Unusual corneal topography and insufficient corneal thickness remain the most common exclusion factors for corneal refractive surgery, according to a new retropective study that examined patient criteria for LASIK and PRK, published in the October 2014 Cornea.1 

Researchers from the Cole Eye Institute in Ohio and the University of Sao Paulo in Brazil evaluated 1,067 candidates—519 males and 548 females—for primary refractive surgery procedures over a five-year period. 

Prospective patients were considered if they met the following general criteria: age 18 years or older, stable refraction for at least one year, myopia ≤10.5D, hyperopia ≤4.50D, astigmatism ≤6.00D, central corneal thickness >480μm measured with ultrasonic pachymetry, expected residual stromal bed >300μm after LASIK, and >400μm corneal thickness after PRK or LASIK. Additionally, prospective patients could not be pregnant or lactating, have corneal abnormalities indicative of keratoconus or other corneal ectatic disease, or exhibit ocular pathology such as an active infection.

Of the initial candidates considered, 61.6% (657 patients) underwent refractive surgery. Based on the criteria, LASIK was selected as the better option for 556 of these patients, while PRK was considered better for 106 patients (e.g., for those with thin corneas, high risk of injury or simple patient preference)

Of the 410 patients who did not undergo refractive surgery, 276 choose to defer the procedure while 134 were deemed medically contraindicated to both LASIK and PRK, with abnormal corneal topography (34.3%) and low or insufficient corneal thickness (23.1%) the most common reasons for exclusion. This is in contrast to previous studies, based only on LASIK surgery with mechanical microkeratomes, which pinpointed insufficient corneal thickness to be the most common reason.

The study also identified cataract (9.7%) and high myopia (10.5%) as other common exclusion factors, as well as high hyperopia (3.7%), the need to wear reading glasses after surgery (3.7%) and severe dry eye unresponsive to treatment (3.7%).

1. Torricelli A, Bechara S and Wilson S. Screening of refractive surgery candidates for LASIK and PRK. Cornea 2014;33:1051-1055.