Quality of vision and graft thickness in deep anterior lamellar and penetrating corneal allografts

PURPOSE: To compare visual function after deep anterior lamellar keratoplasty (DALK) with visual function after penetrating keratoplasty (PK) for keratoconus and correlate this with corneal thickness. DESIGN: Retrospective case series. METHODS: Twenty-three patients (32 eyes) with unilateral or bilateral DALK or PK for keratoconus were analyzed for visual quality after suture removal. Evaluation included measurement of visual acuity, contrast sensitivity, and higher order aberrations (HOAs) (WaveScan; Visx, Santa Clara, California, USA). Readings were performed with both spectacle and rigid contact lens correction of refractive error. Total and residual stromal thickness after DALK was measured using optical coherence tomography (OCT) and correlated to visual quality. RESULTS: Eyes after PK had better visual acuity than eyes after DALK (P = .018). Subgroup analysis of DALK eyes revealed that the level of visual acuity was related to the thickness of residual recipient corneal stroma. Eyes with a recipient corneal bed thickness of <20 microm had visual acuities similar to eyes with a PK, whereas those with a recipient thickness of >80 microm had a significantly reduced visual acuity (P = .0009). Contrast sensitivity was similar in DALK and PK eyes. There was no significant difference in HOAs between eyes with DALK or PK. CONCLUSIONS: These data suggest that the main parameter for good visual function after DALK for keratoconus is the thickness of residual recipient stromal bed. An eye with a DALK with a residual bed of <20 microm can achieve a similar visual result as a PK.