To evaluate the efficacy, safety, predictability and stability of the percent tissue altered (PTA) formula in post-LASIK (laser-assisted in situ keratomileusis) ectasia risk assessment.
One hundred and ninety-three eyes from 104 patients with low to moderate myopia that underwent femtosecond LASIK were included in this retrospective, observational and longitudinal study. Seventy-eight eyes were classified in the higher-PTA (> 40%) group and 115 eyes in the lower-PTA (< 40%) group. Spherical manifest refraction, cylinder manifest refraction, logMAR and Snellen previous corrected distance visual acuity (CDVA), 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), spherical aberration (SA) and root mean square (RMS) were reported. All patients were followed up for 4 years.
In the higher-PTA group, 97% of eyes reported UDVA 20/20 or better, and in the lower-PTA group, all eyes achieved 20/20 or better. No group reported decreased visual acuity. The higher-PTA group obtained 55% of eyes within ± 0.50 D and 90% within ± 1.00 D; and the lower-PTA group obtained 63% of eyes within ± 0.50 D and 90% within ± 1.00 D. Both groups showed a refraction correction of 0.50 D or more in 36% and 31% of eyes, in the higher-PTA and the lower-PTA groups, respectively.
Percent tissue altered index should not be considered as a unique variable in post-LASIK ectasia risk assessment. 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.
About The Expert
Carlos Rocha-de-Lossada
- Department of Refractive Surgery and Anterior Segment, Vistalaser Clinic, Málaga, Spain.
- Department of Ophthalmology, Clinic Barcelona Hospital, Barcelona, Spain.
- Department of Ophthalmology, Regional University Hospital of Málaga, Málaga, Spain.
José-María Sánchez-González
- Department of Physics of Condensed Matter, Optics Area, University of Seville, Reina Mercedes Street, 41012, Seville, Spain. jsanchez80@us.es.
- Department of Ophthalmology, Tecnolaser Clinic Vision, Seville, Spain. jsanchez80@us.es.
Rahul Rachwani-Anil
- Department of Ophthalmology, Regional University Hospital of Málaga, Málaga, Spain.
Juan-Luis García-Madrona
- Department of Refractive Surgery and Anterior Segment, Vistalaser Clinic, Málaga, Spain.
- Department of Refractive Surgery and Anterior Segment, Ocular Health Clinic, Seville, Spain.
Federico Alonso-Aliste
- Department of Ophthalmology, Tecnolaser Clinic Vision, Seville, Spain.
Sandra Figueroa-Ardila
- Department of Refractive Surgery and Anterior Segment, Vistalaser Clinic, Málaga, Spain.
Elvira Colmenero-Reina
- Department of Refractive Surgery and Anterior Segment, Vistalaser Clinic, Málaga, Spain.
References
PubMed