Spontaneous long-term changes of corneal power and astigmatism after suture removal after penetrating keratoplasty using a regression model

PURPOSE: To assess the diagnosis,based spontaneous long-term changes in corneal power and refraction with a regression model in the all,sutures-out time period following non-mechanical penetrating keratoplasty (PK). DESIGN: Retrospective non-randomized clinical trial. METHODS. SETTING. Clinical practice. STUDY POPULATION. 147 eyes [47 Fuchs dystrophy (FD); 100 keratoconus (KC)] were studied after suture removal in this retrospective longitudinal study. MAIN OUTCOME MEASURES: Zeiss keratometry [equivalent power (KEQ) and astigmatism (KAST)], corneal topography analysis [equivalent power (TEQ) and astigmatism (TAST)], and subjective refractometry [spherical equivalent (SEQ) and refractive cylinder (RAST)] were assessed in at least three up to 16 ophthalmologic examinations in the all-sutures-out time period. OBSERVATION PROCEDURE. The time course of each target variable was analyzed in a longitudinal manner (time interval a: 12 months) separately for each patient with a linear regression model. RESULTS: Post-keratoplasty follow,up ranged from 31 months to 10.3 years. In the linear regression model, the annual change in FD/KC showed an increase/a decrease in KEQ (0.29 +/- 0.50/-0.63 +/- 0.46 diopters, P = .02) and an increase/a decrease in TEQ (0.37 +/- 0.54/-0.69 +/- 0.49 diopters, P = .04) corresponding to a decrease/an increase in SEQ (-0.31 +/- 0.47/0.63 +/- 0.43 diopters, P = .02). KAST/TAST/RAST showed a minimal annual de, crease (-0.06 +/- 0.41/-0.05 +/- 0.45/-0.06 +/- 0.41 diopters) in FD but an increase in KC (0.46 +/- 0.41/0-51 +/- 0.43/0-46 +/- 0.38 diopters) (P = .05/0.06/0.12). CONCLUSIONS: In the follow,up after post-keratoplasty suture removal, patients with FD/KC tend to develop a spontaneous myopic shift (steepening of the cornea)/hyperopic shift (flattening of the cornea). In contrast with those with FD, patients with KC should be counseled on the fact that astigmatism may increase again over time after suture removal.