Laser surgeries are effective and safe, however, over the years data has accumulated about several complications of the procedures, particularly corneal ectasia. Various studies demonstrated the importance of the front layers of the cornea to keep its structure fixed. In order to correct various degrees of myopia, different thicknesses of tissue have to be removed. Therefore, it is conceivable that the risk of developing ectasia might increase depending on the depth of corneal tissue removed.

In the last few years, the Reichert Ocular Respond Analyzer (ORA) for measuring the biomechanical parameters of the cornea has been introduced. Studies demonstrated a decrease in the corneal biomechanical parameters after Laser Assisted Sub-epithelial Keratomileusis (LASEK) surgery. However, the, relation between the depth of tissue removed and the amount of change in the biomechanical parameters had not been tested yet.

To evaluate the relationship between corneal biomechanical parameters and corneal tissue ablation thickness.

Data was retrospectively collected from patient's files that underwent LASEK in private medical center – Hadassah Optimal in Haifa between January 2009 and May 2010. All patients were operated by same surgeon (AB). In our study we included patients that had at least three ORA measurements at three set periods of time; before the operation, up to 3 months postoperative and more than 3 months postoperative. We divided the patients into 3 groups depending on the refractive error and tested the effect of variable factors (Age, Total depth ablated-TDA, percent of total depth ablated-%TDA, sex, refraction). The data was analyzed by descriptive statistics and student t-test to find the relation between LASEK and the corneal biomechanical parameters.

Ninety-eight patients participated in our study, which included 98 separate eye operations. A statistically significant decrease (p < 0.001) was found in CRF, CH, IOPg after LASEK. In group 1 (refraction −0.5 to −2.99): on CH – there was a statistically significant (p < 0.05) weak-moderate effect of TDA and %TDA (Pearson coefficient of 0.4, 0.39 respectively), statistically significant (p < 0.05) effect of age. On CRF — we found a statistically significant (p < 0.05) weak-moderate effect of TDA and %TDA (Pearson coefficient of 0.36 for both factors), statistically significant (p < 0.05) effect of age. In the second group (refraction value −3 to −5.99) only on IOPg a statistically significant (p < 0.05) weak effect of TDA (Pearson coefficient of 0.33) was demonstrated. In the third group, we did not find any effect of the variable factors on the change in biomechanical properties characteristics after LASEK.

Corneal biomechanical properties influence corneal behavior in certain eye diseases. Moreover, it has been noted that operations and procedures affect these biomechanical properties of the cornea. Hence, it is of great importance to reveal factors that could affect and change such parameters.

Barbara R, Nassar A, Zadok D, Barbara Corneal Biomechanical Properties Post-LASEK for the Correction of Myopia. Int J Kerat Ect Cor Dis 2014;3(1):23-28.