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S. A. Greenstein, K. L. Fry, P. S. Hersh; Corneal Haze After Collagen Crosslinking: Natural History and Clinical Effects. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4973.
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To investigate the natural course and clinical correlation of corneal haze, as measured by Scheimpflug imaging, after collagen crosslinking, for patients with keratoconus and post-LASIK ectasia.
Corneal collagen crosslinking (CXL) was performed on 59 eyes, 40 with keratoconus and 19 with ectasia, in a prospective, randomized, controlled clinical trial. The treatment group received UVA/riboflavin therapy, and the control group received riboflavin therapy alone. Objective corneal densitometry (haze) was measured over a central 4 mm segment of the cornea using Scheimpflug images at baseline, 1,3,6, and 12 months, and was correlated with clinical outcomes of visual acuity (UCVA and BCVA), manifest refraction, manual and Pentacam topography (Kmax, Ksteep, Kflat, and Kaverage), and pachymetry. The Pentacam quantifies the haze of the cornea on a scale from 0 to 100.
Preoperative haze was 15.1 ± 2.51. Haze peaked at 1 month (23.6 ± 4.97, p<0.001). No significant change was seen at the 3 month examination (22.3 ±5.16, p<0.001). Haze significantly decreased between 3 and 6 months (19.5 ± 4.91, p<0.001), and continued to resolve through 12 months (17.1 ± 4.41, p<0.001). At 12 months, however, haze had not completely returned to baseline. Analysis of the keratoconus and ectasia subgroups followed a similar course. However, the ectasia group did return to baseline at 12 months (15.8 ± 2.30, p=0.27). No significant changes in haze were observed in the control group. Increased haze did not correlate with postoperative clinical outcomes (visual acuity, refraction, corneal curvature changes and corneal thickness).
Haze occurs after CXL, and can be objectively quantified using Scheimpflug imagery. Eyes show an increase in postoperative haze, peaking at 1 month, plateauing at 3 months, and significantly resolving between 3 and 12 months postoperatively. The quantity of haze does not appear to correlate positively or negatively with postoperative clinical outcomes.
Clinical Trial: :
www.clinicaltrials.gov NCT00647699 & NCT00674661
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