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Elan Rosenblat, Alexander Sachs, Steven Greenstein, Peter Hersh; Corneal Thickness Changes during Collagen Crosslinking using Riboflavin/Dextran or Hypotonic Riboflavin. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5283.
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To compare the central corneal thickness between the use of riboflavin 0.1% in 20% dextran solution versus riboflavin 0.1% in water (hypotonic) during ultraviolet light exposure in the collagen crosslinking procedure for keratoconus and corneal ectasia.
63 eyes with keratoconus and corneal ectasia were analyzed in a prospective randomized control clinical trial. Both arms of the study received pretreatment with riboflavin 0.1% in 20% dextran solution; one drop was administered every 2 minutes for 30 minutes after the corneal epithelium was removed. If the corneal thickness was less than 400 microns hypotonic riboflavin was administered until the cornea swelled beyond 400 microns. Both study groups then received 30 minutes exposure to UV light (365 micron wavelength, irradiance 3mW/cm2). During UV exposure, eyes received continued riboflavin application, the formulation of which was assigned by 2 study arms: 35 patients received riboflavin/dextran and 28 patients received hypotonic riboflavin every 2 minutes for the duration of UV exposure. Pachymetry was measured by ultrasound before the corneal epithelium was removed, after initial riboflavin loading prior to UV light exposure, and after UV light exposure. At least 5 pachymetry measurements were taken at each time point and the lowest used for analysis. Corneal thickness measurements were then analyzed between both arms of the study.
The average initial pachymetry, pachymetry after 30 minutes riboflavin loading, and final pachymetry after UV light was 436.83, 429.89 and 301.80, respectively, in the riboflavin/dextran group, compared to 443.07, 432.29 and 341.06, respectively, in the hypotonic group. The difference in corneal thickness between the two groups was statistically significant when taken after UV administration. The p values between both study arms comparing the initial pachymetry, pachymetry after loading, and final pachymetry after UV light was 0.67, 0.77 and 0.0002, respectively.
The cornea thins substantially during the collagen crosslinking procedure. The use of hypotonic riboflavin rather than riboflavin/dextran during UV administration decreases the amount of corneal thinning during the procedure 24%, from thinning of 135 microns to 102 microns. This difference in corneal thinning may have both safety and efficacy implications for the CXL procedure.
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