STATISTICAL ASPECTS OF THE NORMAL VISUAL-FIELD IN SHORT-WAVELENGTH AUTOMATED PERIMETRY

PURPOSE. To determine the intraindividual and interindividual characte ristics of normal sensitivity derived by short-wavelength automated pe rimetry (SWAP) as a function of threshold algorithm. To determine also the influence of ocular media absorption on the magnitude of the inte rindividual variation in normal sensitivity, and hence the confidence limits, derived by SWAP. METHODS. The sample comprised 51 normal subje cts, stratified for age by decade (mean age, 55.5 years; range, 24-83 years) and experienced in white-on-white (W-W) perimetry and SWAP. One randomly assigned eye of each subject was examined on three occasions with Program 30-2 of the 640 Humphrey Field Analyzer using the Full T hreshold and FASTPAC strategies for SWAP and W-W perimetries. Ocular m edia absorption (OMA) was assessed by the difference in scotopic sensi tivity to stimuli of 410 and 560 nm. RESULTS. The group mean examinati on time (P < 0.001) was greater far SWAP than for W-W perimetry for bo th the Full Threshold (15.0% longer) and FASTPAC strategies (16.8% lon ger). The gradient of the age-decline in Mean Sensitivity for SWAP was approximately 25% less steep when corrected for OMA than when uncorre cted. The interindividual normal variability, expressed as the coeffic ient of variation, for SWAP without correction for OMA was 2.7 times g reater (range 2.0-3.9), and with correction 1.9 times greater (range 1 .4-2.9), than that for W-W perimetry. CONCLUSIONS. The increased inter individual normal variability of SWAP, exacerbated by the lack of corr ection for OMA, currently limits the utility of SWAP in that the reduc tion in sensitivity required to indicate abnormality was proportionate ly greater than for W-W perimetry.