Effect of Laser in situ Keratomileusis on Tear Secretion and Corneal Sensitivity

PURPOSE: To study changes in corneal sensitivity and Schirmer I scores following laser in situ keratomileusis (LASIK) and the correlation between the two. METHODS: Twenty-three patients who had LASIK at The Gimbel Eye Center, Toronto, Ontario, Canada, participated in the study. All were asymptomatic for severe dry eyes before surgery. All patients underwent a Schirmer test (without anesthetic), a filament corneal sensitivity test, and slit-lamp microscopy including staining with lissamine green preoperatively and at postoperative time intervals of 3 to 5 days, and 1 and 3 months. RESULTS: No correlation was found between the difference in Schirmer test scores and the difference in corneal sensitivity, at any timepoint. A non-statistically significant trend toward a reduction in Schirmer values immediately after surgery was noted, with a return to slightly lower than baseline levels by 3 months. Corneal sensitivity was significantly decreased immediately after surgery and returned to preoperative levels by 3 months (P<.0001). There was a statistically significant effect of age, gender, and mean spherical equivalent refraction on corneal sensitivity (P<.0001) and a significant effect of age on the time trend (P=.02), but not for Schirmer levels or staining. CONCLUSIONS: A significant reduction in corneal sensitivity immediately following surgery occurred, with a return to preoperative levels by 3 months. Schirmer test scores similarly decreased, although without statistical significance, and returned to near preoperative levels after 3 months. A statistically significant correlation between the reduction in tearing and reduction in corneal sensitivity after LASIK was not demonstrated.