Abstract
AIM: To present the results of same-day topography-guided photorefractive keratectomy (TG-PRK) and corneal collagen crosslinking (CXL) after previous intrastromal corneal ring segment (ISCR) implantation for keratoconus.
METHODS: An experimental clinical study on twenty one eyes of 19 patients aged 27.1 +/- 6.6y (range 19-43y), with low to moderate keratoconus who were selected to undergo customized TG-PRK immediately followed by same -day CXL, 9mo after ISCR implantation in a university ophthalmology clinic. Refraction, uncorrected distance visual acuities (UDVA) and corrected distance visual acuities (CDVA), keratometry (K) values, central corneal thickness (CCT) and coma were assessed 3mo after TG-PRK and CXL.
RESULTS: After TG -PRK/CXL: the mean UDVA (logMAR) improved significantly from 0.66 +/- 0.41 to 0.20 +/- 0.25 (P<0.05); K-flat value decreased from: 48.44 +/- 3.66 D to 43.71 +/- 1.95 D; K-steep value decreased from 45.61 +/- 2.40 D to 41.56 +/- 2.05 D; K-average also decreased from 47.00 +/- 2.66 D to 42.42 +/- 2.07 D (P<0.05 for all). The mean sphere and cylinder decreased significantly post - surgery from, -3.10 +/- 2.99 D to -0.11 +/- 0.93 D and from -3.68 +/- 1.53 to -1.11 +/- 0.75 D respectively, while the CDVA, CCT and coma showed no significant changes. Compared to post-ISCR, significant reductions (P<0.05 or all) in all K values, sphere and cylinder were observed after TG-PRK/CXL.
CONCLUSION: Same -day combined topography guided PRK and corneal crosslinking following placement of ISCR is a safe and potentially effective option in treating low -moderate keratoconus. It significantly improves all visual acuity, reduced keratometry, sphere and astigmatism, but causes no change in central corneal thickness and coma.