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A. Demesticha, H. Ginis, G. Kymionis, N. Astirakakis, I. Pallikaris; Visual Fields After Refractive Surgery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4205.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this prospective study was to evaluate the sensitivity in the peripheral visual field in patients undergoing photorefractive keratectomy for the correction of myopia.
Thirty two eyes of eighteen patients with mean ±SD age 29 ±3 years were evaluated preoperatively and at the 3 months postoperative interval following PRK for the correction of myopia (mean ±SD spherical equivalent refraction -2.75 ± 0.97D) at an optical zone of 6.5mm with the Allegretto 400 (Wavelight AG, Erlangen Germany) laser system . Evaluation of the optical fields was made using the MEDMOND M700 (Medmont international Pty Ltd, Australia) visual fields analyzer using a full threshold procedure with stimulus size: Size III (26 arcmin) and Background Illumination :10cd/m2 . Measurements were performed under cycloplegia . For the central degrees of the optical field (1-22 degrees) the refracted error was completely corrected . The marked cycloplegic effect necessiated the use of a+3D auxillary lenses to cover the distance of the stimulus (33cm)
The detection threshold value exhibited a decrease ranging from 0.5 to 9 DB (mean ±SD threshold decrement 2.64518 ±1.85 DB) for the periphery of the optical field (30 to 40 degrees). This change was statistically significant (p= 3.97912E-09 ). In particular in peripheral 40 degrees of visual field the threshold MS changed with a depression of 3.86258 ±2.65DB (p=2.51619E-09 ) .No statistically significant difference was observed for the central visual field (0-22 degrees).The results of this study demonstrate that the effect of defocus on threshold retinal sensitivities were negligible at 30 degrees or more from fixation.
The loss of peripheral visual fields following refractive surgery may be attributed to the deteriorated retinal image quality in the peripheral visual field. A mathematical model is proposed to employ optical calculations of the PSF in the periphery of post PRK eyes and to establish a relationship between optical deterioration and the associated change in sensitivity. In clinical practice, a visual field loss may occur due to disease or disorders of the eye, optic nerve, or brain. For example in case of glaucoma, where the threshold in the midperiphery is evaluated, it is important to take into account whether the patient has undergone a refractive surgery in the past.
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