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 etiology (Table 23-2), onset, and prognosis. Important types and causes of cataract in children are discussed in the following sections.
Table 23-2 Morphology and Etiology of Select Pediatric Cataracts
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, perhaps more appropriately termed anterior lens opacities. 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. It is often associated with cortical changes that can be progressive and amblyogenic, depending on the size of the opacity.
Infantile nuclear cataract
Nuclear cataracts are opacities that involve the center, or nucleus, of the lens. They are usually approximately 3 mm in diameter, but the irregularity of the lens fibers can extend more peripherally. Density and size can vary. Infantile nuclear cataracts may not be significantly dense at birth (Fig 23-2). They can be inherited or sporadic and are more commonly bilateral. These opacities are usually stable, but they can progress. Eyes with nuclear cataracts may be smaller than normal.
Figure 23-1 Anterior polar cataract (arrow).
(Courtesy of Gregg T. Lueder, MD.)
Figure 23-2 Congenital nuclear cataract.
(Courtesy of Ken K. Nischal, MD.)
Lamellar (zonular) cataracts affect one or more of the layers of the developing lens cortex surrounding the nucleus. Affected lenses have a clear center, a discrete lamellar opacity, and a clear peripheral cortex. Larger 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. Lamellar cataracts are often less dense than other forms of infantile cataracts, and therefore the visual prognosis is usually better.
Posterior lenticonus is a cone-shaped deformation of the posterior lens surface caused by progressive thinning of the central capsule (Fig 23-4A); when the deformation is spherical, it is referred to as lentiglobus. This thinning initially causes the lens to have an “oil droplet” appearance on red reflex examination. As the outpouching of the lens progresses, the surrounding cortical fibers gradually opacify (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 23-3 Lamellar cataract. A, Retroillumination shows the size of the lamellar opacity. B, Slit-lamp view shows a lamellar opacity surrounding clear nucleus.
(Courtesy of David A. Plager, MD.)
Figure 23-4 Posterior lenticonus. A, Early clear defect in the central posterior capsule. B, Opacification of the 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.)
The 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 thus behaves like an acquired cataract. The visual prognosis after cataract surgery is usually favorable.
Posterior subcapsular cataract
Posterior subcapsular cataracts (PSCs) are less common in children than in adults. They are usually acquired and are often bilateral. PSCs tend to progress. Causes of PSC include corticosteroid use, uveitis, retinal abnormalities, radiation exposure, and trauma. PSCs can be seen in association with neurofibromatosis type 2 and may be the first observed manifestation of this disorder.
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, vitreoretinopathies, or retinal coloboma with fibrous bands attached to the posterior lens capsule. Careful posterior segment examination is indicated 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 spontaneously.
Persistent fetal vasculature
Persistent fetal vasculature (PFV; previously called persistent hyperplastic primary vitreous) is the most common cause of a unilateral cataract. PFV is typically an isolated, sporadic ocular malformation, but bilateral cases may be associated with systemic or neurologic abnormalities. Usually, affected eyes are smaller than normal.
PFV ranges in severity from mild to severe (Fig 23-5). Features of mild PFV are prominent hyaloid vessel remnants, a large Mittendorf dot, and 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.
Figure 23-5 Persistent fetal vasculature (PFV). A, Mild variant with central retrolental membrane. B, Elongated ciliary processes are adherent to the lens. Note the dense fibrous plaque on the posterior lens capsule. C, Ultrasonogram of an eye with PFV. Note the dense stalk arising from the optic nerve and attaching to the posterior lens.
(Part A courtesy of David A. Plager, MD; part C courtesy of Edward L. Raab, MD.)
The natural history of more severely affected eyes is usually one of progressive cataract formation and anterior chamber shallowing, causing secondary glaucoma. The glaucoma can occur acutely because of rapid, total lens opacification and swelling, or it may develop gradually, over years. Congenital retinal nonattachment, ciliary body detachment, vitreous hemorrhage, and optic nerve dysmorphism are other features of severe PFV.
Retinoblastoma may be part of the initial differential diagnosis of PFV because of leukocoria. The presence of microphthalmia and cataract are important factors in the differentiation of these disorders, as retinoblastoma is rarely found in microphthalmic eyes, and cataracts are very unusual in retinoblastoma.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.