Effects of laser-induced retinal lesions on perimetric thresholds

Differential light sensitivity and high-pass resolution thresholds were studied before and after pan-retinal photocoagulation in subjects with proliferative diabetic retinopathy. The photocoagulated retinal area was measured and the relative change in ganglion cell separation was estimated. The change in differential light thresholds after treatment, when expressed in decibels, appeared to be linearly related to the calculated change in ganglion cell separation. At present, this empirical finding lacks a theoretical explanation. For high-pass resolution, theory predicts a direct proportionality between the change in ganglion cell separation and resolution threshold. This relationship was confirmed, supporting the claim that high-pass resolution directly reflects the number of functional retino-cortical neural channels.