refractive errors

Blue-blocking lenses, including both spectacles and intraocular lenses, are designed to selectively reduce the intensity of short-wavelength visible light and UV radiation using a chromophore. Unlike standard spectacle lenses, which only offer varying degrees of UV protection, blue-blocking lenses provide additional benefits such as enhancing visual performance, reducing eye fatigue from digital screens, protecting the retina from phototoxicity, and minimizing disruption of the circadian rhythm caused by blue light-emitting devices used in the evening. Research has shown that the length of the eye tends to increase over time, especially during the first 10 months of life, indicating the importance of this period in eye development. The Purkinje shift is a phenomenon where the eye becomes more sensitive to blue light in the dark, and it is a normal physiological process. However, there is concern that prolonged use of blue-cut lenses in children may affect the development of eye length and contribute to an increase in refractive eye disorders.

To evaluate the patterns of refractive errors among patients who visited Ibn Al Haytham hospital, Baghdad, Iraq, from January 2023 to October 2023.

This cross-sectional observational study was conducted between January 2023 and December 2023. Participants aged 18 and above were selected using random sampling from individuals referred for eye care at the Ibn Al Haytham hospital, Baghdad, Iraq, during the study period. Data were collected using a standardized checklist. Visual acuity tests with a Snellen chart, and refractive error measurements using an autorefractometer were performed.

Of the 309 participants included in the study, myopia was the most prevalent condition, affecting 63.8 % (n = 197), while hyperopia was present in 36.2 % (n = 112). Additionally, 40.1 % (n = 124) of participants had astigmatism, and 34.63 % (n = 107) had abnormal visual acuity. The distribution of refractive errors by gender showed that myopia (68.02 %, P = 0.001) and astigmatism (69.35 %, P = 0.016) were more prevalent in female participants. Job status was also associated with the distribution of refractive errors (P = 0.040) and astigmatism (P = 0.002). Finally, family history showed a significant association with the pattern of refractive errors among participants (P = 0.035).

The study results highlight significant variations in the prevalence and patterns of refractive errors among patients at Ibn Al Haytham hospital, Baghdad, Iraq, with myopia being the most common condition. Gender, job type and familial history were found to have significant associations with different types of refractive errors.

The possible effects of refractive errors on vestibulo-ocular reflex (VOR) has been a conflicting issue. The aim of this study was to evaluate the effects of induced myopia on VOR using the ocular Vestibular Evoked Myogenic Potential (oVEMP).

In this cross-sectional quasi-experimental study, 35 emmetropic and normal subjects with the mean age of 23.89 ± 3.93 (range, 20–40 years) without any ocular, nervous system, and vestibular disorders, underwent the oVEMP test in the comprehensive rehabilitation center of Mashhad University of Medical Sciences. The oVEMP was performed under five different conditions of testing binocularly, monocularly, and when myopia was induced with the use of spherical lenses of +1.00, +3.00, and +5.00 diopters, respectively. There were 2 to 5 min of rest with closed eyes after each condition to avoid adaptation, fatigue, and any other sources of bias. Mean latencies of oVEMP waves (N1 and P1) and amplitudes of N1–P1 complex were measured.

There was no significant difference between the right and left sides (P > 0.05). The induced myopia significantly increased the N1 and P1 latencies using lenses of +1.00, +3.00, and +5.00 diopters but the amplitudes of N1–P1 complex were not influenced by the different amounts of induced myopia. There was no significant difference among the different conditions of induced myopia either (P > 0.05).

Induced myopia could affect the VOR due to prolonging the latencies of oVEMP waves. However, the amplitudes were not affected and the effects of multiple degrees of induced myopia were not significantly different.

 The problem of refractive errors is one of the most common issues in ophthalmology and the diagnosis and treatment of refractive errors in students is of great importance. Considering the importance of timely detection of refractive errors as an anomaly in students and also the lack of comprehensive information in this field and the lack of a similar study in the city of Kermanshah, it was done in 2019.

 In this cross-sectional study done in 2019. The subjects were selected by available sampling method. Using frequency tables, chi-square test in agreement tables, and Pearson correlation coefficient test was performed. For data analysis, SPSS 21 statistical software and a significant level of 0.05 were considered.

 Among 296 high school students in Farzanegan High School in Kermanshah, more than half had refractive errors in at least one case. Most refractive errors included myopia, which was associated with aging in this period. Also, the prevalence of stigmatism in this period was about 14%, which was reported more than in other studies. Also, most of the association with stigmatism was myopia in individuals. Also, no relationship was found between students' rates and refractive errors (P> 0.05).

 Due to the high prevalence of myopia associated with astigmatism, it seems that screening programs to identify, follow up and treat refractive errors in students in Kermanshah and the country, in general, is of particular importance and should be done regularly. And be scheduled.

 The study aims to determine the age- and sex-adjusted prevalence of refractive errors and its related factors among the adult population of southeastern Iran.

 The current study included 9280 individuals aged 35 to 70 years using a multistage random sample method from October 2015 to January 2019 as a part of a Persian cohort study in Zahedan. Uncorrected and corrected vision, objective noncycloplegic, and subjective refraction were measured, with all participants undergoing ophthalmoscopy, slit-lamp biomicroscopy, fundoscopy, refraction, and retinoscopy. Data were analyzed using SPSS version 23.0 statistic software and described as percentage, odds ratio, and 95% confidence interval. Comparisons between groups and relationships among risk factors and refractive errors were performed with chi-square, nominal, and multiple regression analysis.

 The prevalence of low and moderate myopia, high myopia, low and moderate hyperopia, high hyperopia, low and moderate astigmatism, and high astigmatism was 24.2 (95% CI: 22.40 - 25.90), 1.5(95% CI: 0.00 - 3.53), 16.1(95% CI: 14.20 - 17.90), 1.3(95% CI: 0.00 - 3.30), 35.6 (95% CI: 33.90 - 37.30), and 3.8 (95% CI: 1.80 - 5.70) percent, respectively. The prevalence of refractive errors significantly varied across different age groups overall and by sex (P = 0.01). The proportion of refractive errors also significantly differed by education (P = < 0.001). The prevalence of against the rule, with the rule, and oblique astigmatism was 32.8 % (95% CI: 31.10 - 34.20), 42.1% (40.50 - 43.60), and 24.9% (23.10 - 26.60), respectively. The risk of astigmatism was significantly lower in men than in women (OR = 0.75; 95 % CI: 0.60 - 0.90). Based on multiple regression, the risk of myopia (OR = 2.07; 95 % CI: 1.60 - 2.60) and hyperopia (OR = 25.38; 95 % CI: 18.70 - 34.3) was higher in the age group 65 to 75 years compared to the younger group.

 The present study provided valuable information on the prevalence of refractive errors in the adult population in south-eastern Iran. The findings underscore the need for comprehensive eye care services, particularly for older individuals and those with lower education levels. Further prospective research is warranted to explore the factors contributing to refractive errors and to develop effective strategies for its prevention and management.

The present study aimed to assess the effect of refractive error (RE) correction on stereopsis.

A total of 62 participants underwent comprehensive ophthalmic examinations, which included measurements of visual acuity, RE, stereopsis, ocular alignment, as well as examinations of the anterior and posterior ocular segments. Stereopsis was evaluated using the TNO random dot stereogram booklet at a distance of 33 cm, both with and without RE correction. The results were then compared to evaluate the impact of RE correction on stereopsis.

Our findings revealed that correcting one diopter of the spherical and spherical equivalent components of RE led to a significant improvement in stereopsis, with improvements of 30.884 and 30.373 seconds of arc, respectively (P = 0.001). However, the correction of other components of RE did not demonstrate a statistically significant effect on improving stereopsis. Additionally, we found no significant correlation between different types and severities of refractive errors and stereopsis.

Correcting the spherical and spherical equivalent components of refractive error may enhance stereopsis across various types of refractive errors.

There is an integration between visual and vestibular systems. Changes in visual inputs can result in different changes in the Vestibulo-Ocular Reflex (VOR). This review study investigate the changes in VOR due to changes in visual inputs. In this regard, the effects of different conditions such as visual deprivation, changes in visual acuity, visual-vestibular conflict, and binocular vision dysfunction on VOR were assessed.

Changes in visual inputs and visual-vestibular conflicts can lead to different changes in VOR.

The changes in VOR effects vary from slight to severe transformation dependent on the time course, severity and duration of changes in visual inputs.

To evaluate parental perspectives of accessing eye care for children aged under seven years.

The survey was conducted during September 2020 to March 2021 using online applications and distributed to parents whose children were between the ages of three and seven years. The survey included parents’ background, their knowledge of the provision of eyecare services, and the possible barriers that existed to access eye-care services. The relationship between parents’ knowledge, barrier scores, level of parental education, and demographic or socioeconomic status was assessed using nonparametric tests.

In total, 1037 questionnaires were completed. The respondents were from 50 cities across Saudi regions. The participants’ age was 39 ± 7.5 years, and 54% of them had at least one child under the age of seven (n = 564). Further, 47% had not taken their children for vision screening at reception/year one (n = 467). In addition, 65% of them were not aware of the mandatory screening program at reception/year 1; whereas, only 20% (n = 207) knew how to access eye-care services; and only 39% of the children had undergone any kind of eye or vision test. The pathways to eye care and the cost of eye services/glasses were the main limitations. The parents’ responses were significantly influenced by their demographic and socioeconomic characteristics (Kruskal Wallis, P < 0.05).

There was a need for enhancing parent information on how to access eye care for young children and the currently available vision screening programs. Finally, a national protocol to cover the cost of the eye exam as well as spectacle prescription shall be proposed as a mean of incentive.

Uncorrected refractive error is the leading cause of vision impairment in India. Myopia is a common refractive error that can also be defined by a spherical equivalent (SE) ≤−0.5 dioptre (D). To explore the combined effect of Yogic eye exercise and Diet compared with Yogic eye exercise in the management of myopia.

A comparative study with 28 students diagnosed with myopia was randomly assigned into two groups. Group A received a naturopathic diet protocol and Yoga eye exercises, and Group B received Yogic eye exercises. Improvement in myopia was assessed as the mean change in refractive error -Spherical equivalent (SE) from baseline.

The mean SE values were reduced post-intervention in both groups. Within-group comparison of SE pre- and post-intervention showed a significant reduction in SE measures in Yoga and diet (Group A) for the right and left eye at 95% CI with a p-value of 0.003 and 0.01 respectively. There were no significant changes in SE values in the Yoga-only group. When compared between groups, no statistically significant changes were observed in SE.  

The group that followed the diet combined with Yoga showed better improvement in pre-and post-assessments for both eyes. But when compared between the two groups there were no statistically significant changes in SE. Yogic eye exercise proved beneficial in both groups, but the results are better when combined with diet. The findings need to be verified further by conducting a large-scale placebo-controlled clinical trial with a wider population base on diverse age groups.

To estimate the prevalence, burden of refractive errors and their associated trend from 1990 to 2018 and geographic inequalities in Iran.

Data regarding the epidemiology of refractive errors was extracted from three different sources: systematic review of published literature, data from visual school screening programs, and data from Iran’s national health survey (NHS). The pool of all available data on refractive errors as well as demographic, location, and socioeconomic status covariates were fitted in spatio-temporal and Gaussian process regression models to predict the prevalence of refractive errors from the years 1990 to 2018 in 31 provinces grouped by age and sex in order to calculate years lived with disability (YLDs).

In 2018, the age-adjusted prevalence of refractive errors was 16.32% (95% uncertainty interval [UI]: 12.44–21.48%) in both sexes, 17.98% (95% UI: 13.74– 23.61%) in women, and 14.66% (95% UI: 11.14–19.36%) in men. The prevalence of refractive errors reveals that it increases with age. Refractive errors contributed to 441.41 and 348.38 YLDs in men and women, respectively. The age-standardized prevalence growth was 31.30% in females and 24.32% in males from the years 1990 to 2018. Significant geographical heterogeneity was observed. The agestandardized YLDs rates of refractive errors represent an increasing trend of 28.9% increase from 1990 to 2018.

Over 28 years, the prevalence of refractive errors increased significantly. Women tend to have higher rates of prevalence. The prevalence increased in older ages. Border provinces had the lowest prevalence. Agestandardized YLDs rates of refractive errors increased by about 30%.

To determine and compare ocular characteristics and refractive errors between thalassemia major patients and normal subjects.

In this study, 71 thalassemia major patients and 79 age and sex matched healthy subjects that were selected in an ongoing manner underwent complete optometric and ophthalmic examinations including auto refraction, subjective refraction, fluorescein tear break- up time, and pachymetry after anthropometric measurements.

The results showed that the mean UCVA was better in the control group versus the thalassemia group (p<0.001) while there was no difference in BCVA between the two groups (p=0.416). Moreover, the mean spherical equivalent was 0.38±0.13 D less in the thalassemia group compared to the control group (p=0.007) while corneal power (p<0.001) and cylinder power (p=0.001) were larger in thalassemia patients. Most common type of astigmatism was against the rule pattern in thalassemia patients and with the rule pattern in the control group (p<0.001). The mean tear break-up time was 11.35 ± 6.43 in the thalassemia group and 14.63 ± 5.79 in the control group (p=0.001), and the mean near point of accommodation (NPA) (p=0.009) and near point of convergence (NPC). (p=0.003) were significantly smaller in the thalassemia group compared to the control group.

These patients suffer from a myopic shift due to exaggerated responses to changes in ocular growth, dry eye secondary to goblet cell loss, and a higher prevalence of vertical astigmatism due to eyelid laxity and pressure on the cornea. Therefore, regular ophthalmological evaluations are highly recommended in these patients.

Visual skills play a pivotal role in athletic performance. However, in a professional setting, visual assessment is limited to a brief examination of visual acuity by the Snellen chart. This is while visual skills in sport comprise several other components.

This study aimed to evaluate the potential relationship between visual skills and sports injuries in professional soccer players.

Through a prospective cohort study between September 2017 and October 2018, professional soccer league players were recruited for a complete eye examination including visual acuity, field of vision, and color discrimination as pre-competition examination. Any possible relationship between an abnormal eye finding and sports injury during the upcoming season was investigated.

A total of 386 male soccer players in 4 different playing positions were recruited from 16 league teams. Myopia, visual field defects, and green/blue/red color blindness were the most common visual impairments. Overall, there was no significant relationship between abnormal visual skills and the incidence of low back and upper extremity injuries among soccer players. However, a logistic regression model showed that the odds of quadriceps injury is 1.92 times higher (P-value: 0.005) for one diopter increase in both eyes’ sum of refractive error. There is also an increased risk of concussion in players who have visual field defects (P-value < 0.005).

Visual field defects can put soccer players at a higher risk for concussion. Moreover, uncorrected refractive eye errors will increase the incidence of lower limb injuries, mostly quadriceps injuries.

To determine the distribution of keratometry values in a wide age range of 6-90 years.

In this cross-sectional study, samples were selected from two villages in Iran using multi-stage random cluster sampling. After completing optometry and ophthalmic examinations for all cases, corneal imaging was done using Pentacam, and keratometry values were determined.

Of the 3851 selected people, 3314 people participated in the study, and after applying the exclusion criteria, analyses were done on data from 2672 people. Mean age of the participants was 36.30 ± 18.51 years (from 6 to 90 years). Mean keratometry (mean‑K) in flat and steep meridians was 42.98 (42.9‑43.06) diopters (D) and 43.98 (43.91‑44.07) D, respectively. Average of mean‑K was 43.48 (43.41‑43.56) D. Mean‑K increased linearly up to the age of 70 years, and the cornea became slightly flat afterwards (coefficient = 0.01; P < 0.001). Mean‑K was significantly higher in females (P < 0.001). Myopic cases had the highest mean‑K (P < 0.001). The correlation of mean‑K with age, gender, central corneal thickness, anterior chamber depth, pupil diameter, and spherical equivalent was investigated in a multiple regression model. Only older age and female gender showed a statistically significant association with mean‑K. Overall, 31.62% (29.14‑34.09) of the sample in this study had at least 1.0 D of corneal astigmatism.

This is one of the few studies worldwide that demonstrates changes in keratometry in a wide age range from childhood to old age. Results indicated that age and gender are variables associated with keratometry

 To evaluate the stabilization time of astigmatism and refractive errors after cataract surgery using phacoemulsification and foldable lens implantation.

 The present cross-sectional study was carried out with convenience sampling method and included patients who underwent cataract surgery using phacoemulsification and implantation of foldable intraocular lens. The patients were evaluated and their data including age, sex, uncorrected visual acuity, best corrected visual acuity,  corneal cylinder, cylinder axis,  Sim K, and intra ocular pressure were recorded prior to the surgery as well as in days 2, 3, 4, weeks 1, 2, 5 and day 75 post surgery.

 Eighty one eyes of 77 patients with mean age of 61.39 ± 10.9 years were evaluated. The mean follow up time was 60.5 ± 48.86 days. The mean keratometry before surgery was 44.90 ± 1.85 diopters, while the mean axial length, the mean intraocular pressure and the mean astigmatism were 23.15 ± 1.98 mm, 14.01 ± 2.95 mmHg and 0.99 ± 1.10 diopters, respectively. The mean postoperative keratometry at last visit was 45.34 ± 1.80 diopters, and the mean intraocular pressure and astigmatism were, 12.46 ± 2.87 mmHg and 1.14 ± 0.96 diopters, respectively. The mean time for refraction stabilization was 11.46 ± 11.40 days and the mean stabilization time for astigmatism was 10.18 ± 11.34 days.

 In the present study the mean stabilization time for refraction and astigmatism after cataract surgery in an Iranian population using phacoemulsification and foldable lens implantation was comparable with previous studies.

According to global statistics, in every society, more than 10% of children are born with different characteristics from those of their peers, meaning they are mentally different from their peers. Children with intellectual disabilities are at a greater risk of refractive errors and other ocular problems. Regarding this, the present study was conducted to investigate the prevalence of refractive errors and ocular findings in children with intellectual disabilities studying at the special schools of Hamadan, Iran, within 2017-18.

This cross-sectional study was conducted on 90 students with intellectual disabilities studying at the exceptional schools of Hamadan in 2017-18. The data was collected using a checklist recording such data as demographic information, level of education, and eye examination results. Visual acuity, refraction, slit-lamp examination, and fundoscopy were performed by an optometrist and an ophthalmologist. Data analysis was performed in SPSS software (version 16.0; SPSS Inc., Chicago, IL) at a significance level of <0.05.

The mean age of the students was 9.4±2.7 years (age range: 6-18 years). Based on the data, 56 (62.2%) cases were female. With regard to the ocular findings, 78 (86.7%), 16 (17.8%), and 12 (13.3%) students had refractive errors, amblyopia, and strabismus, respectively. The most common refractive error in students was mixed astigmatism (n=66, 73.3%), followed by hypermetropia (n=35, 38.9%). Refractive errors and ocular diseases had a higher prevalence in female students under the age of 11 years and preschoolers; however, this difference was not statistically significant. Out of 78 children with refractive errors, 18 (23.1%) cases had an ocular disease (P=0.063).

According to the findings of this study, the prevalence of refractive errors and eye diseases was higher in children with an intellectual disability than in the general population. Furthermore, the girls and children with a younger age were found to be at a greater risk of ocular disorders. Consequently, the screening or periodic examination of these children is a measure of vital importance.