Recording pattern visual evoked potentials under chloral hydrate sedation

Accurate assessment of visual function in infants and preverbal children is difficult because of the dependence on vision tests that require the patient's cooperation. In an attempt to resolve this problem, we evaluated pattern visual evoked potentials (PVEPs) obtained on infants under chloral hydrate sedation. Ten patients were studied--four with unilateral amblyopia, three with suspected amblyopia, and three without amblyopia. Patients with amblyopia showed robust and reproducible responses from the sound eye, while responses from the amblyopic eye were significantly diminished (amplitude ratio less than or equal to 0.63). The PVEP responses from patients without amblyopia were large in amplitude and symmetrical between fellow eyes (amplitude ratio greater than 0.9). In two eyes with normal vision, optically fogging the patterned stimulus image substantially reduced the PVEP response, establishing a sensitivity to pattern images rather than changes in the overall luminance. We have thus determined that the PVEP can be reliably obtained under chloral hydrate sedation and that these responses, like PVEP responses taken in the awake state, reflect the presence of amblyopia and image clarity. Use of the PVEP with chloral hydrate sedation may prove clinically useful for detecting amblyopia in uncooperative infants and children.