Purpose: To evaluate the threshold values of short-wavelength-sensitive (SWS, or S-cone pathways) mechanisms, throughout the 30 degrees central visual field, in a glaucoma suspect population, and to compare the results with those obtained in the Retinal Nerve Fiber Layer study.
Methods: We studied the central visual field from 288 eyes of 211 subjects classified as ocular hypertensives (160 eyes) or age-matched normal controls (128 eyes). A modified Humphrey Field Analyser was used to isolate and measure the sensitivity of the SWS mechanisms. Monochromatic red-free photographs (RNFL) were taken with a wideangle fundus camera at the same period.
Results: Comparing normal and OHT eyes, we found significant differences in sensitivity for SWS cone pathways in the superior and inferior nasal quadrants, paracentral and peripheral region, and in the superior hemifield (p<0.05). Based on the perimetric criteria described, the SWAP was pathological in 57 cases. which represents 35.6% of the total sample. Using RNFL as early glaucoma diagnostic criterion, SWAP sensitivity and specificity values were 62% and a 89% respectively.
Conclusions: SWAP is a useful test for the early detection of visual field losses. It is more sensitive than, standard automated perimetry and gives a high correlation with RNFL assessment, which has proved capable of detecting signs of glaucomatous damage several years before the onset of the typical visual field defects.