Posters

Refinement of pre-set corneal epithelial thickness and stromal ablation rate in one-step transepithelial ablations

Poster Details

First Author: L.Van Zyl AUSTRALIA

Co Author(s):    M. Goggin   P. Stewart           

Abstract Details

Purpose:

Verification and fine tuning of the effective depth and rate of ablation in customised trans-epithelial one step superficial excimer refractive surgery by the comparison of measured post-operative ablation depths with planned ablation depths calculated for both epithelium and stroma.

Setting:

2 Private Refractive Surgery Practices in urban Australia

Methods:

88 consecutive eyes in 64 patients undergoing trans-epithelial superficial refractive surgery using the iRES excimer laser system for either myopic/astigmatic or hyperopic/astigmatic refractive error between January 2012 and September 2012. Each patient had at least 3 months of post-operative follow-up. Topographic examination of all eyes was carried out pre-operatively and at 3 months post-operatively using the Precisio Scheimpflug topography system. Comparison of these two measurements yielded values for depth, volumes and rates of ablated corneal tissue. By determining the different ablation rates of stroma and epithelium, a refinement of the depth of epithelium to be removed before stromal ablation commenced was calculated.

Results:

The calculated pure stromal ablation rate was less than the average epithelium/stroma ablation rate used in planning the treatments by a factor of 0.96. The epithelial thickness constant ablation assumption used to plan removal of the epithelium in one step trans-epithelial surgery was fine-tuned as a function of the radial distance from the center to the periphery of the ablation zone, greater ablation depth being needed peripherally.

Conclusions:

Trans-epithelial one step superficial ablation can be accurately executed using the newly calculated effective stromal ablation rate in combination with a radial fine-tuned epithelial thickness ablation function. FINANCIAL INTEREST: NONE