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Gerald Schmidinger; Pachymetry Changes During Corneal Cross-linking With Riboflavin And Ultraviolet -a Radiation: Effect Of Hypotonic Riboflavin Solution. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5213.
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To evaluate pachymetry changes during cross linking with open lids and closed lids and the effect of hypotonic riboflavin in thin corneas.
In a prospective, clinical trial 20 eyes of 20 patients with progressive keratoconus underwent corneal cross-linking (CXL). All CXL treatments included corneal abrasion under topical anaesthesia with subsequent installation of riboflavin 0,1 % solution for 30 minutes. In group one, a lid speculum was used during the procedure. In group two, the lids were closed during the loading phase with Riboflavin, and a lid speculum was used during the irradiation phase only. In patients with corneas thinner than 400µm after the loading phase, hypotonic Riboflavin was used to swell the corneas for 10 minutes. Pachymetry was measured at the thinnest point with an ultrasound pachymetry device (SP-2000, Tomey, Inc.) preaoperatively, after epithelium removal, and then every 10 minutes.
The mean preoperative pachymetry in group 1 was 466±23 µm and 477±28 µm in group 2. After removal of the epithelium the pachymetry was 415±20 µm and 430±35 µm in group one and two, respectively. In group two, the pachymetry remained stable throughout the loading phase, resulting in a pachymetry of 428 ± 50 µm after 30 minutes. In group one the pachymetry decreased to 355 ± 23 µm after 30 minutes. Swelling with hypotonic Riboflavin solution for ten minutes resulted in a mean increase of the pachymetry of 54 µm. During the irradiation phase, a reduction of the pachymetry was found in both groups. At the 40 minutes measurement the swelling effect of the hypotonic Riboflavin was already lost again in group one.
Isotonic riboflavin in a solution with 20% dextran leads to corneal dehydration during the loading phase. This effect can be reduced by not using a lid speculum during the loading phase. The use of a hypotonic Rioflavin solution results in an increase in corneal pachymetry, but this effect is lost within ten minutes.
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