Impact of cone base diameter on outcomes of deep anterior lamellar keratoplasty in keratoconus

Purpose To evaluate the outcomes of deep anterior lamellar keratoplasty (DALK) in treating keratoconus in relation to cone base diameter (CBD). Methods A retrospective study. Sixty-one eyes of 49 keratoconus patients who underwent DALK between 2009 and 2018 were enrolled. Preoperative and postoperative uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), spherical equivalent, and astigmatism were measured. Scheimpflug tomography (Pentacam) was used to measure the cone base area (CBA) and CBD using MATLAB software. Results The mean age of the patients was 20.8 +/- 6.1 years old, and the mean follow-up time was 27.3 +/- 15.2 months. Mean UCVA improved from 1.23 +/- 0.48 to 0.57 +/- 0.27 (LogMAR, 95% CI [0.52, 0.80]; P < 0.001), whereas mean BCVA improved from 0.98 +/- 0.55 to 0.18 +/- 0.13 (95% CI [0.66, 0.94]; P <0.001). The mean spherical equivalent decreased by 4.53 +/- 5.65 D (95% CI [- 6.25, - 2.82]; P < 0.001), with little change in astigmatism (95% CI [- 1.39, 0.64]; P = 0.457). The postoperative BCVA in the patients with CBD < 5.07 mm and corneal curvature >= 55D was significantly better than those whose CBD >= 5.07 mm (0 14 +/- 0.09 vs 0.25 +/- 0.15, P = 0.001). The follow-up time was negatively correlated with the BCVA (P = 0.004). Conclusions In this study, outcomes of DALK in keratoconus were related to CBD and corneal curvature. Patients with large CBD (>= 5.07 mm) where the corneal curvature >= 55D are more likely to have poor visual outcomes after DALK.