CLASSIFICATION OF CORNEAL TOPOGRAPHY AFTER PENETRATING KERATOPLASTY

Background: Semiquantitative classification of corneal topography afte r penetrating keratoplasty has the potential for focusing information about the areal dioptric power of the cornea. The purpose of this stud y was to objectify the procedure of manual semiquantitative classifica tion using a Fourier transform of corneal topography power data and to correlate both methods. Patients and methods: Fifty patients each (30 keratoconus, 20 Fuchs dystrophy) under went nonmechanical trephinatio n (excimer laser MEL60, Aesculap-Meditec, Jena) in penetrating keratop lasty. All procedures (7.5-mm trephination diameter in Fuchs, 8.0 mm i n keratoconus, double-running 10-0 nylon suture) were done by one surg eon. Pre-, intra- and postoperative treatment were identical. At the f ollow-up examinations, the keratometric astigmatism, qualitative and q uantitative criteria of the automatic videokeratography, visual acuity and refraction were assessed. Corneal topography was classified both manually and based on Fourier coefficients. Results: After a mean foll ow-up of 24 +/- 5 months, keratometric net astigmatism was 3.0 and 2.7 D with keratoconus and Fuchs dystrophy. Corneal topography analysis s howed a higher orthogonality of the bowtie shape and less asymmetry be tween opposite hemimeridians with increasing follow-up after keratopla sty. The semiquantitative classification showed a statistically signif icant correlation with the classification based on Fourier coefficient s, especially with higher astigmatism and after suture removal (P = 0. 04/0.01 before/after suture removal). Discussion: After nonmechanical trephination, the semiquantitative classification of corneal topograph y can be synthetized using Fourier analysis of corneal dioptric power data. In the future, this method may be favored for prediction of pote ntial best-corrected visual acuity after penetrating keratoplasty.