the lens is usually bilateral and associated with generalized malformations or systemic disease such as homocystinuria, Marfan’s syndrome, or Weill–Marche- sani syndrome, or less frequently with cutis hyperelastica

(Ehlers–Danlos syndrome), proportional dwarfism, oxycephaly, Crouzon’s disease, Sprengel’s deformity, genetic spontaneous late subluxation of the lens, or Sturge–Weber syndrome. Only the first three are described.

A. Homocystinuria (Fig. 10.28)

1.Homocystinuria is a systemic disease characterized by fair hair and skin, malar flush, poor peripheral circulation, frequent skeletal abnormalities (osteoporosis, arachnodactyly, pectus excavatum, or pectus carinatum), mental retardation, shortening of platelet survival time, and progressive arterial thrombosis.

Thromboembolic phenomena are common in patients who have homocystinuria, especially during or after general anesthesia.

2.Ocular findings include ectopia lentis (often luxated into the anterior chamber or subluxated inferonasally) and peripheral chorioretinal degeneration.

3.The disease, which is caused by a deficiency or absence of cystathionine synthetase, is transmitted by an autosomal-recessive gene. A metabolic block between homocysteine and cystathionine results in the accumulation of homocystine.

4.Histology

a.A thick, periodic acid–Schi (PAS)-positive, amorphous material overlies the nonpigmented ciliary epithelium.

b.The material is made up of short segments of normal zonules composed of oriented filaments intermingled with myriad short filaments in disarray; the number of abnormal filaments appears to increase with age as the number of normal zonular fiber fragments decreases.

A similar collection or fringe of a mixture of very short, disorganized filaments, together with a few aligned groups of filaments like those present in normal zonules, is found attached to the anterior lens capsule (see Fig. 10.28A). The lens fringe of white zonular remnants is characteristic of homocystinuria. The zonular breakdown and degeneration, even dissolution, result in the ectopic location of the lens.

c.Degeneration of the nonpigmented ciliary epithelium and peripheral neural retina is often present and increases in severity with age.

B.Marfan’s syndrome (arachnodactyly, dystrophia mesodermalis hypoplastica; Figs 10.29 and 10.30)

1.Marfan’s syndrome consists of ocular, skeletal, and cardiovascular abnormalities.

2.Urinary excretion of hydroxyproline may be present or even excessive, but it may also be normal (i.e., absent).

An attenuation, probably of nonenzymatic steps involved in the maturation of collagen, causes defective collagen organization in the connective tissue of patients. The defect resides on chromosome 15q15–21. The responsible gene is fibrillin-1 (FBN1). The estimated prevalence is 2 to 3 per 10 000 individuals.

3.The lens may be subluxated in any direction, but usually superotemporally.

4.Other ocular anomalies include iridodonesis, hypoplasia of the iris, increased positive transillumination of the iris, miosis with decreased ability to dilate, and a fetal anterior-chamber angle.

5.The condition is usually inherited as an autosomaldominant trait, often with variable degrees of expression.

The condition can also occur de novo, with a mutation rate of 0.7 per 100 000 births.

6.Histology

a.The anterior-chamber angle shows an immature configuration, but this is variable and nonspecific.

b.The iris may show segmental hypopigmentation or absence of pigment from the posterior layer of the pigment epithelium, especially toward the

periphery, with accompanying hypoplasia of the overlying iris dilator muscle.

The hypopigmentation of the posterior iris pigment epithelial layer, when present, is highly characteristic and explains the clinical observation of increased positive retroillumination of the iris diaphragm where stromal pigmentation is not too dense.

c.The ciliary body processes or crests may extend sporadically on to the back of the iris and may be maldeveloped.

d.The lens is subluxated in the posterior chamber or dislocated into the anterior chamber or vitreous compartment.

The area of interface between lens capsule and zonular fibers appears abnormal. The zonular attachments seem blunted and rounder than in the normal attachment. It is probably the abnormality of the lens

capsule–zonular adhesion area that results in the ectopia of the lens.

e.Qualitative abnormalities in fibrillin-1 staining can be seen in the conjunctiva

C.Weill–Marchesani syndrome

1.Weill–Marchesani syndrome is a generalized disorder of connective tissues characterized by spherophakia, ectopia lentis, brachymorphism, and joint sti ness.

2.The spherophakic lens subluxates frequently, usually in a down-and-in direction. High myopia is often present.

Spherophakia may be part of the Weill–Marchesani syndrome and may occur independently, or, rarely, may occur in Marfan’s syndrome. The small lens can cause pupillary block glaucoma. Such glaucoma is worsened by miotics but ameliorated by mydriatics. Peripheral anterior synechiae may form secondarily to the pupillary block. The small lens may dislocate into the anterior chamber.