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Data from 1 year of follow-up for 146 eyes with corneal ectatic disease treated with simultaneous phototherapeutic keratotomy, topography-guided PRK, and collagen crosslinking show significant improvements in refraction, keratometry, visual function, and quality of vision.
By Cheryl Guttman Krader; Reviewed by Avi Wallerstein, MD
Montreal-Phototherapeutic keratotomy (PTK) followed by topography-guided PRK (TG-PRK) and immediate collagen crosslinking (CXL) is safe and effective treatment for progressive corneal ectasia, according to 1-year follow-up data presented by Canadian.
Avi Wallerstein, MD, and Mark Cohen, MD, co-founders of LASIK MD in Canada, together with 14 LASIK MD surgeons in ten clinic locations have performed the multimodal technique to treat 726 eyes with keratoconus or ectasia following laser vision correction surgery. Tenley N. Bower, MD, ophthalmology resident, McGill University, Montreal, reported outcomes from a retrospective analysis that had 1 year of follow-up.
The updated study results as of March 2013, included 146 eyes: 111 eyes with keratoconus and 35 with postoperative ectasia; 42 of the 104 patients in the series had bilateral treatment.
At 1 year, there were significant improvements in uncorrected visual acuity (UCVA) and best corrected visual acuity (BCVA) associated with significant reductions in sphere, cylinder, and maximum keratometry (Kmax) values. Additionally, patients noted overall improvement in quality of vision.
“There are various treatments for corneal ectatic conditions,” Dr. Wallerstein said. “Some patients undergo CXL alone or with corneal ring segments, others have TG-PRK with CXL, or as in this series, patients can have simultaneous PTK with TG-PRK and CXL. The transepithelial PTK takes advantage of epithelial remodeling seen with ectatic conditions to differentially shave tissue off the cone, where epithelium is thinnest. TG- PRK helps to normalize irregular astigmatism by further ablating and flattening the cone, steepening the flat area adjacent to the cone, and correcting the cylinder. Performing CXL immediately after locks in the results.
“Our study showed this approach resulted in objective improvements, but we also found the patients benefited with better uncorrected and best corrected quality of vision,” he said. “We believe that represents an important change because of its significant impact on patient quality of life.”
In the multistep treatment, the PTK removes between 50 and 70 μm of tissue including epithelium and some stroma over the cone. Then, the TG-PRK is performed with a proprietary platform in which the ablation profile is computed by proprietary software (topography-guided customized ablation treatment, T-CAT; Alcon) of a specific excimer laser platform (Wavelight, Alcon) based on data acquired with a high-resolution Placido disc topographer (Topolyzer, Alcon). Dr. Mark Cohen created the Montreal Protocol whereby a nomogram modifies the sphere, cylinder power and axis, as well zone size to increase accuracy in outcomes. After the TG- PRK, mitomycin-C 0.02% is applied to the cornea with an 8-mm sponge for 2 minutes. Then CXL is performed with UVA of 18 mW/cm2 for 5 minutes.
Mean distance UCVA improved significantly by an average of ~6 Snellen lines from logMAR 1.13 preoperatively to 0.55 at 12 months when 27% of eyes achieved 20/25 or better and 39% were 20/30 or better. Mean BCVA improved by an average of 1 Snellen line from logMAR 0.27 preoperatively to 0.18 at 12 months; more than 40% of eyes gaining 1 or more lines of BCVA, although 3 eyes (3%) lost 3 lines.
Manifest refraction spherical equivalent was reduced from -3.2 D preoperatively to -1.5 D at 1 year, mean sphere was reduced from -1.2 to -0.3 D, and mean cylinder decreased from -4.0 to -2.5 D. All of the refractive changes were highly statistically significant (P<0.001) as was the reduction in mean Kmax, which decreased from 48.2 D preoperatively to 45.1 D at 12 months.
Quality of vision was investigated using a modified version of the Quality of Vision questionnaire published by McAlinden et al [Invest Ophthalmol Vis Sci 2010;51:5537-5545]. The questionnaire asked patients to rate their vision using a scale of 0 (worst) to 10 (best) and was completed preoperatively and at 6 months.
The uncorrected quality of vision score increased from a mean of 4.2 to 5.8 at 6 months when 79% of patients reported an improvement, 5% said they had no change, and 16% reported worsening. In ratings of corrected quality of vision, the mean score improved from 6 to 7.2. Again, 56 % of patients rated their quality of corrected vision as better, 18% rated it as worsened, and 25 % said it was unchanged.
“We expect that the quality of vision scores at 1 year should be significantly better than at 6 months because of improvement in surface irregularity as well as diminution of haze with time,” Dr. Wallerstein said.
Avi Wallerstein, MD
None of the authors has any relevant financial interests to disclose. This article is adapted from the authors’ presentation during Refractive Surgery 2012 at the annual meeting of the American Academy of Ophthalmology.