COMPARISON OF PATTERN-ONSET, PATTERN-REVERSAL AND PATTERN-OFFSET VEPSIN TREATED AMBLYOPIA

Purpose There are differences in the properties of visual evoked poten tials (VEPs) to various forms of pattern stimulation and it is not cle ar how these differences reflect macular and parmacular function in am blyopic and normal eyes. We assessed pattern-onset, -reversal and -off set VEPs from amblyopic eyes and compared them with the responses from the fellow eyes, and from controls, to gauge the relative effectivene ss of these stimulus modes. Methods The three modes of pattern stimula tion were presented sequentially in a single recording run to enable d irect comparisons to be made for identical recording conditions. Half- field stimulation was used, as this elicits components over the ipsila teral and contralateral occipital scalp relative to the stimulated hal f-field, which reflect stimulation of macular and paramacular areas of the visual field. Eighteen amblyopes treated by occlusion and 20 cont rol children were studied. Results Multivariate analysis of variance s howed significant differences between ambylopic and fellow eyes in amb lyopes: pattern-onset components were significantly attenuated and ips ilateral reversal components were significantly prolonged in amblyopic eyes. When fellow eyes of amblyopes were compared with the eyes of co ntrols, the reversal P100 and offset P110 and N165 components showed s ignificant differences. Conclusions Ipsilateral reversal components an d onset CII and contralateral P105 were the most affected in amblyopic eyes. The subnormal findings for the fellow eyes of amblyopes suggest that occlusion may have a long-standing physiological effect on the p atched eye, not normally clinically apparent.