To prospectively review current understanding and future trends of screening for keratectasia risk prior refractive laser vision correction (LVC).
Progressive keratectasia is an uncommon but severe complication of LVC. Preoperative ectatic corneal disease is the most important risk factor. Screening for subclinical ectasia relies on proper interpretation of advanced diagnostic technologies, including front surface corneal topography, three-dimensional tomography, and biomechanical assessments.
Studies involving eyes with normal and stable corneas, compared to eyes with frank ectatic diseases and to eyes with normal topography from patients with very asymmetric ectasia, allow for developing advanced methods and testing its sensitivity. However, the ideal study populations for testing the sensitivity and specificity of ectasia risk assessments are respectively the preoperative of cases that developed ectasia and the ones with stable outcomes after LVC. Young age and low thickness are surrogates of corneal biomechanics, which may be replaced as risk factors by direct measurements. Keratectasia may also occur due to the surgical impact on corneal structure or due to significant trauma postoperatively. Percentage tissue altered higher than 40% is a more sensitive parameter than a fixed value for minimal residual stromal bed of 250 µm. However, the biomechanical impact from surgery is related to the region and number of lamellae that are severed, so that flap thickness and geometry should play a more relevant role, which is in agreement with finite element simulations. Artificial intelligence methods allow for combining parameters, which significantly enhance the accuracy for detecting ectasia risk.
An enhanced screening approach for preventing keratectasia should consider both preoperative patient-related data and procedure-related parameters to individually characterize ectasia susceptibility or predisposition.
Keratectasia is an uncommon, however, severe complication of LVC. Although prevention is the best strategy, an individualized enhanced ectasia screening approach for ectasia risk assessment prior to LVC procedures should integrate patient-related (individual ectasia susceptibility) and procedure-related parameters (biomechanical impact).
How to cite this article
Ambrósio Jr R, Belin MW. Enhanced Screening for Ectasia Risk prior to Laser Vision Correction. Int J Kerat Ect Cor Dis 2017;6(1):23-33.