The mere presence of a cataract does not suggest that surgical removal is necessary. That determination requires assessment of the visual significance of the lens opacity.
In healthy infants aged 2 months or younger, the fixation reflex may not be fully developed; thus, its absence in this group of patients is not necessarily abnormal. In general, anterior capsule opacities are not visually significant unless they occlude the entire pupil. Central or posterior lens opacities of sufficient density that are greater than 3 mm in diameter are usually visually significant. Opacities that have a large area of surrounding normal red reflex or that have clear areas within them may allow good visual development. Strabismus associated with a unilateral cataract and nystagmus associated with bilateral cataracts indicate that the opacities are visually significant. Although these signs may also indicate that the optimal time for treatment has passed, cataract surgery may still improve visual function.
In preverbal children older than 2 months, standard clinical assessment of fixation behavior, fixation preference, and objection to occlusion provide additional evidence of the visual significance of the cataract(s). For bilateral cataracts, assessment of the child’s visual behavior and the family’s observations of the child at home help determine the level of visual function. Preferential looking tests and visual evoked potentials can provide quantitative information (see Chapter 1). In older children, particularly those with lamellar or posterior subcapsular cataracts, glare testing may be useful for assessing decreased vision.
Slit-lamp examination can help classify the morphology of the cataract and reveal associated abnormalities of the anterior segment. If the cataract allows some view of the posterior segment, the optic nerve and fovea should be examined. If no such view is possible, B-scan ultrasonography should be performed to assess for anatomical abnormalities of the posterior segment. The presence of retinal or optic nerve abnormalities cannot be definitively ruled out, however, until the posterior pole can be visualized directly. See Table 23-3 for additional information.
Unilateral cataracts are not usually associated with systemic disease; laboratory tests are therefore not warranted in these cases. In contrast, bilateral cataracts are associated with many metabolic or other systemic diseases. If the child has a positive family history of isolated congenital or childhood cataract or if examination of the parents shows lens opacities (and there are no associated systemic diseases to explain their cataracts), systemic evaluation and laboratory tests are not necessary. A basic laboratory evaluation for bilateral cataracts of unknown etiology is outlined in Table 23-3.
Further workup should be directed by the presence of other systemic abnormalities. Evaluation by a geneticist may be helpful for determining whether there are associated disorders and for counseling the patient’s family regarding recurrence risks. Next-generation gene sequencing, which analyzes large portions of the genome, is of increasing utility, even in cases without evidence of systemic disease.
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.