Dr. Shruti Kochar, K17834, Dr.Natasha Pahuja, Dr. Rohit Shetty, Dr. Abhijit Sinha Roy
Presenting Author: Dr Shruti Kochar Maru
Co- Authors: Dr Natasha Pahuja, Dr Rohit Shetty, Arkasubhra Ghosh, Abhijit Sinha Roy
Institute: Narayana Nethralaya Bangalore, India
No other author has any financial or proprietary interests to declare
Introduction:
Keratoconus is a corneal disease characterized by progressive thinning and protrusion of cornea.1In patients with progressive keratoconus with a clear central cornea and thinnest corneal thickness >400 microns, corneal cross-linking (KXL) can reduce the risk of progression.2 Keratoconus is a localized disease hence the treatment should be localized and not uniform.3 However, the mechanisms underlying the focal disease and the effect of the molecular factors on treatment outcomes remain unknown.
Purpose:
To study clinical and biomechanical outcomes of topography-guided customized corneal cross-linking and its relationship to cellular biomarkers.
Methods:
We conducted prospective study on 17 keratoconic eyes that underwent novel topography-guided cross-linking (Avedro Inc., USA) using a programmable beam pattern with differential surface dose at location of cone. A patient specific UV beam was designed centered on the cone. Energy delivered varied from 10 J/sq. cm in the center to 3 J/sq. cm in periphery. Maximum area treated was 8mm. Epithelium was analyzed for biomarkers. Topography and deformation amplitude were measured at 6 months.Eyes with Progressive keratoconus having corneal thickness >370 microns at the thinnest location were included. Exclusion criteria included central or paracentral scarring, concurrent corneal infections and Other ocular co-morbidities. Images were captures on Pentacam HR (Oculus Optikgeräte GmbH). Image capture onPentacam HR were exported to the KXL-II machine. The advantage of KXL II being programmable illumination measurements pattern, real time eye tracking and real time riboflavin dosimetry.
Outcome measures were assessed using-
- Mean residual spherical
- Equivalent-MRSE
- Flat keratometry- K1
- Steep keratometry- K2
- Maximum keratometry Kmax
- Lower order aberration- LOA
- Higher order aberration- HOA
- Total aberration- TOA
- Mean deformation amplitude- DA
Results:
Mean MRSE reduced by 0.53±0.35D (p=0.15). Mean keratometry reduced by -0.25±0.23D (p=0.30). The mean deformation amplitude reduced significantly by -0.04±0.02 (p=0.025) suggesting biomechanical improvement. We also studied the epithelium of the cone area in these 17 eyes collected during the surgery. Eyes were categorized into good prognosis (MRSE difference post-op minus pre-op ≥ 0 and bad prognosis if its < 0).Trend shows increased expression of LOX (Lysyl oxidase)vin patients with good outcomes as compared to the patients with bad outcomes. Whereas TNFα (Tumor Necrosis Factor alpha) expression is less in patients with good outcomes as compared to the patients with bad outcomes. Expression of Collagen was found similar in the both groups. Keratoconus patients exhibit reduced LOX mRNA expression levels in corneal epithelial cells.
Conclusion:
Customized beam profile based on topography showed improvement in Refractive and Keratometric indices at 6 months though not statistically significant. Corneal Biomechanics showed significant reduction in Deformation amplitude post treatment. Biomarker analysis from epithelium of cone and periphery preoperatively, can predict postoperative outcomes for such patients
References:
1) Gordon-Shaag, A, Millodot, M, Shneor, E et al., The genetic and environmental factors for keratoconus. BioMed research international 2015; 2015: 795738.
2) Arnalich-Montiel, F, Alio Del Barrio, JL, Alio, JL, Corneal surgeryin keratoconus: which type, which technique, which outcomes? Eye and vision 2016; 3: 2.
3) Seiler, TG, Fischinger, I, Koller, T et al., Customized Corneal Cross-linking: One-Year Results. American journal of ophthalmology 2016; 166: 14.