JUL 15, 2011
Although patient satisfaction after refractive surgery is high in the general population, glare problems are frequent. However, glare sensitivity must be normal for the most demanding professions because glare can affect the velocity of execution of visually guided tasks. This study evaluated the use of straylight testing to screen for ocular fitness after refractive surgery in demanding professions.
Investigators analyzed data from routine medical fitness examinations given at an independent military institute that used the commercially available C-Quant instrument with the psychophysical compensation comparison (CC) method to measure intraocular straylight. A refractive surgery population of 198 subjects (373 eyes) was compared to a reference population of 214 young individuals (mean age, 21 years; 402 eyes) without a history of refractive surgery. To evaluate methodological aspects, investigators also compared the fellow eyes of the refractive surgery population. The prevalence of impairment was evaluated for two age-independent cutoff criteria, a 2.0-fold and 3.2-fold increase, and an age-dependent cutoff criterion corresponding to an increase of 0.20 log units.
The CC method exhibited good repeatability with low chances of impaired scores due to measurement variability. The prevalence of impaired straylight values was minimal in the reference population. In the refractive population, 9 percent of values were above the factor 2.0 criterion, 2 percent were above the factor 3.2 criterion, and 12 percent were 0.20 log units above the age reference.
The authors note that prior research studies have found a smaller increase in straylight values in patients who had undergone refractive surgery. However, this is probably because the post-refractive surgery patients in this study were treated in clinical centers unrelated to the testing center, which resulted in a more general estimation of the prevalence of impaired straylight values.
Based on these results, the authors recommend a factor of 2.0 above normal straylight levels as the cutoff between normal and impaired values for demanding professions. The application of this criterion in the present refractive population would result in a 4 percent disqualification rate.