Fluence Customised Titration Of Ultraviolet Energy For Extremely Thin Keratoconic Corneas (<350 Microns) Using A Next Generation Cross-Linking Calculator
Published 2023 - 41st Congress of the ESCRS
Reference: PP14.08 | Type: Free paper | DOI: 10.82333/ev83-pv68
Authors: Akash Jeevan Jain* 1 , Rohit Shetty 2 , Pooja Khamar 1 , Abhijit Sinha Roy 3 , Raghav Narasimhan 3
1cataract and refractive,Narayana Nethralaya,Bengaluru,India, 2Cornea Refractive,Narayana Nethralaya,Bengaluru,India, 3GROW Labs,Narayana Nethralaya,Bengaluru,India
Purpose
To evaluate the performance of customised fluence in cross-linking protocols for thinner corneas of less than 350 microns thickness using the NXT (New generation CXL for Thin Cornea) UV-A calculator.
Setting
Narayana Nethralaya Superspeciality Eye Hospital, Bengaluru , India
Methods
The study included 54 eyes with progressive keratoconus and mean thinnest corneal thickness (TCT) <350μm. Corneal tomography, epithelial mapping and specular microscopy were done pre and post-operatively. Mean TCT after de-epithelialization was entered into a custom web-based calculator, which gave customized fluence time for UV powers of 9 3 mW/cm2 which is used for accelerated CXL. Post-operative tests were done at 1 week, 1, 3, 6 & 12 months. Structural integrity of collagen fibrils was studied using polarisation-sensitive optical coherence tomography (PS-OCT). Pre-operative and post-operative topography and PS-OCT scans were taken and corneal fibril distribution images were generated using phase retardation (PR) maps.
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 were 52.6± 4.95 , K2 57.68± 5.28, Kmax 64.71± 8.42 .Efficacy determinants demonstrated decrease in K1 (51.37 ± 5.55, p <0.0001), K2 (56.76± 6.15, p= 0.0002) and stable 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. The PS-OCT maps showed strengthening of collagen fibrils post-operatively. PR maps showed stability in the birefringence till 12 months following the CXL
Conclusions
Customised fluency for thin cornea may potentially minimise the need of Corneal transplant. The NXT Calculator thus provides easy, quick, user-friendly approach of CXL in thin corneas, with no additional tools and no risk of corneal scarring.