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P. S. Hersh, K. L. Fry; Corneal Thickness Changes During Corneal Collagen Crosslinking. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5490.
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To investigate corneal thickness changes during corneal collagen crosslinking (CXL) for keratoconus and ectasia.
Forty-seven patients (50 eyes) underwent CXL for keratoconus (KC) or ectasia (32 and 18 eyes respectively). CXL was performed using the UVX system (Peschke Meditrade GmbH) using the method of Seiler and colleagues. Ultrasound pachymetry (Sonogage) measurements were taken before treatment, after epithelial debridement, after administration of riboflavin 0.1% plus dextran every 2 minutes for 30 minutes, after use of hypotonic riboflavin 0.1% if required, and at the conclusion of 30 minutes of UV exposure (365nm at irradiance of 3mW/cm2) with concomitant riboflavin 0.1% plus dextran administration every 2 minutes.
Mean initial corneal thickness was 451.3µm (ranging 330 to 575). Mean epithelial thickness was 52.7µm (ranging from 13 to 102). No differences in epithelial thicknesses were seen between KC and ectasia eyes. Following debridement, mean thickness was 383.2µm (ranging 269 to 505). After riboflavin 0.1% plus dextran for 30 minutes, mean thickness was 355.8µm (ranging 228 to 510). The cornea thinned in 37 eyes (74%), swelled in 12 eyes (24%) and was unchanged in 1 eye (2%) during initial 30 minute administration of the riboflavin. Thirty-nine of the 50 eyes (78%) required the use of hypotonic riboflavin to achieve the minimum corneal thickness of 400µm for UV irradiance. For all eyes, mean thickness was 421.0µm (ranging 401 to 510) before UV irradiance and after hypotonic riboflavin 0.1% use if was necessary). Mean corneal thinning with 30 minute UV exposure was 129.5µm (SD 41.0); cornea thinning was comparable in KC and ectasia eyes (133.2 µm (SD 41.8); 123.1µm (SD 40.2) respectively). There was no difference between the hypotonic riboflavin and no hypotonic needed groups (132.0µm (SD 36.8); 120.7µm (SD 55.2) respectively). At the conclusion of UVX treatment, mean thickness was 291.4µm (ranging 209 to 391).
The cornea undergoes considerable change in corneal thickness throughout the CXL procedure. The optimal method of using hypotonic riboflavin or other methods to increase and maintain corneal thickness throughout CXL remains to be elucidated.
Clinical Trial: :
www.clinicaltrials.gov NCT 00647699 & NCT 00674661
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