The Contribution of the Posterior Surface to the Corneal Aberrations in Eyes after Keratoplasty

Abstract

To investigate the contribution of posterior corneal surfaces to higher-order aberrations (HOAs) of the cornea, optical quality, and visual acuity after keratoplasty. Corneal topography of anterior and posterior surfaces and pachymetry were conducted using anterior segment optical coherence tomography (AS-OCT) in 40 eyes (10 eyes after penetrating keratoplasty [PK], 10 eyes after deep anterior lamellar keratoplasty [DALK], 10 eyes after Descemet's stripping automated endothelial keratoplasty [DSAEK], and 10 normal eyes). Anterior, posterior, and total corneal HOAs were calculated using ray-tracing and decomposition into Zernike polynomials and were evaluated as root mean square values. Modulation transfer functions (MTFs) were also evaluated. Topography maps of the anterior and posterior surfaces showed reverse patterns in the normal, PK, and DALK eyes, but not in DSAEK eyes. In the normal, PK, and DALK eyes, the total corneal HOAs were significantly smaller (~10%) than were the HOAs of the anterior surface (P < 0.01), whereas there was no significant difference between total and anterior HOAs in the DSAEK eyes (P = 0.483). In the normal, PK, and DALK eyes, the MTFs of the total cornea were slightly better than those of the anterior surface. In the DSAEK eyes, the MTFs of the total cornea were lower than those of the anterior surface. Visual acuity was significantly correlated with total and anterior surface HOAs (P < 0.05). Posterior surfaces compensate for anterior aberrations in normal, PK, and DALK eyes. In DSAEK eyes, the posterior surface increased total corneal HOAs and had a negative influence on MTFs.