• Cornea/External Disease

    This retrospective, case-control study investigated the magnitude of anterior and posterior corneal higher-order aberrations (HOAs) in eyes that underwent corneal transplantation by PK, DALK or DSAEK. Anterior corneal HOAs were significantly lower in DSAEK eyes than PK or DALK eyes, but posterior corneal HOAs were similar between the groups.

    The mean posterior corneal surface total HOAs in the PK (24 eyes), DALK (28 eyes), DSAEK (19 eyes) and control groups were 0.20 ± 0.09 μm, 0.24 ± 0.11 μm, 0.27 ± 0.15 μm and 0.07 ± 0.02 μm, respectively. The mean anterior corneal surface total HOAs in the PK, DALK, DSAEK and control groups were 1.38 ± 0.67 μm, 1.19 ± 0.57 μm, 0.61 ± 0.33 μm and 0.21 ± 0.07 μm, respectively. Anterior corneal HOAs were significantly lower in the DSAEK group than in the PK (P < 0.001) and DALK groups (P < 0.001), but they were similar between the DALK and PK groups. Control eyes had significantly lower total HOAs than DSAEK eyes in both the anterior and posterior surfaces, which likely is due to the difference in the background bullous keratopathy.

    Another interesting finding, the authors note, was that most of the anterior-to-posterior (A/P) corneal HOA ratios were 3 or 4 in the DSAEK and control eyes, compared to 5 to 7 in PK and DALK eyes. Moreover, the A/P ratio of coma was markedly greater than those of the total HOAs in PK and DALK eyes, although this tendency was not found in control and DSAEK eyes. This suggests that the contribution of an irregular anterior corneal surface resulting from the host–graft junction may be more enhanced in PK and DALK eyes than in DSAEK eyes because of the difference in the refractive indices on the anterior and posterior surfaces.

    The authors conclude that, especially now that DSAEK has gained popularity as a transplantation procedure, it is important to evaluate the optical properties of both the anterior and posterior surfaces. A prospective investigation comparing DALK or DSAEK with PK is needed to clarify the optical characteristics of each procedure associated with the position of the donor corneas.