Sir,
Keratoconus is a progressive corneal ectasia with an estimated prevalence of 1 in 2000.1 Crosslinking (CXL) is used to stop the progression of keratoconus, whereas intrastromal corneal ring segment (ICRS) is used to improve functional vision.
Case report
We compared two sequences of combined ICRS implantation and CXL in progressive keratoconus. In this retrospective study, CXL was followed by ICRS implantation (group A) or ICRS implantation was followed by CXL (group B). Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, spherical equivalent (SE), manifest cylinder, mean keratometry (K), and maximum K were compared preoperatively and postoperatively. In all, 17 eyes of 10 patients with progressive keratoconus were included in this study, 11 eyes in group A and 6 in group B. The mean interval between treatments was 4.3 months in group A and 5 months in group B. The mean age was 27.6 in group A and 28.4 years in group B. The two groups were equivalent preoperatively. The mean UDVA and CDVA improved in both the groups (UDVA: 0.50±0.22 to 0.60±0.20 in group A and 0.28±0.19 to 0.62±0.22 in group B (P<0.05); CDVA: 0.64±0.15 to 0.70±0.14 and 0.70±0.14 to 0.88±0.17, respectively). The cylinder, mean K, and maximum K values decreased in both the groups (cylinder: −3.63±1.27 to −1.14±0.1 D (P<0.05) group A and −3.60±1.85 to −2.80D±2.19 D group B; mean K: 44.80 to 42.50 D (P<0.05) and 43.98 to 43.90 D; maximum K: 51.52±2.39 to 50.10±0.9 and 51.76±2.55 to 49.50±1, respectively). SE values decreased in group A (−3.4 to −0.50 D (P<0.05)), whereas it increased in group B (−1.10 to −1.70 D).
Comment
ICRS have been used to correct ectatic corneal diseases by reducing corneal steepening. CXL with riboflavin and ultraviolet A is a technique to increase corneal rigidity. Several studies showed that the association of CXL with ICRS led to better results.2, 3, 4, 5 In our study, there is no statistical difference between the two sequences: ICRS implantation followed by CXL or CXL followed by ICRS implantation. Overall, the two sequences show an improvement in UDVA, CDVA, cylinder, mean K, and maximum K.
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Saib, N., Bonnel, S., Fenolland, JR. et al. Intrastromal corneal rings and corneal collagen crosslinking for progressive keratoconus: comparison of two sequences. Eye 29, 294–295 (2015). https://doi.org/10.1038/eye.2014.285
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DOI: https://doi.org/10.1038/eye.2014.285
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