Difference in profile of peripheral defocus after orthokeratology and eximer laser correction of myopia

A variety of factors that change the topography of the cornea may also induce changes in peripheral refraction. Purpose. The paper is aimed at assessing the peripheral refraction and retinal contour of myopic eyes after FS-LASIK and orthokeratological (Ortho-k) correction. Materials and methods. We examined a total of 30 patients (60 eyes) aging from 28.86 ±2.83 years which included 12 patients (24 eyes) with myopia of -5.11 ± 0.5 D and with an axial length (AL) of 25.04 ±0.33 mm before and 1 month after FS-LASIK surgery, and also included 18 patients (36 eyes) with myopia of -5.4 ± 0.24 D and AL of 25.78 ± 0.2 mm who wore ESA-DL Ortho-k lenses. The peripheral refraction of all the patients was measured using the Grand Seiko Open-field binocular autoref/keratometer and the peripheral eye length was measured using the IOL Master 500 (Carl Zeiss) at 15° and 30º nasally (N) and temporally (T), respectively, from the center of fovea. Results. The peripheral eye length measured before and after FS-LASIK as well as after Ortho-k correction was less in all peripheral zones than in the center, which corresponds to characteristics observed in hyperopic peripheral defocus. Refraction measured after FS-LASIK showed the formation of myopic defocus with a maximum at 30° from the following results: -2.49 D at T15°, -2.5 D at N15°, -6.73 D at T30°, and -7.8 D at N30°. The maximal myopic defocus after Ortho-k correction was detected in the middle periphery from these following results: -4.89 D at T15°, -5.51 D at N15°, -2.92 D at T30° and -2.4 D at N30°. Conclusions. Both procedures induced a significant peripheral myopic defocus. In the first case, the maximum values of defocus were detected in the peripheral zone (30° from the center of the fovea); in the second case, the maximal effect on the middle periphery was identified 15° from the center. Such patterns of peripheral refraction fully coincided with the specific changes in corneal topography after the two procedures. The retinal contour within 30° from the center retained the relative hyperopic defocus characteristic of intact myopic eyes // Russian Ophthalmological Journal, 2017; 1: 31-5. doi: 10.21516/2072-0076-2017-10-1-31-35.

миопия, периферическая рефракция, дефокус, периферическая длина глаза, ортокератология, myopia, peripheral refraction, defocus, peripheral eye length, orthokeratology

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