Korean J Ophthalmol.  2016 Oct;30(5):326-334. 10.3341/kjo.2016.30.5.326.

The Long-term Clinical Outcome after Corneal Collagen Cross-linking in Korean Patients with Progressive Keratoconus

  • 1Department of Ophthalmology, Kyung Hee University Medical Center, Kyung Hee University School of Medicine, Seoul, Korea. khjinmd@khmc.or.kr


To evaluate the long-term clinical effectiveness and safety of corneal collagen cross-linking (CXL) in progressive keratoconus compared with untreated contralateral eyes.
In this retrospective study, nine eyes of nine patients with progressive keratoconus who received CXL (treatment group) and nine untreated contralateral eyes with keratoconus (control group) were included. All patients were followed for at least 5 years and assessed with best-corrected visual acuity, maximum keratometry, mean keratometry, corneal astigmatism, and corneal thickness. Clinical data were collected preoperatively and at 1, 3, 6, 12, 24, 36, 48, and 60 months, postoperatively.
Mean best-corrected visual acuity improved significantly from 0.58 ± 0.37 logarithm of minimum angle of resolution preoperatively to 0.39 ± 0.29 logarithm of minimum angle of resolution at 5 years after corneal CXL (p = 0.012). There was significant flattening of the maximum keratometry and mean keratometry from preoperative values of 63.39 ± 10.89 and 50.87 ± 6.27 diopter (D) to postoperative values of 60.89 ± 11.29 and 49.54 ± 7.23 D, respectively (p = 0.038, 0.021). Corneal astigmatism decreased significantly from 7.20 ± 1.83 D preoperatively to 5.41 ± 1.79 D postoperatively (p = 0.021). The thinnest corneal thickness decreased from 434.00 ± 54.13 to 365.78 ± 71.58 µm during 1 month after treatment, then increased to 402.67 ± 52.55 µm at 5 years, which showed a statistically significant decrease compared to the baseline (p = 0.020). In the untreated contralateral eyes, mean keratometry increased significantly at 2 years compared with the baseline (p = 0.043).
CXL seems to be an effective and safe treatment for halting the progression of keratoconus over a long-term follow-up period of up to 5 years in progressive keratoconus.


Cross-linking; Keratoconus; Riboflavin; Ultraviolet rays

MeSH Terms

Follow-Up Studies
Retrospective Studies
Treatment Outcome
Ultraviolet Rays
Visual Acuity


  • Fig. 1 Comparison of the mean change relative to baseline in best-corrected visual acuity (BCVA) (A), maximum keratometry (Kmax) (B), mean keratometry (Kmean) (C), corneal astigmatism (D), and thinnest corneal thickness (E) at each time point in the treatment and control groups. At each time point, the bar represents the mean change from baseline, and the p-value is calculated using the independent sample t-tests between the control and the treatment groups.

  • Fig. 2 Bar graphs demonstrating best-corrected visual acuity changes (lines) 5 years after corneal cross-linking in keratoconic patients (A) and in the control group (B).


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