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Steven A. Greenstein, Kristen L. Fry, Peter S. Hersh; Corneal Collagen Crosslinking Outcomes With and Without Stromal Swelling with Hypotonic Riboflavin. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5195.
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It has been suggested that hypotonic riboflavin can be used to swell the corneal stroma to a safe level in order to perform corneal collagen crosslinking (CXL). In this investigation, we compare 1 year CXL clinical outcomes, using hypotonic riboflavin for corneal swelling vs. standard riboflavin dextran solution only.
103 eyes underwent CXL for keratoconus (n=68) or ectasia (n= 35) in a prospective, randomized controlled trial. Riboflavin (0.1% in 20% dextran T500 solution) was administered topically for 30 minutes. If the cornea was <400µm after this dosing, hypotonic riboflavin (0.1% in sterile water) was given, 1 drop every 10 seconds for 2 minute rounds, and ultrasonic pachymetry (U/S) was performed until the stroma had swollen to >400µm. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), maximum keratometry (Kmax), corneal haze, and thinnest pachymetry (Pthin) were compared between riboflavin groups.
In the riboflavin dextran only group (n=42), UCVA (logMAR change=-.07±0.19,p=.04), BCVA (logMAR change=-.09±0.17,p<.01), and Kmax (change=-1.2±1.9D,p<.01) significantly improved, and corneal haze returned to baseline at 1 year (p=.1). Preoperative Pthin was 468.2±48.2µm, and at 1 year was slightly thinner (458.2±47.5µm,p<.01). In the hypotonic group (n=61), preoperative U/S, U/S after 30 minutes of riboflavin dextran administration, and U/S after hypotonic riboflavin administration, was 423.9±53.7µm, 340.9±45.1µm, and 413.6±11.1µm, respectively. On average, 3.1±2.2 rounds of hypotonic drops were required to swell the cornea ≥400µm. In this group, UCVA (logMAR change=-.09±0.28,p=.01), BCVA (logMAR change=-.1±0.18,p<.01), and Kmax (change=-1.9±4.0D,p<.01) significantly improved, and corneal haze remained slightly above baseline at 1 year (p<.01). Preoperative Pthin was 423.1±51.1µm, and at 1 year returned to preoperative measurement (420.9±51.7µm,p=.4). There was no significant difference between the two riboflavin groups, when comparing the changes in any of these clinical outcomes at 1 year (PUCVA =.5, PBCVA =.6, PKmax = .2, PHaze =.1, PPthin = .1).
Administration of hypotonic riboflavin to swell the corneal stroma does not appear to affect 1 year clinical outcomes compared to standard riboflavin/dextran alone.
Clinical Trial: :
http://www.clinicaltrials.gov NCT00647699 & NCT00674661
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