Topography-guided transepithelial surface ablation reduces moderate to high astigmatism

Issue: October 25, 2016

Topography-guided transepithelial surface ablation improved vision and reduced moderate to high astigmatism, according to a study.

Perspective from Noel A. Alpins, MD

The retrospective study included 206 eyes; 153 eyes had myopic astigmatism and 53 eyes had mixed astigmatism.

Topography-guided transepithelial surface ablation was performed with the iRes excimer laser (iVis Technology). Corneal Interactive Programmed Topographic Ablation software (CIPTA, iVis Technology) was used to create a custom ablation plan for each eye based on subjective refraction and corneal topography.

Postoperative uncorrected distance visual acuity was better than 20/20 in 92% of eyes in the myopic astigmatism group and 83% of eyes in the mixed astigmatism group. No eyes lost more than one line of corrected distance visual acuity.

All eyes had astigmatism of 2 D or greater preoperatively. Residual refractive astigmatism was 0.5 D or less in 82.4% of eyes in the myopic astigmatism group and 56.7% of eyes in the mixed astigmatism group. Residual refractive astigmatism was 1 D or less in 97.4% of eyes in the myopic astigmatism group and 84.9% of eyes in the mixed astigmatism group.

Spherical equivalent refraction was within 0.5 D of the target in 83.7% of eyes in the myopic astigmatism group and 79.2% of eyes in the mixed astigmatism group. It was within 1 D of the target in 99.3% of eyes in the myopic astigmatism group and 94.3% of eyes in the mixed astigmatism group. – by Matt Hasson

Disclosure: The authors report no relevant financial disclosures.

Perspective

Noel A. Alpins, MD

This paper discusses transepithelial treatment in the correction of moderate and high astigmatism. The conclusion is that it is safe and effective both for myopic cylinder as well as mixed astigmatism. Although the title states the paradigm is topography driven, there is some suggestion in the paper that refractive parameters also played a part, but the proportion is unclear.

The results of eyes with myopic astigmatism (153) and mixed astigmatism (53) were successful with 83% within 0.5 D of target and 99% within 1 D. Astigmatism outcomes showed a difference vector of 0.38 D (myopic) and 0.65 D (mixed).

There was a general undercorrection of astigmatism by the iVis laser by 0.96 correction index for myopia and 0.84 for mixed. The range of alignment accuracy was from –14° to +13° (myopia) and –22° to +13° (mixed). However, contrary to what is stated, misalignment is not a cause for undercorrection as the ratio SIA/TIA is not affected.

Noel A. Alpins, MD

OSN Refractive Surgery Board Member

Disclosures: Alpins reports he owns a financial interest in Assort Surgical Management Systems.

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Source:

Chen X, et al. J Refract Surg. 2016;doi:10.3928/1081597X-20160428-01.