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Elan Aaron Rosenblat, Steven A Greenstein, Peter S Hersh; Corneal Thickness Changes and Results of Collagen Crosslinking using Riboflavin/Dextran or Hypotonic Riboflavin.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4223.
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This study was designed to compare the use of two riboflavin formulations, riboflavin 0.1% in 20% dextran solution and its hypotonic formulation without dextran with regard to intraoperative corneal thinning and clinical results.
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 400µm hypotonic riboflavin was administered until the cornea swelled beyond 400µm. 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 randomized study arms: 35 patients received riboflavin/dextran and 28 patients received hypotonic riboflavin every 2 minutes for the duration of UV exposure. Corneal thickness measurements were then analyzed between both arms of the study. Pachymetry was measured by ultrasound before the corneal epithelium was removed, after initial riboflavin loading prior to, and after UV light exposure. At least 5 pachymetry measurements were taken at each time point and the lowest used for analysis. Patients were then followed at 1, 3, 6 and 12 months postoperatively. If any patient missed an appointment they were removed from the study. Thirty nine patients with either keratoconus (29) or post lasik ectasia (10) who underwent corneal cross-linking remained in the study. 21 patients (15 keratoconus, 6 ectasia) received standard riboflavin dextran solution during UVA light administration and 18 patients (14 keratoconus, 4 ectasia) received a hypotonic riboflavin solution during UVA light administration.
Please see attached Figures.
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. These intraoperative changes were transient and there were no statistically significant difference in outcomes at 1, 3,6, or 12 month followup.
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