Corneal Biomechanical Changes Following Myopic and Hyperopiclaser in Situ Keratomileusis
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- Category: Vol. 85, December 2017
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Corneal Biomechanical Changes Following Myopic and Hyperopiclaser in Situ Keratomileusis, HEBA H. SAYED, AHMED H. EL-KATEB, AHMED HASSANEIN and AHMED ABD EL-BAKI
Abstract
Background: LASIK has become one of the main lines of treatment for correction of both myopia up to –9.00 to –12.00 diopters, hyperopia up to +4.00 diopters and astigma-tism up to 5.00 diopters. Although being safe, it can be complicated with a rare but visually debilitating refractive instability called ectasia. It has been recommended to perform ORA pre-operatively with the routine investigations for patients undergoing LASIK surgery. This can detect patients at risk of post LASIK ectasia in spite of normal tomographic values.
Aim: To detect changes in the Corneal Hysteresis (CH) and the Corneal Resistance Factor (CRF) after myopic and hyperopic Laser in Situ Keratomileusis (LASIK) using Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments; Buffalo, NY) and to evaluate their relationship with the Residual Stromal Bed (RSB).
Methodology: This prospective, non-randomized, non-controlled study was conducted on forty eyes of twenty one Egyptian patients. The aim of this study is all patients under-went conventional LASIK and evaluation was done pre-operatively and postoperatively at 3, 6 months, regarding: Changes in CH and CRF.
Results: The mean pre-operative CH in the myopic LASIK group was 10.65-}1.31mmHg, and in the hyperopic LASIK group it was 11.03-}1.2mmHg, with no statistically significant difference between both groups (p=0.096). The mean post-operative value of CH of themyopic LASIK group was 9.86-} 1.3mmHg, and in the hyperopic LASIK group it was 10.33-} 1.01mmHg. The mean percentage reduction in the myopic LASIK group was 7.3% and in the hyperopic LASIK group was 6%. The value of the average absolute reduction of CRFof the myopic LASIK group was 2.04-}0.62, and in the hyperopic LASIK group it was 0.58-}0.27.
Conclusion: Both CH and CRF decreased significantly after LASIK, with more reduction in the CRF in the myopic group rather than the hyperopic group.