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A comparison of visual outcomes after CXL combined with epithelial PRK (CXL-ePRK) and Topography Guided PRK (CXL-TGPRK)

Poster Details

First Author: M.Mimouni CANADA

Co Author(s):    I. Kaiserman   N. Sorkin   W. Hatch   R. Stein   N. Singal        

Abstract Details


Corneal crosslinking (CXL) is the standard treatment for delaying or halting the progression of keratoconus. The purpose of the current study is to compare visual outcomes after CXL combined with epithelial photorefractive keratecotmy (PRK) (CXL-ePRK) (Tel-Aviv Protocol) versus topography guided PRK (CXL-TGPRK).


A post-hoc analysis of data from two centers, the Kensington Eye Institute, Toronto, Canada and Care Vision Laser Centers, Tel-Aviv, Israel.


The following preoperative data was recorded: age, gender, central corneal thickness, k1, K2, maximum keratometry, uncorrected distance visual acuity (UDVA), best spectacle corrected visual acuity (BSCVA), sphere, cylinder and coma. The following postoperative data was collected: central corneal thickness, mean keratometry, maximum keratometry, minimum keratometry, UDVA, BSCVA, sphere, cylinder and higher order aberrations. The primary outcome measures were change in UDVA and CDVA following each of the procedures. Secondary outcome measures were change in: keratometry values, pachymetry, refractive error and higher order aberrations.


Overall 93 CXL-TGPRK and 50 CXL-ePRK were included. There were significant differences between groups in terms of baseline age, UDVA, refractive error, BSCVA and CCT (p<0.05 for all). Both groups significantly improved in terms of UDVA, refractive error and BSCVA with a decrease in CCT (p<0.05 for all). When comparing adjusted (for baseline) postoperative outcomes between groups, CXL-ePRK was superior (mean difference) for postoperative UDVA (0.44±0.11 logMAR, p<0.001), spherical equivalent (1.73±0.87D, p=0.05), sphere (2.51±0.92D, p=0.007), cylinder (1.57±0.63D, p=0.01) and efficacy index (0.47±0.14, p=0.001). There were no significant differences in postoperative CCT (p=0.87).


Both CXL-ePRK and CXL-TGPRK provide improved uncorrected and corrected vision for keratoconus patients while stabilizing keratometry indices at the expense of a decreased CCT. It seems as though CXL-ePRK may offer superior uncorrected visual acuity by reducing the amount of myopia and cylinder at a greater magnitude than CXL-TGPRK.

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