ESCRS - FP02.06 - Individualized Corneal Cross-Linking (Cxl) In Ultrathin Corneas: The “Sub400” Protocol, 2 Year Follow-Up Data

Individualized Corneal Cross-Linking (Cxl) In Ultrathin Corneas: The “Sub400” Protocol, 2 Year Follow-Up Data

Published 2023 - 41st Congress of the ESCRS

Reference: FP02.06 | Type: Free paper | DOI: 10.82333/wtsd-8b84

Authors: Farhad Hafezi* 1 , Nanji Lu 2 , Sabine Kling 3 , Enes Aydemir 2 , Nikki L. Hafezi 2 , Shady Awwad 4 , Mark Hillen 2 , Emilio A. Torres-Netto 2

1Ophthalmology,ELZA Institute,Dietikon,Switzerland;Ocular Cell Biology Laboratory,University of Zurich,Zurich,Switzerland, 2Ophthalmology,ELZA Institute AG,Dietikon,Switzerland, 3Dept. of Information Technology and Electrical Engineering,ETH Zurich,Zurich,Switzerland, 4Medical Center,American University of Beirut,Beirut,Lebanon

Purpose

The original Dresden protocol for epi-off CXL relies on a minimal stromal thickness of 400 µm. However, advanced keratoconi show thicknesses of less than 400 µm and may still achieve useful vision with contact lenses. The first protocols to treat thin corneas were either unpredictable in thickness modification (swelling with hypo-osmolaric riboflavin) or showed a reduction of at least 30 % efficacy due to limited oxygen supply (contact lens-assisted CXL).

In 2021, we published the sub400 protocol, an epi-off CXL for ultrathin corneas that adapt the fluence based on the patient’s individual stromal thickness with a 1-year follow-up. Here, we investigated the success rate of the original sub400 study population with a 2-year follow-up.

Setting

ELZA Institute, Dietikon, Switzerland

Methods

Patients from the original sub400 study with progressive keratoconus and corneal stromal thicknesses below 400 µm were enrolled for the 2-year follow-up. After epithelium removal, UV-irradiation was individualized to the patient’s individual stromal thickness using a published algorithm (Kling et al., JRS, 2017), commercially available riboflavin (Ribo-Ker, EMAGine SA, Zug, Switzerland) and a commercially available CXL device (C-eye, EMAGine AG, Zug, Switzerland). Pre- and postoperative examinations included CDVA, refraction, Scheimpflug, and AS-OCT imaging up to 24 months after CXL. Outcome measures were the arrest of keratoconus progression at 24 months postoperatively.

Results

From the original study population (39 eyes), we examined 34 eyes for the 2-year follow-up. Stromal thicknesses ranged from 214-398 µm and the mean age was 31.62 ± 10.82 years.

Scheimpflug data showed no significant change from baseline at 24 months in minimal thickness and in Kmax, nor in ARC 3mm. No significant changes were found in CDVA, sphere, and cylinder from baseline to 2 years postoperatively. No eyes showed signs of endothelial decompensation. Mean Kmax was 59.60 ± 7.75 D at baseline and 57.89 ± 7.52 D at 2 years postoperatively (p = 0.361). Overall, the sub400 protocol successfully halted progression in 94.12% of the follow-up eyes from this series. After performing a survival analysis, the final success rate was 82.1%.

Conclusions

The ‘‘sub400’’ individualized fluence CXL protocol standardizes the treatment in ultrathin corneas and halts KC progression with a success rate of 90% at 12 months and 82% at 24 months. The sub400 protocol allows for the treatment of corneas as thin as 200 mm of corneal stroma with Kmax readings of the anterior cornea of up to 90D, markedly extending the treatment range. No signs of endothelial damage were observed