VISUAL FUNCTION IN HYPERMETROPIA - AN ELECTRORETINOGRAPHIC AND PSYCHOPHYSICAL STUDY

Dark-adapted retinal function was tested electroretinographically and psychophsysically in patients with severe hypermetropia. These patient s were first tested in 1982 and were classified into three electroreti nographic categories subnormal, normal and supernormal, according to t he amplitudes and the b-wave to a-wave relationships of their dark-ada pted electroretinographic responses. These patients were invited for a follow-up examination to examine whether the subnormal electroretinog ram represented a stationary or a progressive syndrome, to correlate f unctional vision to the electroretinographic findings and to determine the changes in refraction and electroretinographic responses that mig ht have occurred during an 8-year period. No significant changes were seen in the amplitudes and b-wave to a-wave relationships of the elect roretinographic responses. These observations supported the initial el ectroretinographic classification of the hypermetropic patients and in dicated that the patients belonging to the subnormal group were probab ly characterized by a stationary defect. The psychophysically determin ed thresholds at different retinal loci (from 30-degrees nasal to 40-d egrees temporal) were within the normal range for all the patients reg ardless of their electroretinographic characteristics. Thus, the abnor mal electroretinographic responses of hypermetropic patients probably did not reflect abnormal retinal function but may be accounted for by changes in the electrical resistances of extraretinal tissues relative to that of the retina itself.