Preferential looking grating acuities of infants at risk of amblyopia.

Preferential looking (PL) has been successful in the assessment of visual acuity of infants with eye disorders that place them at risk of amblyopia, such as non-alternating strabismus, anisometropia, and complete unilateral cataracts. However, PL acuities do not always conform to clinical expectations. In most esotropic infants, even untreated esotropes with a strong fixation preference, differences in acuity between eyes are minimal. PL interocular acuity differences are marked, however, in optically corrected, severe anisometropia and, after surgery and with contact lens in place, in unilateral cataracts. A different neural basis for infant PL acuities in strabismic amblyopia vs. anisometropic and stimulus deprivation amblyopia is proposed based on the dominance of extrafoveal neural elements in detecting PL grating stimuli.