Impact Of Topographic Localization Of Corneal Ectasia On The Outcomes Of Deep Anterior Lamellar Keratoplasty Employing Large (9 Mm) Versus Conventional Diameter (8 Mm) Grafts

To compare visual and topographic outcomes of large (9.0 mm) versus conventional (8.0 mm) deep anterior lamellar keratoplasty (DALK) for the treatment of keratoconus (KC), in relation to the different localization of the corneal ectasia (within or beyond the central 8.0 mm).

Patients underwent DALK between June 2010 and November 2020 by the same experienced surgeon at "Magna Graecia" University of Catanzaro, Italy.

This is a retrospective, comparative case series. Preoperatively, the topographic extension of the conus was calculated by measuring the distance from the geometric center of the cornea and the outermost point of the corneal ectasia (ectasia <8.0 mm, group A; ectasia ≥8.0 mm, group B). DALK was performed using both small grafts (8.0 mm, group 1) and large grafts (9.0 mm, group 2). Best-corrected visual acuity and topographic astigmatism were evaluated preoperatively (T0) and postoperatively after complete suture removal (1 year, T1).

Data from 224 eyes of 196 patients were evaluated. Topographic astigmatism improved in the entire series at T1 (4.94±2.92 dioptres (D) [95% CI, 4.56-5.33] vs 4.19±2.45 D [95% CI, 3.87-4.51], p=0.001). There was no significant difference in postoperative topographic cylinder between group 1 and group 2 when considering eyes with corneal ectasia <8.0 mm (group 1A, 4.15±2.19 D [95% CI, 3.64-4.66]  vs group 2A, 3.65±2.13 D [95% CI, 2.92-4.38], p=0.14); conversely, the difference was significant considering eyes with corneal ectasia ≥8.0 mm (group 1B, 4.74±2.90 D [95% CI, 4.09-5.38] vs group 2B, 3.68±1.94 D [95% CI, 3.10-4.26], p=0.02).

Large 9.0-mm DALK provided better anatomical outcomes compared to conventional 8.0-mm DALK, particularly in eyes with corneal ectasia extending beyond the central 8.0 mm.