Outcomes of Conventional 8.0-mm Versus Large 9.0-mm Diameter Deep Anterior Lamellar Keratoplasty for Keratoconus

Purpose:The purpose of the study was to compare the clinical outcomes of large 9.0-mm diameter and conventional 8.0-mm big-bubble deep anterior lamellar keratoplasty (DALK).Methods:In this comparative, retrospective interventional case series, medical records of 124 cases of large 9.0-mm diameter DALK from January 2017 to December 2019 and 133 conventional 8.0-mm DALK from January 2014 to December 2016 performed by a single surgeon for the indication of keratoconus were reviewed. Main outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), and postoperative complication rates.Results:Postoperative logarithm of the minimum angle of resolution BSCVA did not significantly differ between 9.0-mm and 8.0-mm DALK at any time points. Although the cumulative percentage of eyes achieving Snellen BSCVA of 20/40 or better was comparable between groups (9.0-mm DALK: 93%, 8.0-mm DALK: 90%, P = 0.571), the cumulative percentage of eyes achieving 20/20 or better (9.0-mm DALK: 44%, 8.0-mm DALK: 26%, P = 0.01) and 20/25 or better (9.0-mm DALK: 74%, 8.0-mm DALK: 59%, P = 0.03) was significantly higher in the 9.0-mm DALK group. RA was significantly lower in the 9.0-mm DALK group compared with the 8.0-mm DALK group during all time points (P < 0.001). The percentage of eyes with RA less than or equal to 4.0 D was significantly lower in the 9.0-mm DALK patients (90%) compared with in 8.0-mm DALK group (72%) (P = 0.002). Postoperative complication rates were similar between groups.Conclusions:Compared with conventional 8.0-mm DALK, large 9.0-mm DALK can provide superior visual outcomes at higher levels of Snellen BSCVA and significantly lower degrees of astigmatism without an increased risk of immune rejection and graft failure.