Refractive change in response to acute hyperbaric stress in refractive surgery patients

Purpose: To illustrate the advantages and limitations of Small Incision Lenticule Extraction (SMILE) over Laser Assisted Intrastromal Keratomileusis (LASIK) in the correction of myopia and myopic astigmatism. Materials and methods: The two procedures are analysed and compared for the technical aspects. While LASIK directly depends on the laser efficacy to get the refractive change, SMILE only depends on the computer ability to design the refractive lenticule. The loss in precision taking place in the peripheral cornea with LASIK is not possible with SMILE. Tissue consumption and postoperative dry eye are also lower with SMILE. Procedure abortion has less consequences with SMILE. From a clinical point of view, refractive and visual results with SMILE are similar as those of Wavefront Optimized and Wavefront Guided LASIK, but re-operations are easier after LASIK than after SMILE. Conclusion: When indicated, SMILE is better than LASIK from a technical and procedural standpoint and is equal to Wavefront Lasik as for the obtained results. LASIK is still more versatile and it is better for re-operations.

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New Modified Equation of Contact Lens Method in Determining Post Myopic Laser Refractive Surgery Corneal Power

IIUM Medical Journal Malaysia ◽

10.31436/imjm.v15i1.408 ◽

2020 ◽

Vol 15 (1) ◽

Author(s):

Md Muziman Syah MM ◽

Mutalib HA ◽

Sharanjeet Kaur MS ◽

Khairidzan MK

Keyword(s):

Contact Lens ◽

Refractive Surgery ◽

Comparison Method ◽

Mean Difference ◽

Corneal Power ◽

Significant Difference ◽

Refractive Change ◽

The Mean ◽

Laser Refractive Surgery ◽

Modified Equation

Introduction: The purpose of this study was to derive a modified equation for contact lens method (CLM) in calculating post myopic laser refractive surgery corneal power. Methods: A total of 93 subjects who underwent myopic laser refractive surgery at IIUM Eye Specialist Clinic were recruited. The accuracy of postoperative corneal power using the standard CLM and newly-derived contact lens modified method (CLMmod) were compared to the standard comparison method ; the historical method (HM). The CLMmod equation was derived by adjusting postoperative corneal power of CLM according to amount of refractive change. Results: The mean postoperative corneal power using standard CLM was significantly higher than HM (mean difference: -0.24 D, p < 0.001). Fifty seven percent (n = 53 eyes) of the standard CLM results were within ±0.50 D of HM results. The difference between postoperative corneal power using standard CLM and HM increased significantly with the amount of refractive change (r = 0.835; p < 0.001). The mean postoperative corneal power of CLMmod showed that there was no statistical significant difference compared to the HM results (mean difference: 0.00 D, p= 0.964). Eighty eight percent (n = 82 eyes) of the CLMmod results were within ±0.50 D of HM results with improvement of 31% from the standard CLM results. Conclusion: The CLMmod equation provides more accurate calculation in determining post myopic laser refractive surgery corneal power. In near future, this modified equation can be used as an alternative equation to calculate postoperative corneal power when the preoperative data is unavailable.

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