Evaluation of collagen crosslinking in keratoconus eyes with Kera intracorneal ring implantation

PURPOSE. To assess the outcome of collagen crosslinking (CXL) in keratoconus eyes after implantation of Kera intracorneal ring segments. PATIENTS AND METHODS. Twenty-one eyes of 13 patients with mild to moderate degree of keratoconus were included in this study. All eyes had uneventful surgery for Kera intracorneal ring segment implantation followed by collagen CXL treatment after at least 3 months of the implantation. Inclusion criteria were absence of corneal scarring and corneal thickness higher than 400 mm. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), spherical equivalent and cylinder refraction, and the mean keratometric (K) values were evaluated preoperatively and postoperatively. RESULTS. The mean age was 21.36 +/- 4.46 years (range 16-28). Mean time between implantation of Kera ring and CXL was 4.56 +/- 3.2 months. The mean baseline UCVA and BCVA were 0.05 +/- 0.02 and 0.18 +/- 0.1, respectively; after Kera ring, the mean UCVA and BCVA were 0.23 +/- 0.17 and 0.39 +/- 0.18 (p=0.000), respectively. Collagen CXL after Kera ring resulted in an additional change in UCVA and BCVA to become 0.23 +/- 0.17 (p=0.951) and 0.41 +/- 0.18 (p=0.08), respectively. Also, CXL results in an additional change in spherical equivalent,, cylindrical, and mean keratometric values. The decrease in spherical equivalent, cylindrical, and mean keratometric value was 2.8 D (p<0.05), 2.1 D (p<0.05), and 2.5 D (p<0.05), respectively, after Kera ring treatment. An additional decrease of 0.11 D (p>0.05), 0.01 D (p>0.05), and 0.09 D (p>0.05) was obtained after CXL in each respective parameter. CONCLUSIONS. Collagen CXL has an additive effect after Kera ring implantation and may be considered as an enhancement/stabilizing procedure.