Why lab evaluation is rarely needed in pediatric cataract patients

Indianapolis-Although there is a long list of systemic disorders that can lead to pediatric cataracts, rarely does the ophthalmologist need to initiate laboratory evaluation to diagnose an underlying cause, according to Daniel E. Neely, MD.

“Be conservative and do not take a shotgun approach,” said Dr. Neely, professor of ophthalmology, Indiana University School of Medicine, Indianapolis. “About 90% of unilateral congenital or infantile cataracts are idiopathic, and while children with bilateral cataracts are much more likely to have an associated systemic disease or inheritance pattern, there is usually some other exam finding or historical evidence to suggest the correct diagnosis.

“Furthermore, systemic abnormalities do not usually present to the ophthalmologist undiagnosed or unsuspected,” he continued.

In the case of unilateral cataracts, lens morphology may establish a specific diagnosis and eliminate the need for laboratory studies, he said.

The two most common morphologies seen in unilateral cataract are persistent fetal vasculature and posterior lentiglobus. In the absence of these findings or known trauma, intrauterine infection might be considered as the etiology and evaluated by ordering a serum TOxoplasmosis, Rubella, Cytomegalovirus, Herpes simplex (TORCH) titer and Venereal Disease Research Laboratory test (VDRL) for syphilis.

“However, cataracts associated with an intrauterine infection are usually bilateral,” Dr. Neely added.

When contemplating laboratory testing in children with bilateral cataracts, clinicians should first note the family history, he said.

If there is evidence of an autosomal dominant inheritance pattern and the child is otherwise normal, laboratory evaluation is not needed. Otherwise, a TORCH titer, VDRL, and serum testing for galactose-1-phosphate uridyl-transferase-the definitive diagnostic test for galactosemia-are indicated.

Galactosemia is diagnosed in most children before cataract develops because testing for galactosemia is part of the newborn laboratory evaluation performed in every state, Dr. Neely added.

“If you suspect galactosemia, it makes sense to go straight to the definitive diagnostic test, which is a direct assay of enzyme activity in whole blood,” he explained.

Other laboratory tests that may be considered, but are likely to have low yield, include serum calcium and phosphorous for hypoparathyroidism and pseudohypoparathyroidism, respectively, and measurement of urinary amino acids to detect Lowe syndrome.

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