Congenital cataracts are present at birth but may not be identified immediately. Infantile cataracts develop during the first year of life. Because some lens opacities escape detection at birth and are noted only on later examination, these terms are used interchangeably by many physicians. In this book, the term congenital cataract is used for both categories of lens opacities. These cataracts are fairly common, occurring in 1 of every 2000 live births, and cover a broad spectrum of severity. While some lens opacities do not progress and are visually insignificant, others can cause profound visual impairment.
Congenital cataracts may be unilateral or bilateral. They can be classified by morphology, presumed or defined genetic etiology, presence of specific metabolic disorders, or associated ocular anomalies or systemic findings (Table 4-2). In general, approximately one-third of congenital cataracts are a component of a more extensive syndrome or disease (eg, cataract resulting from congenital rubella syndrome), one-third occur as an isolated inherited trait, and one-third result from undetermined causes. Metabolic diseases tend to be more commonly associated with bilateral cataracts. (For a discussion of the evaluation of pediatric patients with congenital cataracts, see BCSC Section 6, Pediatric Ophthalmology and Strabismus.) Congenital cataracts occur in a variety of morphologic configurations, including lamellar, polar, sutural, coronary, cerulean, nuclear, capsular, complete, membranous, and rubella.
Table 4-2 Etiology of Pediatric Cataracts
Of the congenital cataracts, lamellar, or zonular, cataracts are the most common type (Fig 4-11). They are characteristically bilateral and symmetric, and their effect on vision varies with the size and density of the opacity. Lamellar cataracts may be inherited as an autosomal dominant trait. In some cases, they may occur as a result of a transient toxic influence during embryonic lens development. The earlier this toxic influence occurs, the smaller and deeper is the resulting lamellar cataract.
Lamellar cataracts are opacifications of specific layers or zones of the lens. Clinically, the cataract is visible as an opacified layer that surrounds a clearer center and is itself surrounded by a layer of clear cortex. Viewed from the front, the lamellar cataract has a disc-shaped configuration. Often, additional arcuate opacities within the cortex straddle the equator of the lamellar cataract; these horseshoe-shaped opacities are called riders.
Figure 4-11 Lamellar cataract. A, Lamellar cataract, slit-lamp view. B, Lamellar cataract viewed by retroillumination. C, Schematic of lamellar cataract.
(Part C illustration by Mark Miller.)
Polar cataracts are lens opacities that involve the subcapsular cortex and capsule of the anterior or posterior pole of the lens. Anterior polar cataracts are usually small, bilateral, symmetric, nonprogressive opacities that do not impair vision (Fig 4-12). Most commonly, they are congenital and sporadic, but they may be inherited in an autosomal dominant pattern. Anterior polar cataracts are sometimes seen in association with other ocular abnormalities, including microphthalmos, persistent pupillary membrane, and anterior lenticonus. They usually do not require treatment but often cause anisometropia.
Posterior polar cataracts are generally associated with more profound decrease in vision than anterior polar cataracts, because they tend to be larger and are positioned closer to the nodal point of the eye. Capsular fragility has been reported in association with these cataracts, which are usually stable but occasionally progress. They may be familial or sporadic. Familial posterior polar cataracts are usually bilateral and inherited in an autosomal dominant pattern. Sporadic posterior polar cataracts are often unilateral and may be associated with remnants of the tunica vasculosa lentis or with an abnormality of the posterior lens surface such as lenticonus or lentiglobus.
The sutural, or stellate, cataract is an opacification of the Y-sutures of the fetal nucleus (Fig 4-13). It usually does not impair vision. These opacities often have branches or knobs projecting from them. Sutural cataracts are bilateral and symmetric and are frequently inherited in an autosomal dominant pattern.
Coronary cataracts are so named because they consist of a group of club-shaped cortical opacities that are arranged around the equator of the lens like a crown, or corona. They cannot be seen unless the pupil is dilated, and they usually do not affect visual acuity. Coronary cataracts are often inherited in an autosomal dominant pattern.
Figure 4-12 Anterior polar cataract. A, Anterior polar cataract, slit-lamp view. B, Anterior polar cataract viewed by retroillumination.
Figure 4-13 Sutural cataract.
Also known as blue-dot cataracts, cerulean cataracts are small bluish opacities located in the lens cortex (Fig 4-14). They are nonprogressive and usually do not cause visual symptoms.
Congenital nuclear cataracts are opacities of the embryonic nucleus alone or of both embryonic and fetal nuclei (Fig 4-15). They are usually bilateral, with a wide spectrum of severity. Lens opacification may involve the complete nucleus, or it may be limited to discrete layers within the nucleus. Eyes with congenital nuclear cataracts tend to be microphthalmic, and they are at increased risk of developing aphakic glaucoma.
Capsular cataracts are small opacifications of the lens epithelium and anterior lens capsule that spare the cortex. They are differentiated from anterior polar cataracts by their protrusion into the anterior chamber. Capsular cataracts generally do not adversely affect vision.
In cases of complete, or total, cataract, all of the lens fibers are opacified. The red reflex is completely obscured, and the retina cannot be seen with either direct or indirect ophthalmoscopy. Some cataracts may be subtotal at birth and progress rapidly to become complete cataracts. Complete cataracts may be unilateral or bilateral, and they cause profound visual impairment.
Membranous cataracts occur when lens proteins are resorbed from either an intact or a traumatized lens, allowing the anterior and posterior lens capsules to fuse into a dense white membrane (Fig 4-16). The resulting opacity and lens distortion generally cause significant visual disability.
Figure 4-14 Cerulean cataract.
(Courtesy of Karla J. Johns, MD.)
Figure 4-15 Congenital nuclear cataract.
(Reproduced from Day SH. Understanding and Preventing Amblyopia: Slide & Script Presentation. Eye Care Skills for the Primary Care Physician Series. American Academy of Ophthalmology; 1987.)
Maternal infection with the rubella virus, an RNA togavirus, can cause fetal damage, especially if the infection occurs during the first trimester of pregnancy. Cataracts resulting from congenital rubella syndrome are characterized by pearly white nuclear opacifications. Sometimes the entire lens is opacified (complete cataract), and the cortex may liquefy (Fig 4-17). On histologic examination, lens-fiber nuclei are retained deep within the lens substance. Live virus particles may be recovered from the lens as late as 3 years after the patient’s birth. Cataract removal may be complicated by excessive postoperative inflammation caused by release of these particles. (See also BCSC Section 6, Pediatric Ophthalmology and Strabismus.) Other ocular manifestations of congenital rubella syndrome include diffuse pigmentary retinopathy, microphthalmos, glaucoma, and transient or permanent corneal clouding. Although congenital rubella syndrome may cause cataract or glaucoma, both conditions are usually not present simultaneously in the same eye.
Figure 4-16 Membranous cataract.
Figure 4-17 Rubella cataract.
(Courtesy of Thomas L. Steinemann, MD.)
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.