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Peter S. Hersh, Steven Greenstein, Kristen Fry; Clinical Timecourse of Corneal Collagen Crosslinking. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4124.
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To define the timecourse of clinical results after corneal collagen crosslinking (CXL) for keratoconus and corneal ectasia.
Eighty-five eyes underwent CXL for keratoconus (n=56) or ectasia (n= 29) in a prospective, randomized controlled trial. Clinical outcomes, including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), maximum keratometry (Kmax), corneal topography indices, corneal and ocular wavefront analysis, questionnaire-assessed subjective visual function, CXL- associated corneal haze measured by Scheimpflug densitometry, and corneal thickness, were assessed and analyzed at baseline, 1 month, 3 months, 6 months, and 1 year.
Preoperative UCVA was 20/137 (logMAR 0.83), worsening to logMAR 0.91 at 1 month, and improved until one year, with UCVA 20/117 (logMAR 0.76). Preoperative BSCVA was 20/45 (logMAR 0.34), worsening to logMAR 0.38 at 1 month, and then improved until one year, with UCVA 20/34 (logMAR 0.24). At one year, improvements in night driving, reading, diplopia, glare, halo, and starbursts were significant. Preoperative Kmax was 58.5, worsening to 59.8 at 1 month, and then improved until one year Kmax was 56.9. 30.6% of eyes flattened by 2.0 D or more, and 3.5% steepened by 2.0D. Of seven corneal topography indices, there were significant improvements in index of surface variance, index of vertical asymmetry, keratoconus index, and minimum radius of curvature (p<0.001). There was a general worsening of topography indices at one month, followed thereafter by improvement. Analyzing corneal HOAs, total HOA, total coma, 3rd order coma, and vertical coma significantly decreased at one year after CXL, (p<0.001). For total ocular HOAs, total HOA, total coma, 3rd order coma, and trefoil decreased (p=0.01). The mean preoperative thinnest pachymetry was 440.7 µm. After CXL, the cornea thinned at 1 month (mean change –23.8 µm; P < .001) and from 1 to 3 months (mean change –7.2 µm, P = .002), followed by a recovery of the corneal thickness at 6 months (mean +20.5 µm; P<.001). At 1 year, pachymetry remained slightly decreased from baseline to 12 months (mean change –6.6 µm; P = .01). CXL-associated haze was 14.9±1.93 densitometry unit preoperatively, peaking at 1 month (mean=23.4±4.40,p<0.001); little change was seen at 3 months (22.4±4.79,p=0.06). Densitometry decreased between 3 and 6 (19.4±4.48, p<0.001), and 6 and 12 months, but did not completely return to baseline (mean = 17.0±3.82, p<.001).
Clinical outcomes of corneal collagen crosslinking follow a generally definable time course with worsening at one month, a return to baseline at 3 months, improvement at 6 & 12 months, and stabilization beyond 1 year. Most patients were stable or had topographic improvement over the year after CXL.
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