Factors Associated With Improvement in Vision Following Femtosecond Astigmatic Keratotomy in Post-Keratoplasty Keratoconus Patients

Purpose: To evaluate factors associated with improvement in vision following femtosecond astigmatic keratotomy (FSAK) in patients with keratoconus post-keratoplasty. Design: Retrospective, interventional case series. Methods: The study took place in an institutional setting. This was a retrospective study that included patients with keratoconus who underwent FSAK for astigmatism following penetrating (PKP) or deep anterior lamellar keratoplasty (DALK). Success was defined as improvement in 3 Early Treatment Diabetic Retinopathy Study lines (doubling of the visual angle) of uncorrected distance visual acuity (UDVA) or best spectacle-corrected visual acuity (BSCVA). Results: A total of 56 eyes in 56 patients with keratoconus were included. Following FSAK, there was a significant improvement in UDVA (1.30 ± 0.49 to 0.87 ± 0.58 logarithm of minimal angle of resolution [logMAR]; P < .001), BSCVA (0.40 ± 0.26 to 0.27 ± 0.29 logMAR; P <.001), and corneal astigmatism (8.69 ± 2.72 to 3.92 ± 2.13 diopter [D]; P < .001). Success was achieved in 60.7% (34/56) of cases, and this group had a higher proportion of previous PKP (73.5% vs 45.5%; P = .03), worse preoperative UDVA (1.42 ± 0.47 vs 1.11 ± 0.47 logMAR; P = .03), and a greater preoperative manifest cylinder (7.56 ± 2.26 vs 5.72 ± 2.12 D; P = .01). In multiple regression analysis, PKP (vs DALK) (odds ratio [OR]: 8.52; P = .009), worse preoperative UDVA (OR: 9.08, P = .02), and greater preoperative cylinder (OR: 1.51; P = .04) were independently associated with success, and, when combined, led to a sensitivity and specificity of 84.6% and 93.8%, respectively, in predicting success. The optimal cutoff predicting success with a preoperative cylinder was a cylinder >6.75 D. Conclusion: Approximately 60% of patients with keratoconus post-keratoplasty experience doubling of the visual angle following FSAK. Patients with previous PKP and a greater cylinder are more likely to benefit from this procedure. Separate nomograms for DALK and PKP patients may be warranted.