Baseline Corneal Eccentricity as a Predictor for Refractive Error Change in Overnight Orthokeratology: Results from the LOOK Study

Abstract

Abstract: : Purpose: Predicting success for an individual patient undergoing ortho-k remains a clinical challenge. Some studies have reported that the amount of baseline corneal eccentricity is a predictive factor for change in refraction attainable, while others have not found this relationship. This relationship is evaluated using data from the Lenses and Overnight Orthokeratology (LOOK) study. Methods: Data for 39 right eyes and 38 left eyes were evaluated; this includes patients who were and were not successfully treated. Subjects were examined at time of lens removal (AM visits) and 6 hours after lens removal (PM visits). Corneal topography, LogMAR VA, refraction, and slit-lamp exam were performed at each visit. Linear regression analysis was performed to determine if there was a relationship between baseline eccentricity values and the amount of refractive error change attained. Results: Mean SEQ refractive error was –2.00 +/-0.92 OD and –2.07 +/-0.82 OS; mean baseline e-value was 0.41+/-0.14 OD and 0.43+/-0.12 OS. Mean SEQ change in refraction was +2.08+/-1.10 OD and +2.16+/-1.16 OS. Linear regression analysis showed no significant relationship between baseline eccentricity and amount of SEQ refraction change when baseline SEQ was controlled for (adjusted r-square 0.41 OD, p=0.086; 0.46 OS, p=0.162). Conclusions: While some studies have found a predictive value for baseline eccentricity values, these findings do not support that hypothesis. This could be caused by a variety of factors, including different methods and algorithms used by topographers to measure eccentricity data.

Keywords: contact lens • cornea: clinical science • topography