[Excimer laser-assisted keratoplasty is successful in the management of complex cases of intracorneal ring segments in keratoconus].

Abstract

Introduction: Analysis of visual acuity, keratometry and aberrometry (coma) after intrastromal corneal ring segment (ICRS) implantation in keratoconus (KC) and the evolution of visual acuity after subsequent excimer laser-assisted penetrating keratoplasty (PKP).

Patients and methods: Retrospective analysis of a case series of 7 patients from the Homburg Keratoconus Center (HKC), who received excimer laser PKP for unsatisfactory visual acuity 3.2 ± 3.0 years after ICRS implantation. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA) in logMAR, flat (K1), steep (K2) and mean keratometry, (Kmean), higher order aberrations (HOA, coma) and regularity of astigmatism were analyzed via tomography. Data of the PKP group (PG) were compared to a control group (CG) of 7 age-adapted satisfied patients after ICRS implantation without the need of PKP. Data analysis was performed before and 7.4 ± 4.5 months after PKP.

Results: Prior to PKP, data analysis showed a significantly lower UCVA of 0.94 ± 0.54 and BCVA of 0.49 ± 0.07 in the PG compared to the CG (UCVA 0.40 ± 0.35; CDVA 0.06 ± 0.05, p < 0.01). The K1 was significantly higher in the PG prior to PKP compared to the CG (47.1 ± 3.1 vs. 43.0 ± 2.7 D, p = 0.02) but K2 (p = 0.86) and Kmean (p = 0.12) were not. Regularity of peripheral (p = 0.54) and central (p = 0.69) astigmatism as well as coma (p = 0.39) did not show significant differences between the PG and KG prior to PKP. Excimer laser-assisted PKP was possible without any obstacles in all 7 eyes. In addition, BCVA increased significantly from 0.49 ± 0.07 to 0.33 ± 0.1 (p < 0.001) 6 months after PKP. The K1 decreased significantly after PKP (p = 0.002).

Conclusion: After unsuccessful ICRS implantation, patients seem to present with lower visual acuity and higher K1 despite similar values for K2, Kmean and coma. These patients may profit from an excimer laser assisted PKP, which can be performed without any obstacles despite the ICRS in place.