Analysis of visual fields following excimer laser PRK

Purpose: We report the results of a prospective study that evaluated the effects of photorefractive keratectomy (PRK) on static visual field tests. Methods: The Humphrey Analyzer 81-Point Screening Tests were given to 103 patients preoperatively and then one and two years after PRK. After exclusion criteria were met, the number of eligible patients for the one year study was 75 and for the two year study, the number of patients was 45. The fields were compared regarding the 1) points missed in the central (<30°) or peripheral (>30°) field, and 2) central or peripheral estimates of sensitivity (C/PECS). T-tests and Wilcoxon Rank Sum tests assessed the association between change in sensitivity and pupil diameter, optical zone size, and attempted diopters of correction. A correlation coefficient was calculated for an association between change in sensitivity and haze. Results: PRK did not appear to affect points missed on static perimetry. Estimates of differential light sensitivity (threshold) were statistically decreased centrally and approached significance peripherally two years after PRK. However, these decreased estimates were no specifically associated with changes in optical zone size or anterior stromal haze. There may be interface related changes in some patients as evidenced by two patients with circular patterns of visual field defects. Conclusions: The clinical significance of these subtle decreases in central threshold estimates remains unknown; it is possible that a study using threshold testing may better assess the effects of PRK on estimates of sensitivity. PRK did not appear to grossly affect visual field performance as analyzed by the Humphrey 81-Point Screening Test.