Long-term Changes of Corneal Power and Astigmatism after Suture Removal Following Non-mechanical Penetrating Keratoplasty Using a Regression Model
Langenbucher A., Seitz B., Naumann G. O. H.
Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen
Purpose: To assess the diagnosis-based long-term changes in keratometry, corneal topography and refraction with a regression model after suture removal following nonmechanical penetrating keratoplasty (PK).
Method: Out of a total of 1360 PKs performed with the excimer laser since 1989 we studied 69 eyes (28 Fuchs' dystrophy (D1), graft diameter 7.5 mm; 41 keratoconus (D2); graft diameter 8.0 mm; double running suture, suture removal 19±7 months after PK) in this prospective longitudinal study. Zeiss keratometry (keratometric equivalent power (KEQ) and astigmatism (KAST)), corneal topography analysis (topographic equivalent power (TEQ) and astigmatism (TEQ)) and subjective refraction (spherical equivalent (SEQ) and refractive cylinder (RAST)) were assessed within a time interval of at least 12 months after suture removal (follow-up) and with at least 3 valid all-suture-out measurements. The time course of the target variables was analyzed in a longitudinal manner with a linear regression model (minimizing the residuum between observed and predicted target variable).
Results: The follow-up interval ranged between 14 months and 7.2 years. Overall, the target variables changed on average: RAST: 3.41 to 2.21 D, KAST: 3.68 to 3.21 D, TAST 3.79 to 3.55 D, SEQ:-1.70 to 2.33 D, KEQ: 42.89 to 44.22 D, TAEQ: 44.11 t
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