CHARACTERISTICS OF CORNEAL STAINING IN HYDROGEL CONTACT-LENS WEARERS

Corneal fluorescein staining is widely used in clinical practice and r esearch, but little information exists on the distribution of staining in a large group of asymptomatic contact lens wearers. This cross-sec tional study took place at 3 centers, and investigated the pattern of corneal fluorescein staining in both eyes of 98 hydrogel contact lens wearers. We also investigated the strategies used by three experienced clinicians to grade corneal staining. Overall corneal staining was gr aded using a scale from 0 to 4 in one-half steps, and five corneal zon es, superior, inferior, nasal, temporal, and central, were also graded . The average overall staining grade for both eyes of our subjects was 0.50, with an average of 0.57 for the right eye and 0.44 for the left . This difference between the eyes was statistically significant (p = 0.011). In addition, a comparison of the zones within each eye showed a significant difference (p = 0.0001) among the zones. Corneal stainin g between the two eyes was also positively and significantly correlate d (r = 0.58; p = 0.0001). Grading strategies among clinical investigat ors were significantly different (p = 0.0001), indicating a potential source of bias in multi-centered studies. The difference in corneal st aining between the eyes may represent a source of systematic bias, and could be due to grading the right eye before the left. The correlatio n in corneal staining between the eyes indicates that the two eyes of a subject cannot serve as independent data points. One-third of the su bjects who participated in this study had notable corneal staining. Th is finding underlines the importance of regularly checking corneal sta ining in clinical practice.