A simple grating visual acuity test for impaired children

Twenty-five developmentally delayed or neurologically impaired nonverbal children, aged 2 to 15 years, referred for visual acuity assessment, were beyond the age at which standard preferential-looking techniques are considered to be effective and none could be tested with Snellen letters, illiterate Es, or Allen pictures. Our method, in which the children learn to point to grating stimuli, enabled us to obtain monocular visual acuity estimates in 19 of the 25 patients. When indicated, patching therapy was begun and was monitored with this method. Similar testing of 31 unimpaired children showed good prediction of recognition visual acuities except in patients with visual acuities worse than 20/160. The grating method accurately identified or excluded amblyopia in 26 of 31 children (84%). We consider this a clinically useful test of visual acuity in nonverbal impaired children.