High prevalence of refractive errors in 7 year old children in Iran

Background: The latest WHO report indicates that refractive errors are the leading cause of visual impairment throughout the world. The aim of this study was to determine the prevalence of myopia, hyperopia, and astigmatism in 7 yr old children in Iran. Methods: In a cross-sectional study in 2013 with multistage cluster sampling, first graders were randomly selected from 8 cities in Iran. All children were tested by an optometrist for uncorrected and corrected vision, and non-cycloplegic and cycloplegic refraction. Refractive errors in this study were determined based on spherical equivalent (SE) cyloplegic refraction. Results: From 4614 selected children, 89.0 participated in the study, and 4072 were eligible. The prevalence rates of myopia, hyperopia and astigmatism were 3.04 (95 CI: 2.30-3.78), 6.20 (95 CI: 5.27-7.14), and 17.43 (95 CI: 15.39-19.46), respectively. Prevalence of myopia (P=0.925) and astigmatism (P=0.056) were not statistically significantly different between the two genders, but the odds of hyperopia were 1.11 (95 CI: 1.01-2.05) times higher in girls (P=0.011). The prevalence of with-the-rule astigmatism was 12.59, against-the-rule was 2.07, and oblique 2.65. Overall, 22.8 (95 CI: 19.7-24.9) of the schoolchildren in this study had at least one type of refractive error. Conclusion: One out of every 5 schoolchildren had some refractive error. Conducting multicenter studies throughout the Middle East can be very helpful in understanding the current distribution patterns and etiology of refractive errors compared to the previous decade. © 2016. Iranian Journal of Public Health. All Right Reserved

Objective and subjective assessing efficacy of a lubricating drop in eyes wearing silicone hydrogel contact lenses

Purpose: To investigate the effect of a lubricating drop on optical quality, tear film stability, and subjective symptoms in individuals wearing silicone hydrogel contact lens. Methods: In this one-day, prospective single-center clinical study, Pre-lens Tear Deformation Time (PL-TDT), Root-Mean-Square (RMS) of Low Order Aberrations (LOA) and High Order Aberrations (HOA), individual twelve Zernike coefficients, and subjective symptoms were assessed in 43 volunteers (mean age 19.58 ± 1.63, 86 eyes) at 6 h after inserting the contact lens and then at 60 min after instilling a lubricating drop (Comfort drops, Avizor, Madrid-Spain). Results: PL-TDT, LOA-RMS, and HOA-RMS values measured before drop instillation were not significantly different with those measured after drop. None of the Zernike coefficients were significantly different after instilling lubricating drop. Statistically significant decrement in both frequency and severity values in blurry vision, dryness, discomfort, burning, itching, foreign body sensation, excessive blinking, and lacrimation were seen after drop instillation (all P < 0.05). Conclusion: Our results showed that although the lubricating drop did not improve the tear film stability and optical quality in the silicone hydrogel contact lens wearers, subjects experienced a subjective improvement. © 2016 Iranian Society of Ophthalmology

Tear Deformation Time and optical quality in eyes wearing silicone hydrogel contact lenses

Purpose To evaluate tear film stability and optical aberrations in eyes wearing plano Lotrafilcon B contact lenses (CL). Methods Tear Deformation Time (TDT) and aberrometric parameters were assessed in 86 normal emmetropic eyes before and 6 h after wearing CL. Result A statistically significant decrease in TDT and increase in root mean square (RMS) values of higher order aberrations (HOA) were revealed 6 h after CL insertion (both P < 0.001). The low order aberrations (LOA) RMS values measured with CL were higher than those in naked eyes, but the difference was not statistically significant. None of individual Zernike polynomials showed any significant alteration. Conclusion Our findings indicated that the Lotrafilcon B contact lens affects HOA more than LOA. The tear film was less stable after wearing CL. © 2016 Iranian Society of Ophthalmolog

The profile of astigmatism in 6�12-year-old children in Iran

Purpose: To determine the prevalence of astigmatism and its determinants in schoolchildren aged 6�12 years. Methods: The students selected by stratified cluster random sampling in Shahroud, north of Iran. Optometric examination included uncorrected visual acuity, refraction with autorefractometer, manifest refraction with retinoscopy followed by subjective and cycloplegic refraction (after two drops of cyclopentolate 1 with 5 min interval were instilled in each eye). A cylinder power �0.75 diopter (D) in at least one eye was considered as astigmatism. The prevalence of astigmatism was reported based on a cylinder power higher than 0.50, 1.00, and 2.00 D in cycloplegic refraction, followed by power vector analysis. Results: After applying the inclusion criteria, the data of 5528 children were analyzed. The prevalence of astigmatism was 16.7 (95 CI: 15.6�17.7) in total, 16.6 (95 CI: 15.2�18.0) in boys and 16.8 (95 CI: 15.2�18.3) in girls (p = 0.920) and decreased from 21.5 in 6-year-old children to 13.7 in 10-year-olds, and then again increased to 18.3 in children aged 12 years. Moreover, 17.2 (95 CI: 16.0�18.3) of urban and 12.1 (95 CI: 10.0�14.1) of rural children had astigmatism (p &lt; 0.001). The prevalence of with-the-rule, against-the-rule, and oblique astigmatism was 14.2, 2.1, and 0.33, respectively. The mean cylinder power was �1.31, �0.46, and �0.44 D in children with spherical myopia, emmetropia, and hyperopia, respectively (p &lt; 0.001). Urban students had a higher J0 and boys had a higher J45. Conclusion: The prevalence of astigmatism in this study was lower than previous studies. Astigmatism prevalence was markedly higher in urban children. © 2020 Spanish General Council of Optometr

Enantiomorphism and rule similarity in the astigmatism axes of fellow eyes: A population-based study Enantiomorfismo y similitud de la regla en los ejes del astigmatismo en ojos contralaterales: estudio poblacional

Purpose: To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. Methods: This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health at the slit-lamp. Axis symmetry was based on two different patterns: direct (equal axes) and mirror (mirror image symmetry) or enantiomorphism. Bilateral astigmatism was classified as isorule if fellow eyes had the same orientation (e.g. both eyes were with-the-rule) and as anisorule if otherwise. Results: Of the total cases of bilateral astigmatism, 80 were isorule, and in the studied population, the prevalence of isorule and anisorule astigmatism was 14.89 and 3.53, respectively. The prevalence of isorule increased with age (p 0.288). Both symmetry patterns reduced with age (p < 0.001). Among cases of bilateral astigmatism, 15.5 and 19.8 had exact direct and mirror symmetry, respectively. Conclusion: Bilateral astigmatism is mainly isorule in the population and anisorule astigmatism is rare. The enantiomorphism is the most common pattern in the population of bilateral astigmatism. © 2018 Spanish General Council of Optometr

Repeatability of curvature measurements in central and paracentral corneal areas of keratoconus patients using Orbscan and Pentacam

Purpose: To determine the repeatability of curvature measurements in 5 corneal rings (1�5 mm from the corneal center) in keratoconus (KCN) patients using the Orbscan and Pentacam and to compare the values of these devices. Methods: Forty-eight patients with a definite diagnosis of KCN were included in the study. Patients with any corneal scar or active disease or a history of ocular surgery were excluded from the study. The right eye of the patients was studied three times with the Orbscan and Pentacam. The repeatability of the curvatures of 5 corneal rings (1�5 mm from the corneal center) was evaluated using the Orbscan and Pentacam, and the agreement of their values was analyzed. Results: The intraclass correlation coefficient (ICC) of three measurements was at least 0.94 (P < 0.0001) for the Orbscan and at least 0.88 (P < 0.0001) for the Pentacam in all corneal rings. According to the grade of KCN, the Orbscan had a low ICC in the 2 mm ring in grades 2 and 3 (ICC = 0.750 and 0.298, respectively). Repeated measures ANOVA showed no significant difference between the repeated measurements of the Orbscan and Pentacam in all corneal rings. The paired t-test showed a significant difference in curvature measurements in all rings except for the 5-mm ring between the two devices (P < 0.0001). The Bland-Altman plot showed a week agreement between these two devices in 1�4 mm corneal rings in curvatures more than 45 D. Conclusions: According to the results of this study, keratometry readings are highly repeatable in Pentacam and Orbscan devices in all corneal rings. Despite the high correlation between curvature measurements of the Orbscan and Pentacam, there was a significant statistical and clinical difference between the results of two devices in all corneal rings (except the 5-mm ring), and the curvature measurements of the Pentacam were steeper than Orbscan measurements. © 2018 Iranian Society of Ophthalmolog

Enantiomorphism and rule similarity in the astigmatism axes of fellow eyes: A population-based study Enantiomorfismo y similitud de la regla en los ejes del astigmatismo en ojos contralaterales: estudio poblacional

Purpose: To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. Methods: This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health at the slit-lamp. Axis symmetry was based on two different patterns: direct (equal axes) and mirror (mirror image symmetry) or enantiomorphism. Bilateral astigmatism was classified as isorule if fellow eyes had the same orientation (e.g. both eyes were with-the-rule) and as anisorule if otherwise. Results: Of the total cases of bilateral astigmatism, 80 were isorule, and in the studied population, the prevalence of isorule and anisorule astigmatism was 14.89 and 3.53, respectively. The prevalence of isorule increased with age (p 0.288). Both symmetry patterns reduced with age (p < 0.001). Among cases of bilateral astigmatism, 15.5 and 19.8 had exact direct and mirror symmetry, respectively. Conclusion: Bilateral astigmatism is mainly isorule in the population and anisorule astigmatism is rare. The enantiomorphism is the most common pattern in the population of bilateral astigmatism. © 2018 Spanish General Council of Optometr

Does astigmatism alter with cycloplegia?

Purpose To determine the effect of the cyclopentolate 1 on the cylindrical and spherical components of the refraction. Methods Three hundred seventy-five eyes of 195 subjects, including 74 males and 121 females, aged from 3 to 59 years were refracted before and 30 min after cyclopentolate 1 eye drop instillation. To compare cylindrical data, power vector analysis (J0 and J45 cross cylinder) was applied. Results A statistically significant difference between the J0 values of the noncycloplegic and cycloplegic refraction was revealed (P = 0.006) while the J45 values did not significantly differ. 95 limit of agreement for dry and cycloplegic values of the J0 and J45 were �0.22 to 0.25 and �0.19 to 0.20, respectively. Astigmatism difference was separately analyzed in emmetropic, myopic and hyperopic eyes. The J0 difference was significant (P = 0.014) only in hyperopic eyes. Spherical equivalent (SE) values in cycloplegic refraction were significantly more hyperopic than those yielded in dry refraction by mean difference of +1.16 ± 1.20 diopters (P &lt; 0.0001). Spherical equivalent difference (SED) values were negatively correlated with age. Conclusions Our findings indicated that cycloplegic drops caused a statistically significant shift in the �with the rule� and �against the rule� astigmatisms, although the oblique astigmatisms remained unaffected. Further research with larger sample sizes are needed to answer what mechanisms are involved in changing cylinder with cycloplegia. © 2016 Iranian Society of Ophthalmolog

The distribution of ocular biometry in Iranian school children

Purpose: To determine the distribution of axial length (AL), vitreous chamber depth (VCD), anterior chamber depth (ACD), lens thickness (LT), lens power (LP), radius of curvature (CR), and white-to-white corneal diameter (WTW) in the 14-20 year age range. Methods: In a cross-sectional study, sampling was done from Aligoodarz high schools using multistage simple cluster sampling. For all students, visual acuity and non-cycloplegic refraction tests were performed. Biometric components were measured using Allegro Biograph (WaveLight AG, Erlangen, Germany). Results: In this report, data from 434 cases was used in the analysis; of these 222 (51.2) were females. Mean and 95 confidence intervals of AL, VCD, ACD, LT, LP, CR, and WTW in the studied sample were 23.4 mm (23.32 to 23.48), 16.82 mm (16.74 to 16.9), 3.14 mm (3.12 to 3.16), 3.44 mm (3.42 to 3.46), 22.65 diopter (22.47 to 22.83), 7.74 mm (7.72 to 7.76), and 12.26 mm (12.22 to 12.3), respectively. In the multiple regression model, AL, VCD, ACD, CR, and WTW was significantly higher in boys while mean LT and LP were significantly higher in girls. The distributions of AL, ACD, LT, and CR were significantly different from normal. The distributions of AL, LT, and CR were leptokurtic, unlike ACD which had a platykurtic distribution pattern. Conclusion: In this report, we describe the normal ranges of ocular biometric components in a sample population of 14-20 year old Iranians. ACD in this study was shorter and WTW was larger than previous studies and other components were in the midrange. More studies throughout Iran are needed to verify a shorter ACD and larger WTW. All components of ocular biometry showed significant inter-gender differences. © 2014 by the Iranian Society of Ophthalmology

Enantiomorphism and rule similarity in the astigmatism axes of fellow eyes: A population-based study Enantiomorfismo y similitud de la regla en los ejes del astigmatismo en ojos contralaterales: estudio poblacional

Purpose: To evaluate the relationship patterns between astigmatism axes of fellow eyes (rule similarity and symmetry) and to determine the prevalence of each pattern in the studied population. Methods: This population-based study was conducted in 2015 in Iran. All participants had tests for visual acuity, objective refraction, subjective refraction (if cooperative), and assessment of eye health at the slit-lamp. Axis symmetry was based on two different patterns: direct (equal axes) and mirror (mirror image symmetry) or enantiomorphism. Bilateral astigmatism was classified as isorule if fellow eyes had the same orientation (e.g. both eyes were with-the-rule) and as anisorule if otherwise. Results: Of the total cases of bilateral astigmatism, 80 were isorule, and in the studied population, the prevalence of isorule and anisorule astigmatism was 14.89 and 3.53, respectively. The prevalence of isorule increased with age (p 0.288). Both symmetry patterns reduced with age (p < 0.001). Among cases of bilateral astigmatism, 15.5 and 19.8 had exact direct and mirror symmetry, respectively. Conclusion: Bilateral astigmatism is mainly isorule in the population and anisorule astigmatism is rare. The enantiomorphism is the most common pattern in the population of bilateral astigmatism. © 2018 Spanish General Council of Optometr