Measuring vision in refractive surgery.

After years of inventing, evaluating, and perfecting refractive surgical procedures, the future focus will be on the “quality of vision” after surgical interventions. The number of surgical procedures to correct refractive errors is steadily increasing, older procedures are being replaced by newer ones, the complication rate is decreasing, and the results of each established procedure are improving with more experience, better technology, and scientific evaluation. The success or failure of refractive procedures, defined by criteria such as safety, efficacy, stability, and predictability, is based on Snellen acuity. However, some patients who present with anatomically perfect results and excellent visual outcome with respect to these criteria complain of visual disturbances such as decreased contrast, unusual color perception, glare, halos, or simply “bad vision.” In some cases, we can explain the problem; eg, residual astigmatism or a discrepancy between the scotopic pupil diameter and the corneal ablation zone in myopic excimer surgery. In some cases, we cannot find an answer. And in some cases, we see retrospectively that there should have been problems (6.0 mm ablation zone for laser in situ keratomileusis [LASIK] and a 7.0 mm scotopic pupil size) that fortunately did not occur. Determining the outcome is a complex process. Why do only some patients complain? Are some complaints associated with residual refractive error? Do we increase aberrations with our interventions? Is avoiding eyes with large pupils a guarantee for avoiding visual disturbances? Which refractive procedure is best suited to a specific patient and a specific refractive error regarding quality of vision? Snellen acuity alone will not be sufficient to determine the quality of vision for refractive procedures, as emphasized in a recent editorial.