Introduction

Lens disorders in the pediatric population consist of both congenital and acquired abnormalities. They include structural anomalies as well as opacities (cataracts). These conditions are a significant source of visual impairment in children. The primary source of vision loss in children with cataracts is amblyopia, which may be severe and permanent. The goal in management is to maximize visual potential and minimize associated complications. Early detection of these disorders is a critical step in allowing for optimal management and intervention.

The crystalline lens is a biconvex, transparent structure that functions to refract light and provide accommodation. It consists of a central nucleus (embryonal and fetal), surrounded by cortex, lens epithelium, and lens capsule (94). The lens develops from central to peripheral. As the fetal nucleus forms around the embryonal nucleus, the cells and fibers come together anteriorly and posteriorly to form sutures in the shape of a Y. The anterior Y-suture is upright and the posterior Y-suture appears inverted. The locations of these sutures mark the extent of the lens nucleus. Based on our knowledge of the timing of development of the various lens structures, it is possible to estimate at what stage a particular abnormality may have arisen based on its specific location.

94

94 Cross-section of the human crystalline lens, showing its relationship to surrounding ocular structures. (Illustration by Christine Gralapp.

Reproduced,with permission,from Johns KJ,

Basic and Clinical Science Course:Cataract and Lens,Section 11,AmericanAcademy of Ophthalmology,2001–2002.)

Structural lens abnormalities

Aphakia

Congenital absence of the lens is extremely rare. It is typically associated with other profound abnormalities of the eye.

Spherophakia (microspherophakia)

The lens is smaller and more spherical in shape than a normal lens. It is most commonly bilateral and is associated with high myopia due to the increased curvature of the anterior and posterior lens surfaces. There is a high incidence of pupillary block glaucoma, which may result from the lens dislocating anteriorly. There is a strong association of spherophakia with Weill–Marchesani syndrome, which is a rare disorder involving primarily ocular and skeletal abnormalities.

Coloboma

Coloboma may affect various ocular structures including the iris, lens, retina, and optic nerve. A lens coloboma typically presents as a localized flattening or notching of the lens at its periphery. The most common location is inferonasal. They may be unilateral or bilateral and are frequently associated with irregular astigmatism and anisometropia (if unilateral or asymmetric).

Subluxation (ectopia lentis)

The lens is displaced from its normal location (centered in the pupil). It is typically bilateral, but may be unilateral if acquired. The systemic condition most commonly associated with lens subluxation is Marfan’s syndrome (95, 96).1 Other conditions include homocystinuria, hyperlysinemia, sulfite oxidase deficiency, Ehlers–Danlos syndrome, and Weill–Marchesani syndrome. There is also an isolated lens subluxation that follows an autosomal dominant inheritance pattern. Ectopia lentis et pupillae involves subluxed lenses and eccentrically displaced pupils as well.

Depending on the severity, lens subluxation may be associated with high degrees of refractive errors (myopia and astigmatism) and often leads to amblyopia, which may be severe. Lensectomy is indicated if the lens edge is visible in the pupil or if adequate optical correction is not possible with glasses or contact lenses.

Lenticonus

Lenticonus is a central bowing of the anterior or posterior lens capsule. Anterior lenticonus may be associated with Alport syndrome, which also involves sensorineural deafness and nephritis. Posterior lenticonus is typically sporadic and isolated. Either form may be associated with amblyopia due to irregular astigmatism or cataract formation.

Persistant fetal vasculature

Persistant fetal vasculature (PFV), formerly known as persistent hyperplastic primary vitreous (PHPV), is a disorder characterized by persistence of the primitive hyaloid vascular system. This vascular remnant appears as a fibrovascular stalk emanating from the optic disc anteriorly and connecting to the posterior lens surface, resulting in a lens opacity or plaque (97, 98). The lens opacity may be quite small, or may extend all the way to the lens equator and involve the ciliary processes, which may significantly increase the risk of glaucoma. Surgical intervention is indicated if the opacity is visually significant. Eyes with PFV may also be associated with various other ocular abnormalities and are usually small. Amblyopia stemming from cataracts, high refractive errors (usually hyperopia), and glaucoma are the most common sources of visual impairment. The fibrovascular tissue may cause traction on the retina adjacent to the optic disc, leading to a traction retinal detachment. When this occurs, the visual prognosis is extremely poor.2,3