Abstract
Clinical investigations of intraocular lenses are guided by ISO and ANSI standards, which outline parameters for procedures such as contrast sensitivity (CS). The effect of glare on CS is often studied, however is not standardized. ISO/ANSI recommend a level of glare that reduces mesopic CS by 0.1 log units at 6 cpd, determined through a small pilot study, however this ambiguous criterion might result in varying glare intensities across manufacturers.
Healthy young adults (<40 yrs.), with VA of at least 20/20 were enrolled. Mesopic CS at 6 cpd was measured with and without glare in 39 subjects using the Clinical Trial Suite (CTS, M&S Technologies) and in 20 subjects using the CSV-1000 (Vector Vision) at 2.5 meters. Glare strength was set as standard for both devices (CTS:150 lux; CSV:12 lux, both before a 1.5 ND filter). Two attenuated glare levels (69 and 110 lux) were also evaluated with the CTS.
The mean decrease in CS under standard glare strength was 0.16log units for CTS (95% CI 0.05, n=29) and 0.09log units (95% CI 0.08, n=12) for CSV. Under attenuated glare, the decrease in CS measured with the CTS was 0.14 (95% CI 0.06, n=20) and 0.15 (95% CI 0.05, n=24) log units for 69 and 110 lux, respectively, both above 0.1 log unit criteria.
These results suggest that different criteria were used to calibrate glare strength of both systems, which resulted in ~12 fold difference in strength. Subsequently, clinical data obtained may not be comparable across these systems.