ANALYSIS OF CORNEAL TOPOGRAPHY AFTER AUTOMATED LAMELLAR KERATOPLASTY

Purpose: The purpose of the study is to evaluate the effects of myopic automated lamellar keratoplasty (ALK) on corneal topography. Methods: The authors performed a retrospective study of computer-assisted topo graphic maps obtained before surgery and at the last follow-up visit o f 9 patients (13 eyes) who underwent ALK without enhancement to correc t moderate-to-high myopia during a 12-month period. Results: Follow-up ranged from 3.5 to 13 months (mean, 5.8; standard deviation, 3.1). Th e mean manifest spherical equivalent changed from -10.5 +/- 2.2 diopte rs (D) before surgery to -1.1 +/- 1.8 D al the last follow-up visit. M ean simulated keratometry (Sim K) decreased from 45.6 +/- 1.9 D to 38. 9 +/- 2.7 D. Mean corneal astigmatism increased from 1.3 +/- 0.8 D to 2.1 +/- 0.9 D. The mean surgically induced cylinder vector (calculated by vector analysis) was 1.1 +/- 0.6 D, Mean surface regularity index (SRI) and surface asymmetry index (SAI) increased from 0.37 +/- 0.38 a nd 0.32 +/- 0.43 before surgery to 1.00 +/- 0.32 (P < 0.001) and 0.75 +/- 0.36 (P = 0.01), respectively, at the last visit. A positive corre lation was observed between the decrease in mean Sim K and ?he increas e in manifest spherical equivalent (reduction of myopia) (r = 0.77, P = 0.002), increase in SRI (r = 0.73, P = 0.005), and increase in SAI ( r = 0.58, P = 0.04). The change in manifest spherical equivalent was s ignificantly less than the change in Sim K (P < 0.001). Conclusions: M yopic ALK significantly flattens the cornea and reduces myopia. Howeve r, it induces corneal astigmatism and decreases corneal surface regula rity and symmetry. The degree of myopic correction, as well as the sur gically induced corneal surface irregularity and asymmetry, is positiv ely correlated with the amount of corneal flattening derived from the surgical procedure.