Persistence of diurnal fluctuation after radial keratotomy

Three patients were examined before 8:00 AM and after 7:00 PM to determine diurnal changes in uncorrected visual acuity, refractive error, and average central keratometric power at 3 months, 4 years, and 6 years after radial keratotomy. The average absolute diurnal change in the spherical equivalent refraction increased over time: 0.26 diopters at 3 months, 0.75 D at 4 years, and 1.29 D at 6 years. Diurnal change in the absolute average keratometric values were not progressive: 0.35 D at 3 months, 0.27 D at 4 months, and 0.40 D at 6 years. Computer-assisted corneal topographic analysis demonstrated diurnal changes in the topography that may be subtle and not necessarily reflected in the average keratometry values. These limited data suggest that wound healing over several years may not restore stability to the cornea.