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Phototherapeutic keratectomy (PTK) using bitoric ablation and collagen cross-linking (CXL) in the treatment of keratoconus

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Session Details

Session Title: Cross-Linking II

Session Date/Time: Tuesday 16/09/2014 | 16:30-18:00

Paper Time: 17:26

Venue: Boulevard A

First Author: : G.Rocha CANADA

Co Author(s): :    V. Penner   K. Lewis           

Abstract Details


To demonstrate the clinical outcomes of bitoric (cross-cylinder) phototherapeutic keratectomy (PTK) when combined with collagen crosslinking (CXL) in the treatment of keratoconus.


Retrospective chart review of eyes having undergone PTK/CXL at a single private practice centre.


50 keratoconic eyes of 36 patients were included. RT-Vue Optical Coherence Tomography (OCT) was used to plan an epithelial ablation, which was then performed until breakthrough occurred. Amoils brush cleared a 6-7 mm zone. A bitoric stromal ablation not exceeding 40 microns was then carried out, specifically targeting the astigmatic error. CXL was then carried out respecting the standard of 400 microns of corneal thickness.


Of the 50 eyes, 25 eyes had reached the 6 month follow-up. The average age was 32 ±12.5 years. Uncorrected visual acuity improved from 0.58 to 0.10 logMAR (p < 0.001), with best corrected visual acuity improving from 0.19 to 0.09 logMAR (p=0.04). On manifest refraction, the average spherical component decreased from -4.09 to -0.70D (3.39 ±2.37 p<0.001). Cylinder decreased from 3.25 to 1.45D (1.80 ±1.48 D p<0.001). Total HO increased from 1.49 to 1.55 (0.06±0.77 p=0.7). Decreases were seen in Spherical Aberration: -0.279 to -0.102 (0.177 ±0.428 p=0.07); 2nd Astigmatism: 0.307 to 0.287 (0.020 ±0.220 p=0.7); Coma: 1.117 to 1.115 (0.002 ±0.741 p= 0.99) and Trefoil: 0.663 to 0.638 (0.025 ±0.281 p=0.7). Corneal indices as calculated by the Oculus Pentacam all improved except IVA. Keratoconous Index improved 1.19 to 1.17 (0.02 ±0.04 p=0.02); Central Keratoconus Index improved 1.07 to 1.04 (0.03 ±0.04 p=0.004); Decentration was unchanged at 0.065; Topographic Keratoconus Classification improved 1.8 to 1.5 (0.3 ±0.6 p=0.01). Simulated central keratometry flattened by 2.60±2.54D (p<0.001) in the flatter meridian and flattened by 2.84±3.00D (p<0.001) in the steeper meridian. The central anterior cornea flattened by 4.60±5.24D (p<0.001).


PTK employing a bitoric ablation followed by CXL in the treatment of keratoconus provides dramatic improvements in uncorrected and best corrected visual acuities. These improvements stem from the significant reduction in both the spherical and cylindrical components of the manifest refractive error. Higher order aberrations are unchanged at 6 months followup. As would be expected in PTK, the central cornea flattened significantly and was reflected on Scheimpflug imaging. The use of bitoric PTK/CXL appears to be a promising procedure in managing keratoconus.

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