Comparison of refractive outcomes in three corneal transplantation techniques for keratoconus.

BACKGROUND

Deep anterior lamellar keratoplasty (DALK) has a much lower incidence of immunologic reactions than penetrating keratoplasty (PK) for patients with keratoconus. However, it is unclear whether DALK is better on refractive outcomes than PK, due to its high postoperative myopia.

METHODS

We retrospectively studied the clinical records of keratoconus patients who underwent PK, DALK, or predescemetic DALK (pre-DALK, DALK with residual stroma) between June 2004 and September 2008. The main outcome measures included refractive sphere, manifest cylinder, corneal power, keratometric astigmatism, and best-corrected visual acuity (BCVA) at the latest visit and the methods of visual correction. Postoperative manifest refractions and topography data were compared at postoperative 3, 5, 7, and 9 years among the three groups. Additionally, the final BCVA and the methods of vision correction were compared.

RESULTS

A total of 172 subjects (172 eyes) screened out of 207 keratoconus patients underwent PK (79 eyes), DALK (68 eyes), or pre-DALK (25 eyes). Postoperative myopic refractive sphere increased in all groups, but the most obvious increase was noted in the pre-DALK group. At the 9-year follow-up, both the pre-DALK group (-6.5 ± 1.7 D) and DALK group (-6.1 ± 1.8 D) had higher myopic refractive sphere than the PK group (-5.0 ± 1.5 D, p < 0.05). Postoperative myopic manifest astigmatism progressively increased in 5 years, but there were no differences among the groups. The progressive increases in postoperative corneal power were recorded in all groups, with the highest one in the pre-DALK group and the lowest in the PK group. At the 9-year follow-up, both the pre-DALK (49.8 ± 2.7 D) and DALK (48.8 ± 2.1 D) groups had higher corneal power than the PK group (47.3 ± 2.0 D); meanwhile, the corneal power was higher in the pre-DALK group than the DALK group (p < 0.05). No differences were noted with respect to keratometric astigmatism among the groups. Mean LogMAR BCVA was 0.12 ± 0.12 in the DALK group, 0.17 ± 0.10 in the pre-DALK group, and 0.1 ± 0.11 in the PK group (p = 0.325) at 9 years after surgery. Moreover, the methods of achieving BCVA seem to be similar among the treatment groups.

CONCLUSIONS

Although DALK has a slightly higher degree of myopic refraction than PK, DALK and PK have comparable visual acuity outcomes and similar methods of vision correction. DALK is recommended for the treatment of keratoconus.