Accelerated, Pulsed Collagen Cross-Linking versus the Dresden Protocol in Keratoconus: A Case Series

Abstract

Purpose: The aim of our study was to compare the depth of the demarcation line developing in the cornea after the standard Dresden protocol versus the accelerated, pulsed, epithelium-off corneal collagen cross-linking (CXL). Methods: This was a nonrandomized, retrospective case series. Patients with progressive keratoconus were treated with either the standard Dresden protocol (Group 1) or accelerated, epithelium-off CXL using the Avedro (Waltham, MA, USA) device (Group 2). The accelerated CXL protocol involved 18 min of pulsed ultraviolet-A (20 mW/cm², 7.2 J/cm², pulsed pro-file: 1 s on, 2 s off). The depth of the demarcation line was measured about 3 months postoperatively. Results: Fifty-nine eyes of 35 subjects were included in the analysis. Group 1 consisted of 19 eyes, and Group 2 of 40 eyes. The mean age of the participants was 22.21 years in Group 1 and 26.55 years in Group 2 (p = 0.184). The mean preoperative K value was 44.89 D in Group 1 and 45.20 D in Group 2 (p = 0.768). The depth of the demarcation line was 322.50 μm in Group 1 and 319.95 μm in Group 2 (p = 0.937). Conclusions: The demarcation line depth was not statistically significantly different between the two protocols. The significance of the demarcation line depth has not been fully clarified in the literature. Our results support the contention that these two techniques may have similar structural outcomes and ef­ficacies in the treatment of keratoconus.

Clinical, Anatomical, and Densitometric Changes following Dresden vs. Accelerated Corneal Cross-Linking in Progressive Keratoconus

“…They found that during the first 10 – 15 seconds of continuous 3 mW/cm² illumination, photooxidation occurs with photochemically generated ROS, producing covalent bonds between collagen und proteoglycan molecules under aerobic conditions in a type II photochemical mechanism 23 , 24 . After 10 – 15 seconds, oxygen becomes rapidly depleted and the reaction moves to a type I photochemical mechanism under anaerobic conditions, leading to the formation of fewer covalent bonds 23 , 25 . Interestingly, when using 30 mW/cm² irradiance, oxygen was already depleted after 5 seconds.…”

Management of Keratoconus in Down Syndrome and Other Intellectual Disability

“…All treated patients had accelerated protocol epithelium-off CXL comprising 8-mm alcohol-assisted epithelial debridement and isotonic riboflavin 0.1% saturation (Vibex Rapid; Medio-Haus-Medizinprodukte GmbH, Kiel, Germany) for 10 minutes and 4 minutes of ultraviolet A irradiation with a total energy of 30 J/m 2 shown to be comparable with the Dresden protocol for nonadvanced KC. 22,23 After the procedure, all patients were treated with topical steroid (prednisolone acetate 1% QID; Allergan plc) for 2 weeks and topical antibiotic prophylaxis (chloramphenicol 0.5% QID) until reepithelialization. Patients were reviewed at 1 week for removal of bandage contact lens, then 1 month and 6 months.…”

A comprehensive review on corneal crosslinking

“…Pulsating UVA radiation can lead to higher oxygen concentrations and therefore promoting an increase in the Type II photochemical mechanism. [ 17 ] When compared to the conventional protocol, pulsed light treatment seems to be able to possibly penetrate deeper in the corneal stroma, with a similar efficacy and safety profile. [ 18 ]…”