e jafarzadehpur

Astigmatism is a common refractive error and is common in patients requiring cataract surgery. Cataract surgery is usually accompanied by an intraocular lens (IOL) implantation. However, global sanctions in Iran and the high cost of toric IOLs sometimes lead to the application of spherical IOLs and hence residual astigmatism. Given the average age of the middle-aged Iranian population, the need to address the issue of astigmatism and cataracts is clear. To evaluate the visual acuity and refractive errors in cataract patients with regular astigmatism after spherical IOL placement and to evaluate the results of the calculation formulas for determining IOL power.

This cross-sectional study was performed on 100 eyes of 72 patients aged 50 to 75 years with regular astigmatism who underwent phacoemulsification surgery and simultaneous spherical IOL implantation at Farabi Eye Hospital in Tehran. Patients' visual acuity was performed by LogMAR chart and refractive examination using Topcon autokeratorefractor preoperatively and one month after surgery. The results of preoperative and postoperative examinations, according to the formula used and target refraction, were statistically analyzed using analysis of variance, paired t-test, and Pearson correlation in SPSS software.

The selection of “Plano” target refraction, improved patients' vision and refraction. The mean of Uncorrected Distance Visual Acuity before and after surgery showed a significant difference (p<0.001). The mean of Corrected Distance Visual Acuity and spherical refractive error before and after surgery did not show a statistically significant difference (p>0.05). The mean of refractive and corneal astigmatism, before and after surgery showed a significant difference (p<0.001).

The age of cataract patients with astigmatism can be an indicator for choosing the appropriate IOL formula. Cataracts cause astigmatism by altering the Crystalline lens, which can be reduced with surgery. With accurate refraction, the quality of patients' vision can be increased with spectacles before cataract surgery. The SRK / T formula, which has the highest frequency among the three formulas, has better visual and refraction results.

The anterior corneal curvature has important role in diagnosis and management of keratoconus. The purpose of the present study is to determine the repeatability of anterior curvature of 5 corneal rings (1-5 mm from the corneal center) in keratoconus patients obtained by the Orbscan and Eyesys instruments and to determine the level of agreement of curvature measurements between two instruments. In this prospective study, anterior curvatures of 5 corneal rings were measured using Orbscan and Eyesys in 48 right eyes of 48 keratoconic patients. The mean age of patients was 31.6±4.7 and the grades of keratoconus of patients according to the maximum keratometry were mild (≤50 D), moderate (50-55D) and severe (≥55D). Statistical analysis was performed using Intraclass Correlation Coefficient and Repeated measures ANOVA for repeatability of each device. Pearson’s correlation coefficient, paired t test and Bland-Altman plot were also used for comparison of two techniques. In this study, the ICC showed high repeatability for measurements of each devices (ICC Eyesys=0.99, ICC Orbscan≥0.95, p<0.0001) in all corneal rings. According to repeated measures ANOVA, there was no significant difference between the repeated measurements of each device in all corneal rings. The Pearson’s correlation analysis showed high correlation between the measurements of Orbscan and those of Eyesys (r≥0.84, p<0.0001) in all rings. According to the paired t test, there was a significant difference in curvature measurements of Eyesys and those of Orbscan in all corneal rings (p<0.001). Also, the Bland-Altman plots showed low agreement between curvature measurements of two devices in all corneal rings. The present study showed that the anterior curvature measurements obtained by each of Orbscan and Eyesys instruments were repeatable in all corneal rings. Anterior curvature measurements of 5corneal rings obtained by Eyesys were steeper than those obtained by Orbscan and the two devices could not be replaced for anterior corneal curvature measurement in keratoconic eyes.

To predict the spherical refractive error and astigmatism based on Snellen chart and OPD-scan III visual acuity in visually normal individuals. This study was performed on seventy five participants with an age range of 18 to 35 years. Visual acuity and refractive errors were evaluated using both subjective Snellen chart and OPD-scan III devices. The Pearson correlation test was used to evaluate the correlation between visual acuity and refractive errors. Moreover, to predict refraction based on the visual acuity, linear regression was performed. The results of the Pearson correlation test showed a significant negative correlation between visual acuity and refractive error in the myopic group (p<0.0001, r=-0.859 for subjective visual acuity, r=-0.788 for objective visual acuity). In addition, there was a significant positive correlation in the hyperopic group (p<0.0001, r= 0.882 for objective visual acuity). However, there was no significant correlation between subjective visual acuity and spherical refractive errors. Also, no significant correlation was found between astigmatism and visual acuity of the eye (p>0.05). Considering the high correlation between visual acuity and spherical refractive errors in myopic groups, refraction may be estimated based on the visual acuity of the eye. While in hyperopic group, there is no possibility to predict the refraction based on subjective visual acuity. Considering the poor correlation between visual acuity and astigmatism, astigmatism cannot be estimated based on the visual acuity of the eye.

Refractive errors (myopia، hyperopia and astigmatism) could lead to an impaired quality of life affect a large proportion of the population worldwide، irrespective of age، sex and ethnic group. Such refractive errors can be easily diagnosed، measured and corrected with spectacles or other refractive corrections to attain normal vision. Since there is paucity of information in school children in Iran we aimed to investigate the distribution pattern of refractive status and prevalence of refractive errors in school-age children in Shiraz

A random sampling strategy in geographically defined clusters was used to identify children aged 6-15 years in Shiraz between 2008-2209. We carried out a school survey and actual eye examinations، including visual acuity measurements، stereopsis examination، anterior segment and eyeball movements، fundus examinations، and cycloplegic retinoscopy with 1% cyclopentolate.

Of 3065 selected individuals، 2683 were participated in the study (response rate 86. 6%). According to cycloplegic refraction، 4. 85% (95% (Cl)، 3. 52 to 6. 16) of the primary and middle school students were myopic and 4. 64% (95% Cl، 3. 52 to 6. 19) were hyperopic. For high school students، these rates were 22. 19 and 11. 4% respectively. Myopia and hyperopia were shown to be correlated with age. Prevalence of anisometropia، amblyopia and strabismus were 2. 51%، 2. 31 (95%CI 1. 51-3. 11) and 1. 83% (95%CI 1. 15-2. 50).

Compared to other published reports، the rate of myopia in the school children of Shiraz seems relatively high