Abstract
Purpose: To report long-term clinical results of transepithelial cross-linking with iontophoresis (I-CXL) for progressive keratoconus (KC). Methods: Nineteen eyes of 19 patients treated with I-CXL for progressive keratoconus were included in this prospective clinical study. Preoperatively and in all available follow ups (6, 12, 24, 36, 48, 60, 72 and 84 months), the following parameters were measured. Corrected distance visual acuity (CDVA), spherical equivalent and cylinder refraction, corneal topography and aberrometry (Costruzione Strumenti Oftalmici (C.S.O.), Florence, Italy), Scheimpflug tomography (OCULUS Optikgeräte GmbH; Wetzlar, Germany). Definition of progression after I-CXL was 2/3 of the following criteria: increase of “A” value, increase of “B” value, decrease of minimal thickness evaluated with the ABCD progression display above 95% confidence interval for post-CXL population when compared to the scan 12 months post-op. Results: The mean follow-up time of included patients was 63 months (range 12 to 84 months, 5 patients reached 84 months). The general linear model showed no significant change over time in CDVA, Maximum Keratometry, Thinnest point, and A, B, C values of the Belin Progression Display (p > 0.05). Conversely, comatic and high order aberrations decreased significantly over time (both p =< 0.001). Five cases (26.31%) showed significant progression after a mean of 55 months (range 36–72) of follow up. Conclusion: Our study shows the ability of I-CXL to slow down KC progression in the majority of included patients, improving high order and comatic aberrations. A 26% progression rate was reported.
Highlights
IntroductionThe first technique was introduced by Dresden University, and it included epithelial removal to allow riboflavin to penetrate corneal stroma (Standard-CXL; standard epithelium-off CXL (S-CXL)) [7]
Corrected distance visual acuity (CDVA) data are expressed in Snellen, while refractive outcomes are shown using the methods of Harris and Kaye after transforming the data into Long’s matrix formalism [23,24,25]
Iontophoresis cross linking (I-CXL) is considered a good alternative to standard epithelium-off CXL (S-CXL) for the treatment of progressive KC, even if it is known to induce a limited flattening when compared to S-CXL [16,17,18]
Summary
The first technique was introduced by Dresden University, and it included epithelial removal to allow riboflavin to penetrate corneal stroma (Standard-CXL; S-CXL) [7]. To avoid epithelial removal and its complications, many alternative transepithelial techniques and riboflavin solutions have been proposed [9,10,11,12]. Most of them did not provide encouraging results when compared to S-CXL [13]. Another solution that was introduced is iontophoresis cross-linking (I-CXL), a procedure in which the drug is applied with an electrode of the same drug charge. A recent long-term study presented 5 years results; the published technique differs from the one suggested by the manufacturer (the authors used two continuous cycles of 5 mA/5 min) [20]
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