[Long-term outcome after penetrating keratoplasty for keratoconus--impact of preoperative corneal curvature and best corrected visual acuity on the functional results].

BACKGROUND

The purpose of this study was to assess the long-term functional visual results of penetrating keratoplasty for keratoconus and to assess the impact of the patient's preoperative corneal curvature and preoperative best spectacle corrected visual acuity (BCVA) on the refractive outcome.

PATIENTS/MATERIAL AND METHODS: In this retrospective study 456 patients with keratoconus who received central round penetrating keratoplasty (PK) were examined 1/3/5/8/ > 9 years postoperatively. Patients were divided retrospectively into subgroups: first based on their preoperative keratometric (K-) readings: group I.1, < 50 diopters (D) (n = 21); group I.2, 50 - 60 D (n = 102); group I.3, > or = 60 D (n = 164); group I.4, irregular corneal shape with non-measurable K-reading (n = 158), group I.0 unknown preoperative K-reading (n = 58) and then based on the preoperative BCVA: group II.0 BCVA < or = 0.1 (n = 204); group II.1 BCVA > 0.1 (n = 263). The trephination was performed using the 193-nm excimer laser and the transplanted cornea was fixed by a double running cross-stitch suture. The outcome measures included keratometric central refractive equivalent (KEQ), keratometric astigmatism (AST), spherical equivalent (SEQ), refractive cylinder (CYL), best corrected visual acuity (BCVA), surface regularity index (SRI), surface asymmetry index (SAI)topographic central power equivalent (T-EQ) and topographic astigmatism (T-AST).

RESULTS

Five/eight years postoperatively, BCVA was 0.71/0.73; KEQ was 43.4/44.4 D; SEQ -1.6/-0.8; AST was 3.4/3.6 D; CYL was 3.0/3.0 D, SRI was 0.88/0.83; SAI was 0.78 / 0.78; T-EQ was 44.5/44.9 D and T-AST was 4.0/4.2 D. The results for BCVA of patients whose preoperative BCVA measured < or = 0.1 were significantly worse than the results of patients with better preoperative BCVA. Other comparisons among the subgroups revealed no further significant differences for any parameter tested.

CONCLUSIONS

In our study the long-term results of BCVA after penetrating keratoplasty for keratoconus seem to be quite stable (0.7). This indicates that corneal transplantation is a viable option in the clinical course of keratoconus. Furthermore, the outcome of PK for keratoconus seems to be independent of the patient's preoperative corneal curvature. In contrast, unfavourable BCVA preoperatively may be a negative predictor for the visual outcome.