AIM: To observe the values and changing rules of angle Kappa in corneal refractive surgery under light and dark conditions.

METHODS:Two hundred and thirty-four eyes of 118 patients for corneal refractive surgery were enrolled for this study. Pupil diameters and angle Kappa values under light and dark conditions were measured by Keratron Scout corneal topography.

RESULTS: There were significant differences in pupil diameters between light and dark conditions(P<0.01). More angle Kappa of both eyes distributed in the superior nasal quadrant under light conditions, and more angle Kappa distributed in the superior temporal quadrant under dark conditions. The differences of horizontal and vertical offsets of angle Kappa under two conditions were statistically significant(P<0.01).

CONCLUSION: The changes of pupil diameters in light and dark conditions could affect angle Kappa and then affect the accuracy of corneal refractive surgery centered on angle Kappa.