AN IMPROVED METHOD OF DENSITOMETRY OF RED-FREE RETINAL NERVE-FIBER LAYER PHOTOGRAPHS

The red-free negatives of 53 right eyes (30 normal eyes and 23 glaucom atous eyes) and 51 left eyes (32 normal eyes and 19 glaucomatous eyes) were analysed using two different image densitometry techniques. The first technique measured the density from rectangular sample areas, wh ile the second measured density from sector-shaped sample areas which more closely follow the course of the nerve fibres in the retina. Indi ces which measured the deviation of the data from a clinically determi ned normal 'gold standard' were calculated, and were used to determine the optimum sensitivity and specificity in separating normal from gla ucomatous eyes. There is a significant difference between the data fro m the normal and glaucomatous groups of eyes, when measured from the s ector sample areas. The relative efficacy of this technique is also sh own by the improved values of sensitivity (from 42%-70% to 70%-91%), a lthough specificity remained fairly constant (from 66%-83% to 62%-88%) .