Posters

Percent Tissue Altered (PTA) Reliability as Unique Parameter for Post-LASIK Ectasia Detection

Poster Details

First Author: C.Rocha de Lossada SPAIN

Co Author(s): J. Sánchez-González   J. García-Madrona   F. Alonso Aliste   A. Saad   S. Figueroa Ardila   E. Colmenero-Reina     

Abstract Details

Purpose:

To evaluate percent tissue altered (PTA) formula efficacy, safe, predictability and stability in post-LASIK (laser-assisted in-situ keratomileusis) ectasia risk. We also analyze spherical aberration (SA) and root mean square (RMS) between higher-PTA (>; 40%) and lower-PTA (<; 40%) groups.

Setting:

Retrospective, observational and longitudinal study. All surgeries were performed at the facilities of the Vistalaser ® Ophthalmology Clinic, Malaga, Spain.

Methods:

One hundred and ninety-three eyes from 104 patients underwent femtosecond-LASIK in low and moderate myopia. Seventy-eight eyes were included in higher-PTA (>; 40%) group while 115 eyes were included in lower-PTA (<; 40%) group. Spherical manifest refraction, cylinder manifest refraction, logMAR and Snellen previous corrected distance visual acuity (CDVA), posterior uncorrected distance visual acuity (UDVA), anterior face Baiocchi Calossi Versaci index (BCVf) and posterior face (BCVb), central corneal thickness (CCT), estimated residual stromal bed (RSB), SA and RMS were reported.

Results:

In higher-PTA, 97% of eyes reported UDVA 20/20 or better and in lower-PTA all eyes obtained 20/20 or better. No group lost lines of VA. Higher-PTA obtained a regression line of y = 1.02 x + 0.57 and lower-PTA y = 0.92 x + 0.19. Higher-PTA group obtained 55% of eyes within ± 0.50 D and 90% within ± 1.00 D and lower-PTA group obtained 63% of eyes within ± 0.50 D and 90% within ± 1.00. Both groups obtained a regression refraction of 0.50 D or more in 36% and 31% of eyes in higher-PTA and lower-PTA groups, respectively.

Conclusions:

Percent tissue altered index could not be taken as unique variable in post-LASIK ectasia risk factor. Ectasia susceptibility screening should integrate tomography and biomechanical variables in order to help us to decide any refractive treatment choice and increasing refractive surgery safety.

Financial Disclosure:

... receives consulting fees, retainer, or contract payments from a competing company