A Clinical Study Of Contrast Sensitivity And Stereoscopic Vision In Myopic Eyes Before And After Laser In Situ Keratomileusis

A Clinical Study of Contrast Sensitivity and Stereoscopic Vision in Myopic Eyes before and after Laser in Situ Keratomileusis It is necessary to evaluate vision quality of myopic patients after laser in situ keratomileusis(LASIK) as LASIK gradually become a method of myopic treatment. The sense and depth perception in visual function are important manifestation of visual quality. So we have evaluated and analysed contrast sensitivity(CS)and stereoscopic vision before and after LASIK.Objective: To find out the change of CS and stereoscopic vision in myopic eyes before and after LASIK and increase clinical application value of vision quality in terms of forming sense and depth perception of visual function.Methods: One hundred and seventy-four myopic and astigmatic patients from June 2002 to Febuary 2004 were examined for the following items: normal visual acuity, optometry, intraocular pressure,slit lamp and corneal topography measurement .CS and near,far distance stereoscopic vision with Optec3500 Vision Tester and Titmus Stereo Tests under the nighttime, nighttime & periglare, daytime,daytime & periglare conditions before LASIK and in 0.5,1,3,6,12 months after LASIK.Result: 1. Preoperationaly under the nighttime condition and the nighttime & periglare condition at high spacial frequency the CS of low ,medium and high myopia was different apparently; under the daytime condition at 18c/d and the daytime & periglare condition at high spacial frequency the CS of low and high myopia increased apparently. 2. CS was depressed for myopic eyes at 0.5 months postoparation under the nighttime,nighttime & periglare,daytime,daytime & periglare conditions , especially the high mypia at low and media spacial frequency under the nighttime,nighttime & periglare conditions from 1 to3 months after LASIK, and at high spacial frequency from 3 to 6 months after LASIK(P<0.05).3. The main field of the depression of CS was at medial spacial frequency.4. The recovery of the CS to the preoperative levels for low and media myopic group eyes was found between 3 and 6 months after LASIK ,and visual quality had slightly increased between 6 and 12 months after LASIK. For high myopic eyes the recovery of the CS to the preoperative levels was found at 12 months of postoperation,but under the nighttime & periglare condition the CS was still below the preoperative levels. 5. The central near and far distance stereoscopic vision improved apparently.For anisometropic patients in postoperation compared with preoperational wearing glasses the central near and far distance stereoscopic vision was far more increased.Discussion: The CS and stereoscopic vision is the main content of the visual function in form sense and depth perception of visual function ,which reflect the visual quality of the myopic eyes after LASIK in form of the most fundamental and highest grade monocular and binocular visual function. 1. The feature of CS of the myopic patients wearing glasses before LASIK.Compared with that of low and high myopia,the CSF curve of high myopia decreased apparently at high spacial frequency,because it was CSF curve descended as diopter increased as pathological change of retina more apparent and visual functional lesion more severe.2.LASIK and CS.The CS in the early postoperational period of the keratorefraction depressed and gradually recovered .The descent of medial spatial frequency of CSF curve clarified that the level of the CS in medial spacial frequency was in directly related with the quality of central visual function.The recovery of CS of the high myopia was at 12th month in postoperation,especially under the nighttime & periglare condition need longer,so the full recovery of coneal structure and function in high myopia eyes maybe need twelve months or even longer. 3. LASIK and stereoscopic vision. It was the examination to overall evaluate the highest grade binocular visual function of the operational eyes . LASIK corrected the refraction of the eye to reduce the effect of shrinking body image that project to th...