Abstract
Purpose: :
Rarebit perimetry (RBP) has shown promise in the early detection of optic nerve disease and neural disorders, although its reproducibility has not been fully established.
Methods: :
We compared retest variability in RBP and two types of standard automated perimetry (SAP): Humphrey 24-2 Swedish Interactive Thresholding Algorithm (SITA) testing with a Goldmann size III stimulus and Humphrey 24-2 Full Threshold testing with a Goldmann size I stimulus. Eighteen ocular healthy individuals (mean age = 44 ± 14 years) participated in the study. Test subjects were scheduled for 5 separate visits within a 5-week period. During each visit, subjects performed Size III, Size I, and RBP testing in random order.
Results: :
Coefficients of variation (CV) for each test were averaged across the 5 visits and used to compare variation by performing a 1-way ANOVA followed by a Newman Keuls post hoc test. Size I had the highest mean CV at 7.8 ± 1.8, followed by RBP at 6.1 ± 3.5, and Size III at 3.8 ± 0.44; these differences were statistically significant (P<0.0001). All three tests had a trend of increasing CV with age, but none had a slope significantly different than zero due to large amounts of variation. Thresholds were found to increase slightly with age, but Size III was the only test which revealed a statistically significant slope. Test results were found to improve slightly in consecutive trials, but the trend was not statistically significant.
Conclusions: :
While tests using smaller stimulus sizes, such as Size I and RBP, may be more sensitive for visual defects, they may also confer an increased amount of variability. This should be taken into consideration when selecting the most appropriate test for a given situation. A normative database for Rarebit perimetry would be helpful for proper clinical interpretation.
Keywords: perimetry • visual fields • clinical research methodology