A Next Generation Crosslinking Calculator For Titrating Ultraviolet Energy (Nxt-Uva) In Thin Keratoconic Corneas
Published 2022
- 40th Congress of the ESCRS
Reference: FPS10.10
| Type: Free paper
| DOI:
10.82333/ew8h-d764
Authors:
Tulasi Ravindra Meda* 1
, Rohit Shetty 2
, Pooja Khamar 1
, Eberhard Spoerl 3
, Sailie Shirodkar 1
1Phacorefractive,Narayana Nethralaya,Bangalore,India, 2Narayana Nethralaya,Bangalore,India, 3University Carl Gustav Carus,Dresden,Germany
Purpose
To evaluate the performance of the NXT (New generation CXL for Thin Cornea) UV-A calculator, which aids in customizing fluence to the corneal thickness for crosslinking (CXL) in thinner corneas.
Setting
Narayana Nethralaya Superspecialty Eye Hospital , Bangalore , India
Methods
The study included 84 eyes of 84 patients with progressive keratoconus and mean thinnest corneal thickness (TCT) <420µm. Corneal tomography, epithelial mapping (CSO MS39 ASOCT) and specular microscopy were done preoperatively and postoperatively. Mean TCT after de-epithelialization was entered into the custom-built web-based calculator, which gave us customized fluence time based on the chosen UV power (https://jscalc.io/calc/VmanUJD6yQ13VQQ6). The NXT UVA calculator provided fluence times for UV powers of 9 and 3 mW/cm2, which are commonly used for the accelerated protocol and for 0.1 and 0.2% riboflavin concentrations. Post-operative assessments were performed at 1 week, 1, 3, 6 and 12 months for safety and efficacy.
Results
Estimation of safety determined that there was no post operative loss of lines/visual acuity (VA) and no significant haze on densitometry .Pre-op values of K1 52.6± 4.95 , K2 57.68± 5.28, Kmax 64.71± 8.42 .Efficacy determinants demonstrated no progression – stable K1 (51.37 ± 5.55, p <0.0001), K2 (56.76± 6.15, p= 0.0002) and Kmax (63.99± 8.6 , p= 0.2 ) at 6 months and no change in cell density on specular microscopy (2707.7 ± 270.9 pre-operatively to 2641.33 ± 374.9 post-operatively, p=0.2 ). 64% had a demarcation line at 3 months at a depth of 295±71 µm. All patients were fitted with contact lenses at 3 months with VA 20/30 or better.
Conclusions
The UV “on” time needs to be titrated based on the corneal thickness, riboflavin concentration and incident intensity to minimize the risk of damage to the corneal endothelium. The NXT Calculator thus provides a easy, quick, user-friendly approach of CXL in thin corneas, with no additional tools and no risk of corneal scarring.