ABSTRACT
Background The evaluation of visual function after laser in situ keratomileusis(LASIK) mainly focuses on the study of contrast sensitivity funetion (CSF).However,CSF measurement is a subjective method and therefore has a limiting in application.A point spread function (PSF) is becoming a study topic because of its objectivity in assessing visual quality.Objective Present study was to evaluate the change of the modulation transfer function (MTF) of eyes and compare the optical and visual quality of human eyes after LASIK.Methods Thirty-six patients(72 eyes) were included in this study.The patients were divided into low myopia(-2.72±0.52 D),moderate myopia (-4.89+0.80 D) and high myopia (-8.00+0.98 D) groups according to the spherical equivalent (SE)diopter before the sugery.The uncorrected visual acuity (UCVA),best corrected visual acuity (BCVA) were examined before and after operation,and PSF data was obtained with Topoeon PSF-1000 analyzer under the 3.0 mm and 6.0 mm pupil size conditions.The follow-up visits of the patients were scheduled at the 7th days,1 st and 3rd months.Written informed consent was obtained from each patient before this study. ResuIts The MTF values among the three refractive groups were significantly different between 3 mm and 6 mm pupil preoperatively (P＜0.05).Under the condition of 3 mm pupil size,the MTF values in the spatial frequencies of 2.98 cpd and 14.88 cpd were significantly declined in different time points after operation in comparison with preoperative ones (P＜0.05).However,the MTF changes had no statistical significance in the spatial frequencies from 18.85-37.70 cpd among various time points(P＞0.05).Under the condition of the 6 mm pupil size,MTF values in low and moderate myopia groups were reduced after operation in comparison with before operation at the spatial frequencies from 2.98-7.44 cpd(P＜0.05),however,there were no obvious difference was found in the spatial frequencies of 9.42-37.70 cpd(P＞0.05).The MTF values of high myopia group was decreased significantly at all spatial frequencies(P＜0.05).The MTF values improved gradually as the prolong of time after operation but was still lower at the 3rd postoperative month than that of preoperation. Conclusion The postoperative visual quality is associated with refractive power and pupil diameter.PSF is a feasible method in assessing the early visual quality after LASIK.
ABSTRACT
Objective To explore the cataract surgery quality on blindness prevention and postoperative problems in village in short period. Design Population-based survey. Participants 251 cases(254 eyes) received operation and 131 cases(134 eyes)were surveyed 6-month postoperatively. Methods Patients were examined 6-month after the small incision extracapsular cataract extraction and intra ocular lens(IOL) implantation. Examinations were conducted by a special oculist including far vision, near vision, external in- spection, anterior segment, posterior segment, intraocular pressure. Main Outcome Measures Visual acuity, intraocular pressure, diopter, eye complications of surgery. Results Naked far vision of the operated eye more than or equal to 0.3 was 41.8%, naked far vi- sion of the eye more than or equal to 0.05 was 82.8%; corrected far vision more than or equal to 0.3 was 64.2%, corrected far vision more than or equal to 0.05 was 92.3%. Naked near vision more than or equal to 0.1 was 79.9%, corrected near vision more than or e- qual to 0.1 was 85.8%. The main postoperative complications were ametropia, posterior capsule opacification(PCO), deformed pupil, pupil displacement, pigments of IOL, eccentric IOL and intraocular hypertension. The chief reasons of eyes that could not be recovered were vitreous, retina or optic nerve diseases, the key factors that caused living vision less than 0.3 were ametropia, PCO, the disease of vitreous, retina and optic nerve. Conclusions The serious complications affecting the surgery result are limited in a low range. The most important factors of the eye corrected far vision less than 0.05 are the vitreous, retina and optic nerve diseases. In order to improve the visual sight, we should add equipment to calculate the IOL diopter accurately.