Retinal nerve fiber layer thickness in human strabismic amblyopia

BACKGROUND AND PURPOSE: Amblyopia is characterized by histopathological changes in the visual cortex and lateral geniculate nucleus. In the retina, however, no abnormalities have yet been reported. The purpose of this study was to compare the nerve fiber layer (NFL) thickness in the amblyopic eye with that in the sound eye of patients with strabismic amblyopia. As a practical implication, we investigated the validity of comparing Nerve Fiber Analyzer (NFA) measurements obtained in amblyopic eyes to the normative database built into the NFA.

METHODS: NFL thickness was measured with a third generation NFA, the GDx (Laser Diagnostic Technologies, San Diego, CA). This is a scanning laser polarimeter, designed for monitoring glaucoma. The following NFL thickness parameters (all in microns) were compared: average thickness, superior maximum, inferior maximum, superior average, inferior average, nasal median and temporal median. Twenty patients with strabismic amblyopia were imaged with the NFA. Patients had no nystagmus, neurological disease or glaucoma. Nine patients had amblyopia in the right eye, and 11 patients in the left eye.

RESULTS: In general, the sound eyes yielded higher thickness measures than the amblyopic eyes. These differences, however, were small, averaging only 1.5%, p = 0.6, and therefore not "statistically significant" at the p&le 0.05 level.

CONCLUSIONS: Using the standard of "Statistical Significance = p< or =0.05", when amblyopic eyes are measured with the NFA, the built-in normative database may serve as the reference data