CHAPTER 23
Childhood Cataracts and Other Pediatric Lens
Disorders
Disorders of the pediatric lens include, in addition to cataract, abnormalities in lens shape, size, location, and development. Such abnormalities constitute a significant source of visual impairment in children. The incidence of lens abnormalities varies worldwide, ranging from 1:4000 to 1:10,000 per year. Pediatric lens abnormalities must be treated promptly if lifelong vision loss is to be avoided.
See BCSC Section 11, Lens and Cataract, for additional discussion.
Pediatric Cataracts
Cataracts are responsible for nearly 10% of all vision loss in children worldwide. Pediatric cataracts can be
isolated or associated with a systemic condition congenital or acquired
inherited or sporadic unilateral or bilateral partial or complete stable or progressive
General Features
Cataracts in children can be isolated, or they can be associated with a number of conditions, including chromosomal abnormalities, systemic syndromes and diseases, infection, trauma, and radiation exposure. In almost all cases of cataract associated with systemic disease, the cataracts are bilateral; not all bilateral cataracts, however, are associated with systemic disease (Table 23-1). Significant asymmetry can be present in bilateral cases.
Table 23-1
Cataracts can also be associated with other ocular anomalies, including persistent fetal vasculature (discussed later), anterior segment dysgenesis, aniridia, retinal or optic nerve coloboma, and other retinal disorders.
Pediatric cataracts can be congenital or acquired. In general, the earlier the onset, the more amblyogenic the cataract will be. Lens opacities that are visually significant before 2–3 months of age are the most likely to be detrimental to vision.
Most hereditary cataracts are transmitted as an autosomal dominant trait, and they are almost always bilateral. X-linked and autosomal recessive inheritance may also occur. See the Online Mendel ian Inheritance in Man (OMIM) website, which includes the most recent information on genetic disorders with significant involvement of the lens.
Morphology
Cataracts can involve the entire lens (total, or complete, cataract) or only part of the lens structure. The location in the lens and morphology of the cataract provide information about its etiology (Table 23-2), onset, and prognosis. The most common and important clinical morphologies of partial cataracts are discussed in the following subsections.
Table 23-2
Anterior polar cataract
Anterior polar cataracts (APCs) are common and usually less than 3 mm in diameter, appearing as small white dots in the center of the anterior lens capsule (Fig 23-1). They are congenital, usually sporadic opacities. APCs can be unilateral or bilateral. They are usually nonprogressive and visually insignificant. However, unilateral APCs are associated with anisometropia, which may cause amblyopia; thus, careful refraction and follow-up are indicated. Anterior pyramidal cataracts, as the name suggests, have a pyramidal shape and project into the anterior chamber. This cataract is a larger, more severe form of APC that can be progressive and amblyogenic, depending on its size.
Figure 23-1 Anterior polar cataract (arrow). (Courtesy of Gregg T. Lueder, MD.)
Nuclear cataract
Nuclear cataracts are opacities that involve the center, or nucleus, of the lens. They are usually about 3 mm in diameter, but the irregularity of the lens fibers can extend more peripherally. Density and size, however, can vary. These opacities are usually stable, but they can progress. Nuclear cataracts can be unilateral but are more often bilateral. They can be inherited or sporadic. They are congenital but may not be significantly dense at birth (Fig 23-2). Eyes with nuclear cataracts may be smaller than normal and are at risk for developing glaucoma later in childhood.
Figure 23-2 Nuclear cataract. (Courtesy of Ken K. Nischal, MD.)
Lamellar cataract
Identified by their discrete, round shape, lamellar (zonular) cataracts affect 1 or more of the layers of the developing lens cortex surrounding the nucleus. Larger in diameter than nuclear cataracts, these opacities are typically 5 mm or more in diameter (Fig 23-3). They can be unilateral but are more often bilateral. The size and corneal diameter of affected eyes are normal. Because onset is usually after the fixation reflex has been established, patients with lamellar cataracts have a better visual prognosis than patients with cataracts of earlier onset.
Figure 23-3 Lamellar cataract. A, Retroillumination shows size of the lamellar opacity. B, Slit-lamp view shows lamellar opacity surrounding clear nucleus. (Courtesy of David A. Plager, MD.)
Posterior lenticonus
Posterior lenticonus (lentiglobus) is caused by progressive thinning of the central posterior capsule (Fig 23-4A). This thinning initially causes the deformation to have an “oil droplet” appearance on red reflex examination. As the outpouching of the lens progresses, the cortical fibers gradually opacify in the area of the outpouching (Fig 23-4B). This process can take many years, but if the capsule develops a small tear, rapid, total opacification of the lens can occur (Fig 23-4C).
Figure 23-4 Posterior lenticonus/lentiglobus. A, Early clear defect in central posterior capsule and (B) early opacification of central defect. C, Ultrasound biomicroscopy of advanced posterior lenticonus. (Part A courtesy of Edward L. Raab, MD; part B, David
A. Plager, MD; part C, Ken K. Nischal, MD.)
Posterior lenticonus opacities are almost always unilateral, and the affected eye is normal in size. Although the weakness in the posterior capsule may be congenital, the cataract does not usually form until later and therefore behaves like an acquired cataract. The visual prognosis after surgery is usually favorable.
Posterior subcapsular cataract
Posterior subcapsular cataracts (PSCs) are less common in children than in adults. They are usually acquired and bilateral, and they tend to be progressive. Causes of PSC include corticosteroid use, uveitis, retinal abnormalities, and radiation exposure. PSCs can be seen in association with neurofibromatosis 2 and may be the first observable manifestation of this disorder.
Sectoral cataract
Wedge-shaped cortical cataracts are occasionally seen in children. These opacities may be idiopathic, or they may be associated with occult posterior segment tumor, previous blunt trauma, or retinal
coloboma with fibrous bands attached to the posterior lens capsule. Careful posterior segment examination is warranted to rule out these associated pathologies.
Peripheral vacuolar cataract
These asymptomatic peripheral lens vacuoles are sometimes seen in premature infants. The cataracts are most often encountered during examination for retinopathy of prematurity. They are rarely visually significant and usually resolve over time.
Persistent fetal vasculature
Persistent fetal vasculature (PFV; previously called persistent hyperplastic primary vitreous) is the most common cause of a unilateral cataract. It is typically an isolated, sporadic malformation of the eye, but bilateral cases may be associated with systemic or neurologic abnormalities. Usually, affected eyes are smaller than normal.
PFV has a spectrum of severity (Fig 23-5). Features of mild PFV are prominent hyaloid vessel remnants, a large Mittendorf dot, and a Bergmeister papilla. At the other end of the spectrum are microphthalmic eyes with dense retrolental plaques; a thick, fibrous persistent hyaloid artery; elongated ciliary processes (classic for PFV), which may be visible through the dilated pupil; and prominent radial iris vessels. Traction on the optic disc may cause distortion of the posterior retina. Varying degrees of lens opacification occur. The opacity usually consists of a retrolental plaque that is densest centrally and may contain cartilage and fibrovascular tissue.