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Comparison of the Conventional Dresden Protocol and Accelerated Protocol With Higher Ultraviolet Intensity in Corneal Collagen Cross-Linking for Keratoconus

Choi, Moonjung MD; Kim, Jiwon MD; Kim, Eung Kweon MD, PhD; Seo, Kyoung Yul MD, PhD; Kim, Tae-im MD, PhD

doi: 10.1097/ICO.0000000000001165
Clinical Science

Purpose: To compare the accelerated corneal cross-linking (CXL) protocol and the conventional Dresden protocol in patients with keratoconus in terms of visual acuity, keratometric values, and topographic parameters.

Methods: Twenty-eight eyes of 25 patients with primary keratoconus were divided into 2 groups; 15 eyes in group 1 received CXL under the standard Dresden protocol (3 mW/cm2 for 30 min, dose 5.4 J/cm2) and 13 eyes in group 2 were treated with the accelerated protocol (30 mW/cm2 for 3 min 40 s, dose 6.6 J/cm2). Visual acuity, refractive error, keratometry values obtained by both Pentacam and Auto Kerato-Refractometer, corneal thickness, and topometric indexes were compared 6 months postoperatively.

Results: The visual acuity improved significantly from 0.17 ± 0.16 to 0.08 ± 0.09 logarithm of the minimum angle of resolution in group 1 (P = 0.009). The cylindrical refractive error improved in both groups (P = 0.05 in group 1 and P = 0.011 in group 2), and the spherical equivalent increased in group 1 (P = 0.021). In group 1, the maximum keratometry value decreased by 0.55 ± 0.89 diopters (P = 0.03), and the mean keratometry value decreased by 0.44 ± 0.63 diopters (P = 0.017), whereas the changes in visual acuity, spherical and spherical equivalent refractive errors, and keratometric values in group 2 were not statistically significant. The corneal thickness at the apex decreased significantly in group 1 (P = 0.001), but the change was not significant in group 2.

Conclusions: Despite a higher UV dose (6.6 J/cm2), accelerated CXL with higher UV intensity and reduced irradiation time showed a smaller topographic flattening effect than did the conventional Dresden protocol in primary keratoconus with documented progression.

*Department of Ophthalmology, Institute of Vision Research, Yonsei University College of Medicine, Seoul, South Korea; and

Department of Ophthalmology, Cornea Dystrophy Research Institute, Yonsei University College of Medicine, Seoul, South Korea.

Reprints: Tae-im Kim, MD, PhD, Department of Ophthalmology, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-752, Korea (e-mail:

Supported by a grant from the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (HI14C2044).

The authors have no conflicts of interest to disclose.

M. Choi and J. Kim have contributed equally.

Received September 13, 2016

Received in revised form December 08, 2016

Accepted December 30, 2016

Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.