Corneal thickness changes during corneal collagen cross-linking with UV-A irradiation and hypo-osmolar riboflavin in thin corneas

Abstract

Purpose: To evaluate the thinnest corneal thickness changes during and after corneal collagen cross-linking treatment with ultraviolet-A irradiation, using hypo-osmolar riboflavin solution in thin corneas. Methods: Eighteen eyes of 18 patients were included in this study. After epithelium removal, iso-osmolar 0.1% riboflavin solution was instilled to the cornea every 3 minutes for 30 minutes. Hypo-osmolar 0.1% riboflavin solution was then applied every 20 seconds for 5 minutes or until the thinnest corneal thickness reached 400 µm. Ultraviolet-A irradiation was performed for 30 minutes. During irradiation, iso-osmolar 0.1% riboflavin drops were applied every 5 minutes. Ultrasound pachymetry was performed at approximately the thinnest point of the cornea preoperatively, after epithelial removal, after iso-osmolar riboflavin instillation, after hypo-osmolar riboflavin instillation, after ultraviolet-A irradiation, and at 1, 6 and 12 months after treatment. Results: Mean preoperative thinnest corneal thickness was 380 ± 11 µm. After epithelial removal it decreased to 341 ± 11 µm, and after 30 minutes of iso-osmolar 0.1% riboflavin drops, to 330 ± 7.6 µm. After hypo-osmolar 0.1% riboflavin drops, mean thinnest corneal thickness increased to 418 ± 11 µm. After UVA irradiation, it was 384 ± 10 µm. At 1, 6 and 12 months after treatment, it was 372 ± 10 µm, 381 ± 12.7, and 379 ± 15 µm, respectively. No intraoperative, early postoperative, or late postoperative complications were noted. Conclusions: Hypo-osmolar 0.1% riboflavin solution seems to be effective for swelling thin corneas. The swelling effect is transient and short acting. Corneal thickness should be monitored throughout the procedure. Larger sample sizes and longer follow-up are required in order to make meaningful conclusions regarding safety.

Isotonic Riboflavin and HPMC With Accelerated Cross-Linking Protocol

“…No significant change was noticed in the pachymetry readings after UV-A radiation compared with the preoperative pachymetry reading. 8,[10][11][12][13] A modification to the technique of CXL was introduced, so that corneas thinner than 400 mm after abrasion of the epithelium become eligible for treatment. 7 HPMC is nonirritant to ocular tissue and can be used for prolonged periods without any damage to the eye.…”

“…7 HPMC is nonirritant to ocular tissue and can be used for prolonged periods without any damage to the eye. 12 Keeping these facts in perspective, we modified our study and used isotonic riboflavin with HPMC during the saturation phase and the accelerated protocol thereby reducing the duration of UV-A irradiation to 10 minutes instead of 30 minutes. Also, compared with the breakup time of the dextran-riboflavin film, which is 22 minutes, HPMC-riboflavin is approximately 32 minutes.…”

“…A minimum of 400 mm of corneal thickness has been recommended to guarantee sufficient absorption of 365-nm UV-A light in the corneal stroma when using the standard protocol. [9][10][11][12][13] Although dextran adds to the viscosity of the solution, it also causes considerable decrease in corneal thickness during the procedure. In addition, a significant reduction in corneal pachymetry can be observed during saturation of the stroma with riboflavin.…”

Changes in corneal sensitivity following cross-linking for progressive early-stage keratoconus

“…Our group (25) recently described transient corneal thinning after corneal CXL with UVA irradiation and a hypo-osmolar riboflavin solution in thin corneas (<400 µm) for progressive keratoconus. In our analysis of changes in corneal thickness over time, pachymetric values decreased until 1 month after surgery and appeared to increase thereafter.…”

Corneal Collagen Crosslinking with Riboflavin and Ultraviolet - A Irradiation in the Management of Progressive Ectatic Corneal Disorders. Review Article

“…According to "equal-dose" principle 10mW/cm and reducing the exposure time to 9 minutes produces a similar increase in corneal stiffness to that gained using the standard procedure 66 . Several recent in vivo studies using different protocols showed the procedure to be safe and effective in stopping ectasia progression [69][70][71][72] . Kanellopoulos AJ 57 reported efficacy of CXL in early keratoconus with riboflavin delivered in a femtosecond laser-created pocket, thus avoiding the need to remove the epithelium or use other drugs.…”