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Abstract farsi

Methods: The study was a cross sectional with the element of analysis which was carried out in a primary school of the Amara city. A total of 768 children were selected randomly from 76 primary schools (urban rural, male and female schools) by cluster sampling according to the geographic area of health districts and their primary health care centers. Each child was examined for visual acuity (both uncorrected and best corrected) dry and cyclo- refraction. 

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Background and Objective: Glare can affect vision in normal and abnormal individuals. It seems that threshold and normal values of glare have been less mentioned in various sources. The aim of this study was to determine acuity preserve in glare situation in normal subjects. 
Methods: 48 subjects (96 eyes) aged 18 to 25 years with normal visual acuity, and without any refractive error participated in this study. The acuity preserve in glare situation was measured at different light intensity conditions with Metro vision glare test at different luminance and visual field.
Results: Glare source in each luminance at the nasal side may show better acuity preserve in glare situation. The maximum score for nasal and temporal source for 1 cd/m2 condition was 57.398 and 51.282 respectively. The same situation was seen for 5 cd/m2 (P<0.001). However, in glare for luminance background of 1 cd/m2, and 5 cd/m2 were significantly different (P<0.001).  The acuity preserve in glare situation for 5 cd/m2 background was higher than 1 cd/m2 luminance in both temporal and nasal sides.
Conclusion: Acuity preserve in glare situation in luminance of 5cd/m2 in both temporal and nasal was more than1 cd/m2. Acuity preserve in nasal glare situation was more than temporal glare situation.
 

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Background and Objective: This study investigates stereopsis and its correlation with refractive errors in Iranian 7-year-old schoolchildren.
Methods: This cross-sectional study included 3,675 first-grade primary school students in seven cities of Iran. The subjects were randomly selected and evaluated after obtaining an informed consent letter from their parents. There were two inclusion criteria: no systemic diseases and no medication use. Refractive errors were examined with an auto refractometer and stereopsis was measured using the TNO test. Data were analyzed by SPSS 21 and using independent t-test, ANOVA, and post hoc tests.
Results: The results of the present study showed that the rate of stereopsis in all students was 43.97±11.75 arcsec and there was a significant difference between the mean of stereopsis in females (43.30±10.62 arcsec) and males (44.59±12.66 arcsec) (P<0.001). There was also a significant difference between different types of refractive errors (myopia, ametropia, hyperopia) and stereopsis (P=0.001).
Conclusion: According to the results of the present study, girls had a better stereopsis rate than the boys. Also, after correction of refractive errors, stereopsis was not the same value in different refractive states, which could be an indication of more attention to stereopsis testing as an indicator of binocular vision performance.

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Objective: To determine visual skills in primary school children with poor performance in reading and writing.
Methods: This cross-sectional study was conducted on 28 poor-performances in reading and writing students from 600 schoolchildren, based on their teacher's score and 14 control children in second to sixth grade in one of the primary schools of Tehran. Visual acuity, refractive error, distance and near horizontal heterophoria, amplitude and facility of accommodation, amplitude and facility of vergence were measured in all subjects of both groups.
Results: Statistical comparison showed a higher hyperopia (p <0.001) and astigmatism (p <0.05) in the study group. Facility of accommodation and vergence showed lower values in the study (p < 0.001). The near exophoria was significantly greater in the study group (p<0.001).
Conclusion: This study indicates that children with poor performance in reading and writing had difficulty in visual skills. Management of visual problems in children with poor reading and writing performance should be considered.

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Background and Objectives: Keratoconus is a non-inflammatory asymmetric corneal degenerative disease characterized by the steepening and distortion of the cornea. In this disease, irregular astigmatism makes the subjective refraction difficult. Using the Pentacam, we aimed to determine the corrective astigmatism of the spectacle.
Methods: The subjective refraction and Pentacam imaging were performed for 317 keratoconic patients who referred to the Salouti Eye Clinic, Shiraz, Iran. Then, the astigmatism values obtained with subjective refraction were compared with the values of anterior and posterior corneal surface astigmatism obtained with the Pentacam imaging.
Results: The mean age of 317 keratoconic patients was 29.81 years (range: 15 to 45 years). The minimum, maximum, and average astigmatism of the corneal front surface were 0.3, 16.8, and 3.21 diopters, respectively. Also, the minimum, maximum, and average astigmatism of the corneal back surface were 0, 2.8, and 0.67 diopters, respectively. Moreover, the P value was lower than 0.001 in the regression analysis of the subjective refraction for both the power and axis of the cylinder.
Conclusion: The regression formulas obtained in this study can accurately (with a probability of 99%) predict refractive astigmatism, using corneal astigmatism.
 

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Background and Objectives: The color vision evaluation of gas station workers in Isfahan City.
Methods: This cross-sectional comparative study was performed on workers at gas stations in Isfahan; all the workers were men. The participants were divided into two 40-people groups of exposure and non-exposure (the members of the fuel sales department). The participants had better vision than 8/10 and no underlying problems or eye disease. Besides, examination, including color vision was performed for all subjects. Color vision was assessed using the D15 test under high to medium light conditions. Also, the color vision test was performed monocularly. Then, the obtained data were analyzed using SPSS V. 22.
Results: The two study groups significantly differed in terms of color vision impairment index (P <0.001). Also, more color vision defects were seen in the group exposed to gasoline. The color confusion index (as the indicator of color vision defects) were 1.485 and 1.129 in exposure and non-exposure to gasoline groups, respectively. Thus, color vision defects were significantly higher in the exposure to gasoline group, compared with the control group.
Conclusion: The results of this study showed a difference in color vision index between the two groups. Therefore, long-term exposure to organic solvents, such as gasoline in fuel stations may cause color vision loss.
 

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Background and Objectives: We aimed to investigate the variation of heterophoria during a day in students with a normal visual system.
Methods: This cross-sectional observational study was conducted on 15 students aged 19 to 22 years with 20/20 visual acuity and normal binocular vision. Heterophoria was measured with a prism bar and alternate cover test at near and far distances (40 cm and 6 m). The measurement was performed from 8 to 10 PM in one day with 2 hours intervals.
Results: The Mean±SD age of students was 21.6±0.87 years (63% women and 37% men). The mean deviation in far and near order was 1.93 and 3.75 prism diopter, respectively. The Greenhouse-Geisser test concluded no significant difference between the measurements of distant heterophoria during the day (F=1.362, df=3.066, P=0.267). However, the near-distance results were significant (F=15.17, df=7, P˂0.05). The paired t-test results showed that the highest amount of exophoria was observed near 4 PM, which was significantly different from the initial value, and the difference increases at the end of the day so that the mean difference of the initial near exophoria value from 4 to 10 PM reached from -1.254 to -3.508.
Conclusion: Changes in refractive error or high order aberration increase near work and decrease the illumination during a day can induce force on accommodation and vergence. So, at the end of the day, the exophoria increases. Thus, it is preferable to perform eye examinations at the end of the day to make more accurate decisions about the diagnosis and treatment of patients.
 

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