Central islands: rate and effect on visual recovery after phototherapeutic keratectomy.

PURPOSE

To retrospectively assess the proportion of patients affected by a central island (CI) and its effect on visual recovery after phototherapeutic keratectomy (PTK).

METHODS

This retrospective study evaluated 30 eyes of 21 consecutive patients (mean age ± standard deviation, 69.6 ± 6.8 years) undergoing PTK for the treatment of band keratopathy or granular corneal dystrophy. We investigated the rate of CI formation, which was defined as a steepening area of 3 D, 1.5 mm in diameter, on each corneal videokeratograph (ATLAS 9000; Carl Zeiss Meditec), and its effect on visual recovery at 3 months and at 1 year postoperatively.

RESULTS

A CI was found in 22 of 30 eyes (73%) 3 months postoperatively and in 14 of 25 eyes (56%) 1 year postoperatively. The degree of CI was significantly correlated with the change in logMAR corrected visual acuity (Spearman correlation coefficient r = 0.445, P = 0.026). The degree of CI in eyes with band keratopathy was significantly larger than that in eyes with granular dystrophy 1 year postoperatively (Mann-Whitney test, P = 0.045). The degree of CI was not significantly correlated with the ablation depth (Spearman correlation coefficient r = 0.116, P = 0.582) or the residual corneal thickness (r = -0.235, P = 0.278).

CONCLUSIONS

CI formation was found in as many as 73 and 56% of patients 3 months and 1 year after PTK, respectively, using the VISX Star S4 excimer laser system, and significantly affected the improvement of visual acuity. The anti-CI program should be applied by the manufacturer, not only for corneal refractive surgery but also for PTK in a clinical setting.