prevalence of astigmatism and its determinants in a rural population of Iran: the "nooravaran salamat" mobile eye clinic experience

The prevalence of astigmatism, and the astigmatic axis, and their determinants were evaluated in a rural population of Iran. In a cross-sectional study conducted from May to August 2011, 13 villages in the vicinity of the city of Khaf in northeast Iran were investigated in this study. All the examinations including visual acuity, refraction, slit-lamp biomicroscopy and fundoscopy were performed in a Mobile Eye Clinic. Written informed consent was obtained from all participants. Only phakic eye that could be reliably refracted without a previous history of ocular surgery were included. Out of 2635 participants who were screened, 2124 were analysed for this study of whom 52% were female. The prevalence of astigmatism was 32.2% [95% confidence intervals [CI]: 30.2-34.2]. Astigmatism significantly increased from 14.3% in the under 15-year-old age group to 67.2% in the age group of over 65-years old [P < 0.001]. The prevalence of With-The-Rule [WTR], Against-The-Rule [ATR], and oblique astigmatism was 11.7%, 18.1%, and 2.4%, respectively. ATR significantly increased with age [P < 0.001]. The mean corneal astigmatism was 0.73 D which linearly increased with age [P < 0.001]. Attention must be paid to astigmatism in rural areas due to the high prevalence. Further studies are suggested to discover the role of the environmental and genetic factors. It seems that environmental and occupational factors in the villages cause a significant increase in the prevalence of astigmatism with age. A high percentage of participants had ATR astigmatism, which was more common at older ages.

Pattern visual evoked potentials in patients with type II diabetes mellitus

To evaluate cortical and retinal activity by pattern visual evoked potentials [PVEP] in patients with type II diabetes mellitus. PVEP was recorded in 40 diabetic patients including 20 subjects with nonproliferative diabetic retinopathy [NPDR] and 20 others without any retinopathy on fundus photography, and compared to 40 age- and sex-matched normal non-diabetic controls. P100 wave latency was significantly longer in diabetic patients as compared to normal controls [P<0.001]; both diabetic subjects without retinopathy and those with NPDR had significantly longer P100 latency than controls [P<0.001 for both comparisons]. There was significant reduction in N75 [P=0.037] and P100 [P=0.001] amplitudes in diabetic subjects. No correlation was observed between VEP amplitude or wave latency, and the level of glycemia or duration of diabetes mellitus. Increased PVEP latency may be a sign of retinal ganglion cell damage which takes place before the appearance of the first ophthalmoscopically detectable signs of diabetic retinopathy. PVEP may be considered as a method for detecting prediabetic retinopathy and has the potential to reduce diabetic complications.

Importance of including refractive error tests in school children's vision screening

This study determined the importance of including tests for refractive errors in vision screening. In this cross-sectional study, we performed a random cluster sampling of schoolchildren in the city of Dezful, Iran. After sampling and obtaining informed written consents from their parents, children underwent examinations at the school sites. Students underwent tests of visual acuity, cover tests and cycloplegic refractions. Elementary and middle school students who had a visual acuity of 20/20 or better, in both eyes were included in the study. From 3673 elementary and middle school students, 2957 [80.5%] had 20/20 vision or better. Of these, 16.1% [95% confidence interval [Cl]: 14.8 - 17.4] were ametropic, 0.4% had myopia and 10.1% had hyperopia. Mean sphere in those with hyperopia was +2.6 +/- 0.7 [range: +2.0 to +7.28] diopter [D]. Astigmatism was detected in 6.6% and the mean cylinder was -0.9 [range: -0.75 to -3.25] D. The rate of anisometropia was 1.5% [95% Cl: 0.8 - 2.0]. Screening results of 20/20 vision for schoolchildren does not necessarily indicate normal eye status because hyperopia and astigmatism may still be sources of visual discomfort. To identify these cases and increase the sensitivity of screening tests, measurement of refractive errors by cycloplegic refraction tests might be included in vision screening

[Evaluation of relationship between contrast sensitivity, color vision and visual acuity in diabetic patients with and without retinopathy]

To investigate the discriminative ability of contrast sensitivity [CS], color vision and log MAR visual acuity [VA] in detecting functional losses in diabetic participants with and without retinopathy comparing to the control group. In this cross sectional study in 1388 we examined 105 patients in Mashhad Khatam- Al-Anbia Eye Hospital including 70 diabetic patients [35 with retinopathy and 35 without retinopathy] with 35 control group. Contrast sensitivity was examined by means of CSV-1000 E at 3, 6, 12 and 18 cpd respectively. Color discrimination ability was measured with the Farnsworth D-15 test and log MAR VA by Snellen chart. Contrast sensitivity was significantly lower in the diabetic eyes with retinopathy than in the normal eyes in all spatial frequencies. Comparing to the control group, there was a statistically significant CS loss in spatial frequencies of 3, 6, 18 cpd in the diabetic eyes without retinopathy [p<0.05]. The mean log MAR VA and color vision abnormalities were significantly higher in the diabetic eyes with retinopathy than in the normal eyes or the diabetic eyes without retinopathy [p<0.001]. The sensitivity and specificity of the CS test in 6 cpd were 71% and 82% which were significantly higher than other spatial frequencies. The sensitivity and the specificity of the color vision test and VA [log MAR >/= 0.05, Snellen

Prevalence and risk factors of refractive errors among school children in Mashhad, 2006-2007

To determine the prevalence of refractive condition and its risk factors among students in Mashhad. A total of 2510 students representing a cross-sectional of the population of Mashhad were sampled using random cluster sampling strategy. Primary and middle school students underwent cycloplegic refraction. The refractive errors of high school students were measured using non-cycloplegic autorefraction. Myopia was defined as spherical equivalent [SE] of -0.5 diopter [D] or more, and hyperopia was defined as SE of +0.5 diopter [D] or more, and astigmatism of 0.75 cylinder diopter or greater. Examination was carried out in the school using standardized testing protocols. 2150 students [group 1: 1163 primary and middle school, group 2: 947 high school students and 13 missed data] participated. The prevalence of refractive errors in the 1st group was: myopia=2.4%, hyperopia=87.9%, astigmatism=9.8% and anisometropia=3.0% [SE difference at least 1.00 D], and in the 2nd group myopia=24.1%, hyperopia=8.4%, astigmatism=11.8% and anisometropia=5.6%. There was significant difference in refractive errors between girls and boys [P<0.001]. In primary and middle school prevalence of myopia increased with age [OR=1.3 95% CI: 1.03 to 1.7 and P=0.013]. The prevalence of refractive errors among students in Mashhad is high. Effective detection and treatment of these refractive errors is expected to reduce the incidence of amblyopia and strabismus and also can prevent substantive effects on academic performance