Electrophysiologic testing of visual functions for vitrectomy candidates. I. Results in eyes with known fundus diseases.

A combination of various electrophysiologic tests--simultaneous recording of VER and ERG, EER, and single-flash ERG--is proposed to assess visual function in eyes being considered for vitrectomy. To establish the validity of the method, eyes of normal subjects and of some patients with clear media and types of ocular pathology often associated with opaque vitreous were tested. A higher stimulus threshold for VER than for ERG recorded simultaneously can be used to diagnose severe optic atrophy in eyes with opaque media. EER reflected the status of the retinal circulation and the function of the optic nerve, rather than the extent of the tractional retinal detachment in diabetic retinopathy. As electrical stimulation to the retina is little affected by opaque media, the EER can be a useful test in massive vitreous hemorrhage, diabetic retinopathy, and rhegmatogenous retinal detachment. Single-flash ERG was compared with ERG recorded with the response-summation technique. The b/a wave amplitude ratio in single-flash ERG was useful in assessing the middle layer of the retina in opaque media, whereas the latter technique, though useful when recorded simultaneously with VER, distorts the shape of the responses in such a way as to simulate the findings in retinal ischemia.