Long term outcomes of novel customised topography-guided removal of epithelium (TREK) with topography-guided photorefractive keratectomy (T-PRK) with cross-linking

Session Details

Session Title: Presented Poster Session: Keratorefractive Surgery Results II

Venue: Poster Village: Pod 2

First Author: : G.Kundu INDIA

Co Author(s): :    A. Karunakaran   A. Sinha Roy   R. Shetty   P. Ahuja              

Abstract Details

Purpose:

In patients with early KC and adequate thickness, simultaneous topo-guided photorefractive keratectomy (T-PRK) and cross-linking (CXL) improves visual acuity and reduces higher order aberrations by regularizing the anterior corneal surface. However it is inadvisable in thinner corneas, higher grades of KC and decentered cones, where stromal tissue ablation required would be unacceptable to achieve a degree of regularization. We devised a novel tissue saving approach-Topoguided removal of epithelium (TREK) with stromal ablation (maximum 25 micron) centered over the area of highest steepening rather than the corneal apex.

Setting:

This prospective, interventional, longitudinal, comparative study was conducted at a tertiary care centre after prior ethics committee approval. We compared the visual, aberrometric and topographic outcomes of 50 TREK patients and 56 T-PRK patients with a year of follow-up post-surgery.

Methods:

For TREK, a customised elliptical ablation pattern was planned, centered at the steepest point on the anterior tangential curvature map. PTK-CAM module of the Schwind-Sirius topographer (SCHWIND GmbH, Germany) was used to perform laser ablation. Manual removal of surrounding epithelium over central 8 mm area was then followed by accelerated CXL (0.1% riboflavin for 20 mins and UV-A irradiation 9mW/cm2 for 10 minutes). In patients undergoing T-PRK, the corneal wavefront (CW) algorithm on Schwind Amaris Trans-PRK mode was used to treat the corneal surface for a modified refraction to limit stromal ablation to <40μm. Accelerated CXL was then performed.

Results:

In TREK patients, Kmax reduced by 3.62 +/- 0.9D, vertical coma by 0.56 +/- 0.3μm (25.57% decrease), RMS of higher order aberration (HORMS) by -0.66 +/-0.36μm (22.9% decrease) and TCT reduced by 35μm +/-7.5 (7.91% reduction) (P<0.05). In T-PRK patients, Kmax reduced by 4.60 +/- 0.51D, vertical coma by 0.79 +/- 0.18μm (53.02% decrease), RMS of higher order aberration by -0.80 +/-0.9μm (39.8% decrease) and TCT reduced by 63.5μm +/-3.92 (13.77% reduction) (P<0.05). In TREK, corrected distant vision improved from 0.21 to 0.16; while in the T-PRK group the CDVA improved from 0.18 to 0.06 LogMar.

Conclusions:

Our study shows that while T-PRK had better visual, aberrometric & topographic outcomes, it removed more tissue than TREK. Like T-PRK, TREK significantly reduced maximum keratometry, HORMS and vertical coma. In patients, with steeper and thinner corneas who are unsuitable for T-PRK, TREK could be a viable alternative to reduce corneal irregularity and improve visual quality.

Financial Disclosure:

None