High prevalence of myopia in an adult population, Shahroud, Iran

Distribution and prevalence of refractive error in Iranian adult population results of the PERSIAN eye cohort study PECS

The Persian Eye Cohort Study, a population-based cross-sectional study from 2015 to 2020, examined refractive error prevalence among 48,618 Iranian adults aged 31 to 70. The study encompassed six centers in Iran, employing random cluster sampling for demographic, medical, and socioeconomic data collection through interviews. Ophthalmic exams included visual acuity, automated and manual objective refraction, subjective refraction, slit lamp, and fundus examinations. Using the spherical equivalent definition, the sample population was categorized into groups. Results indicated a mean age of 49.52 ± 9.31 and a mean refractive error of 0.26 diopters (D) ± 1.6 SD (95% CI - 0.27 to -0.24), ranging from -26.1 to + 18.5 SD. Prevalence of myopia (< -0.5D) and hyperopia (> + 0.5D) was 22.6% (95% CI 22.2-23%) and 12.5% (95% CI 12.1-12.8%), respectively. Regarding different age groups, the prevalence of hyperopia and astigmatism exhibited a steady and significant rise with increasing age (p-value < 0.001 for both). The prevalence of Myopia, however, showed a distinctive pattern, initially increasing in adults under 45, declining in those aged 55-64, and rising again among individuals aged 60 and older. Female gender, older age, urban residency, higher education, higher income, and Fars ethnicity were significantly related to a higher prevalence of myopia (p-value < 0.001 for all). Female gender (p-value < 0.001), aging (p-value < 0.001), urban residency (p-value = 0.029), and lower-income (p-value = 0.005) were significantly related to higher prevalence of hyperopia. Astigmatism (> 1D) was prevalent in 25.5% of participants (95% CI 25.1-25.9%) and correlated with male gender, aging, urban residency, illiteracy, and higher income (p-value < 0.001, < 0.001, < 0.001, < 0.001, 0.014, respectively). The study's comparison with regional and international surveys highlighted the increase in myopia among those over 65 due to higher nuclear cataract rates in older adults. Myopia positively related to education, income, and urban residency, while hyperopia did not exhibit such associations.

Development of a web-based patient decision aid for myopia laser correction method

BACKGROUND

In the context of healthcare centered on the patient, Patient Decision Aids (PtDAs) acts as an essential instrument, promoting shared decision-making (SDM). Considering the prevalent occurrence of myopia, the objective of this study is to furnish exhaustive and easily comprehensible information to assist patients in making well-informed decisions about their options for myopia laser correction.

METHOD

The research team developed a decision guide for myopia patients considering laser correction, aiming to facilitate informed decisions. The study followed the first four stages of the IPDAS process model: "scope/scoping," "design," "prototype development," and "alpha testing." Ten semi-structured interviews with patients (n = 6) and corneal specialist ophthalmologists (n = 4) were conducted to understand the challenges in selecting a laser correction method. Online meetings with 4 corneal specialists were held to discuss challenging cases. A comparison table of harms and benefits was created. The initial prototype was developed and uploaded on the internet portal. User feedback on software and text aspects was incorporated into the final web software, which was reviewed by a health education expert for user-friendliness and effectiveness.

RESULT

Educational needs assessment revealed concerns such as pain, daily life activities, return to work, the potential need for glasses ('number return'), eye prescription stability, and possible complications. These shaped the decision aid tool's content. Expert consensus was achieved in several areas, with some items added or extended. In areas lacking consensus, comments were added for clarity. Five clients assessed the web app (PDAIN), rating it 46/50 in user-centricity, 47/50 in usability, and 45/50 in accuracy and reliability, totaling 138/150. Post-piloting, software errors were documented and rectified. During the trial phase, five myopic users interacted with the software, leading to modifications. User feedback indicated the tool effectively enhanced understanding and influenced decision-making.

CONCLUSION

PDAIN, serves as a facilitative tool in the process of selecting a corneal laser correction method for myopic patients. It enabling Nearsighted patients to make informed decisions.

Myopia intervention and ultraviolet radiation related eye diseases: A narrative literature review

There has been an increased understanding of the protective effect of two or more hours in high lux light on the development and progression of myopia. The aim of myopia management is to reduce the incidence of high myopia and sight-threatening myopic complications. Equally important are the sight-threatening complications of ultraviolet radiation (UVR) on the eye and adnexal structures. This review will analyze the literature for both these epidemics to help guide public health policy. Whilst increasing childhood high lux light exposure is important, consideration of a holistic eye health policy should ensure that UV eye diseases are also prevented. The advent of ultraviolet (UV) fluorescence photography has increased our understanding that significant UV eye damage occurs in childhood, with 81% of children aged 12-15 years having signs of UV eye damage. Hence, the need to reduce myopia and protect from UV-related eye diseases needs simultaneous consideration. Advocating for eye protection is important, particularly as the natural squint reflex is disabled with dark sunglasses lenses. The pathways UV reaches the eye need to be considered and addressed to ensure that sunglasses offer optimum UV eye protection. The design of protective sunglasses that simultaneously allow high lux light exposure and protect from UVR is critical in combating both these epidemics.

PERSIAN Eye Cohort Study (PECS): Design, Methodology

BACKGROUND

To report the study protocol, methodology and latest enrollment data of a large epidemiological multi-central eye cohort named PERSIAN Eye Cohort Study (PECS), originating from the ongoing PERSIAN Cohort Study, to investigate the distribution of ophthalmic disorders in different regions and ethnicities of Iran, and determine their associations with various exposures of ophthalmic and non-ophthalmic nature.

METHODS

A central committee designed the study and equipped six chosen centers (Khameneh, Some'e Sara, Hoveizeh, Yazd, Rafsanjan and Zahedan). A focal point in each center conducted the study under close supervision of the central committee.

RESULTS

This ongoing study was launched in 2014. Out of 65,580 eligible participants of the PERSIAN Cohort, 48,618 individuals aged 35-70 have been enrolled in the PECS (response rate: 74.13%) until June 2021. Slit lamp and fundus photography were performed for 28,702 (59.03%) and 27,437 (56.43%) individuals, respectively.

CONCLUSION

This large epidemiological multi-central eye cohort can improve our epidemiological knowledge of the prevalent ophthalmic disorders in different regions and ethnicities of Iran, and determine their associations with various exposures of ophthalmic and non-ophthalmic nature. This will be very useful for future planned nationwide and global interventions.

High prevalence of refractive errors in an elderly population; a public health issue

PURPOSE

To determine the prevalence of myopia and hyperopia and their associated demographic and ocular factors in people 60 years of age and above.

METHODS

The sampling was performed using a multi-stage stratified random cluster sampling method. The complete demographic and case history information were collected through an interview. Then, all participants underwent optometric examinations including measurement of uncorrected and best-corrected visual acuity, objective, and subjective refraction. Myopia and hyperopia were defined as a spherical equivalent (SE) refraction worse than -0.50 diopters (D) and + 0.50 D, respectively.

RESULTS

Three thousand three hundred ten of 3791 invitees participated, and the data of 3263 individuals were analyzed for this report. The mean age of participants was 68.25 ± 6.53 (60 to 97) years, and 1895 (58.1%) of them were female (number of male/female participants = 1368/1895). The prevalence of myopia and hyperopia was 31.65% (95% CI: 29.68 -33.61) and 45.36% (95% CI: 43.36 -47.37), respectively. The prevalence of severe myopia and hyperopia was 1.14% (95% CI: 0.73 -1.55) and 2.27% (95% CI: 1.57 -2.97), respectively. Based on the results of multiple logistic regression, the prevalence of myopia had a statistically significant direct relationship with age (OR: 1.04; p < 0.001), history of glaucoma surgery (OR:2.75; p < 0.001), pseudophakia (OR: 2.27; p < 0.001), axial length (OR:3.05; p < 0.001), and mean keratometry (OR:1.61; p < 0.001). The education level was significantly inversely related to the myopia prevalence. Moreover, a history of glaucoma surgery (OR:0.44; p < 0.001), pseudophakia (OR = 0.15; p < 0.001), axial length (OR:35; p < 0.001) and mean keratometry (OR:0.62; p < 0.001) were significantly inversely related to the prevalence of hyperopia. 19% and 40.02% of myopic and hyperopic patients had complete visual acuity after correction of refractive error, respectively.

CONCLUSION

The prevalence of refractive errors was high in the Iranian elderly population. A large percentage of the elderly still did not have complete visual acuity after the correction of refractive errors indicating the necessity for attention to other ocular diseases in this age group. The history of cataract and glaucoma surgery could be associated with a myopic shift of refractive error.

Prevalence and risk factors of refractive error in Qinghai, China: a cross-sectional study in Han and Tibetan adults in Xining and surrounding areas

Background

Our study aimed to explore the prevalence and risk factors of refractive error (RE) in Han and Tibetan population aged 50–79 years in Xining and surrounding areas in Qinghai Province on Qinghai-Tibet Plateau.

Methods

As part of the China National Health Survey, our cross-sectional study compared the age-adjusted prevalence of RE in Han and Tibetan older adults aged 50–79 years in Xining and surrounding areas. A multivariate logistic regression model was used to identify risk factors for myopia and hyperopia.

Results

Among 769 Han participants and 476 Tibetan participants, the age-adjusted prevalence of myopia (spherical equivalent (SE) < − 0.5D), hyperopia (SE > + 0.5D), high myopia (SE < -6.0D) and astigmatism (cylindrical equivalent > = 0.5D) is 28.56, 22.82, 2.80, and 69.38%. Han participants have higher age-adjusted prevalence of myopia (32.93% vs 21.64%, p < 0.001), high myopia (3.93% vs 1.02%, p = 0.001) and astigmatism (72.14% vs 64.94%, p = 0.021) compared to Tibetan participants. Being Tibetan is the protective factor of myopia compared to being Han (OR 0.58, 95%CI 0.42–0.79, p < 0.001). Older age (p = 0.032), longer time length in rural area (p = 0.048), undergraduate/graduate education level (p = 0.031), lighter active level (p = 0.007) and lower BMI (p = 0.015) are risk factors for myopia. Older age (all p < 0.001) and pterygium status of the same eye (p = 0.013) also increase the hyperopia risk.

Conclusions

Our study found an overall prevalence of myopia of 28.56% in Xining and surrounding areas in adults older than 50 years. Han population has higher myopia risk than Tibetan population. More medical and social resources should be allocated to improve the vision and life quality of older adults.

IMI Impact of Myopia

The global burden of myopia is growing. Myopia affected nearly 30% of the world population in 2020 and this number is expected to rise to 50% by 2050. This review aims to analyze the impact of myopia on individuals and society; summarizing the evidence for recent research on the prevalence of myopia and high myopia, lifetime pathological manifestations of myopia, direct health expenditure, and indirect costs such as lost productivity and reduced quality of life (QOL). The principal trends are a rising prevalence of myopia and high myopia, with a disproportionately greater increase in the prevalence of high myopia. This forecasts a future increase in vision loss due to uncorrected myopia as well as high myopia-related complications such as myopic macular degeneration. QOL is affected for those with uncorrected myopia, high myopia, or complications of high myopia. Overall the current global cost estimates related to direct health expenditure and lost productivity are in the billions. Health expenditure is greater in adults, reflecting the added costs due to myopia-related complications. Unless the current trajectory for the rising prevalence of myopia and high myopia change, the costs will continue to grow. The past few decades have seen the emergence of several novel approaches to prevent and slow myopia. Further work is needed to understand the life-long impact of myopia on an individual and the cost-effectiveness of the various novel approaches in reducing the burden.

The prevalence of refractive errors in the Middle East: a systematic review and meta-analysis

PURPOSE

The purpose of the present study was to evaluate the prevalence of refractive errors in the Middle East region.

METHODS

In this meta-analysis, a structured strategy was applied to search databases PubMed, Web of Science, Scopus, and Google Scholar, databases as well as the reference lists of the selected articles to identify cross-sectional studies assessing the prevalence of refractive errors in the Middle East region until September 2019. The outcome measure was the prevalence of refractive errors, including myopia, hyperopia, and astigmatism, in two age groups of ≤ 15 years and > 15 years. The study results were combined using a random effects model at a confidence level of 95%.

RESULTS

The prevalence of myopia, hyperopia, and astigmatism was 4% (95% CI 4, 5), 8% (95% CI 6, 10), and 15% (95% CI 10, 19) in people less than or equal to 15 years and 30% (95% CI 25, 34), 21% (95% CI 15, 28), and 24% (95% CI 16, 31) in subjects over 15 years, respectively. The prevalence of myopia, hyperopia, and astigmatism was 3.5%, 12.4%, and 9.0% in male and 4.2%, 13.1%, and 9.9% in female subjects aged ≤ 15 years, respectively. In subjects aged > 15 years, the prevalence was 31.7%, 14.5%, and 31.5% in males and 31.9%, 11.2%, and 31% in females, respectively.

CONCLUSION

The prevalence of hyperopia is relatively high in Middle Eastern children, while the prevalence of myopia is higher in adults in this region. It seems that astigmatism is not a serious refractive problem in this region compared to the rest of the world.

Prevalence and risk factors of refractive error: a cross-sectional Study in Han and Yi adults in Yunnan, China

Background

Few studies have investigated the prevalence of refractive error (RE) in older adults in China, and most have focused on East China. Our study determined the prevalence and risk factors of RE in Han and Yi adults aged 40–80 years in rural and urban areas in Yunnan Province, Southwest China.

Methods

Our cross-sectional study is part of the China National Health Survey (CNHS). The age-adjusted prevalence rates of RE in Han and Yi adults aged 40–80 years in Yunnan were compared. We used a multivariate logistic regression model to identify risk factors for myopia and hyperopia.

Results

Among 1626 participants, the age-adjusted prevalence rates of myopia, hyperopia, high myopia and astigmatism were 26.35% (95%CI 24.01–28.70%), 19.89% (95%CI 18.16–21.61%), 2.64% (95%CI 1.75–3.53%), and 56.82% (95%CI 54.31–59.34%). Compared to the Yi population, the Han population had higher prevalence of myopia (31.50% vs 16.80%, p < 0.0001), high myopia (3.34% vs 1.31%, p = 0.049) and astigmatism (60.07% vs 50.67%, p = 0.026) but lower prevalence of hyperopia (16.58% vs 27.37%, p < 0.0001). In the multivariate logistic regression, individuals aged 45–49 (p < 0.001), 50–54 (p < 0.001), 55–59 (p = 0.014), and 60–64 years (p = 0.005) had a lower myopia risk than those aged 40–44 years, and individuals aged 50–54 (p = 0.002), 55–59, 60–64 and 65 years and older (all p < 0.001) had a higher hyperopia risk than those aged 40–44 years. Myopia was also associated with height (p = 0.035), time spent in rural areas (p = 0.014), undergraduate/graduate education level (p = 0.001, compared with primary school or lower education level) and diabetes (p = 0.008). The Yi population had a higher risk of hyperopia than the Han population (p = 0.025). Moreover, hyperopia was related to time spent in rural areas (p < 0.001) and pterygium (p = 0.019).

Conclusions

Our study investigated the overall prevalence of RE in older adults in rural and urban areas of Southwest China. Compared to the Yi population, the Han population had a higher prevalence of myopia, high myopia and astigmatism but a lower risk of hyperopia. The prevalence of myopia in the Han population in underdeveloped Southwest China was similar to that of residents in East China or of Chinese Singaporeans under urban or rural settings.

How to improve Iranians' vision health: on the national policy of preventing Iranians' blindness

AIM

To review vision health situation of Iranian community, analyze its determinants, and discuss the adopted improvement strategies by the Iran Ministry of Health and Medical Education (MOHME).

METHODS

This was a rapid situation analysis with a qualitative approach in three parts of recognition, orientation and implementation. The data were gathered via review of upstream documents, national and international experiences, and experts and stakeholders' opinions.

RESULTS

Eradicating trachoma, increasing human resources, increasing educational and research centers and promotion of ophthalmic technologies were important achievements in the field of vision health in Iran. Through these achievements, it seemed that the pattern of causes of blindness and low vision was similar to that of the developed countries. However, the review of Iranians' vision health indicators showed that a considerable percent of the blindness and low vision was avoidable through a national program demanding 3 types of interventions in social determinants of health (SDH), community education, and increasing the access to health care services by integrating the necessary services in primary health care system.

CONCLUSION

Managing the issue requires attentions from a national committee for preventing blindness with participation of all stakeholders, implementing a national survey on vision health, preparation of the primary level health centers including employment and education of community health workers (Behvarzes), optometrists and general practitioners, fair distribution of specialized human resources and establishing at least one specialized center in each province for referring patients from the primary levels.

The effect of transient glare on shape discrimination threshold in myopic adults

BACKGROUND

The aim was to evaluate the effect of transient glare on shape discrimination threshold (SDT) in myopic adults.

METHODS

A total of 162 myopic subjects were enrolled. Of these, 121 had low to mid myopia (-1.00 D to -6.00 D) and 41 had high myopia (-6.13 D to -10.25 D). All subjects had corrected visual acuity of 6/6 or better, and only data for the right eye were included in the study. SDTs were measured with circular D4 (fourth derivative of Gaussian) radial frequency patterns with a radial frequency of four, peak spatial frequency of three cpds, and mean radius of 1.5 degrees. SDTs were measured under two conditions, with and without the presence of transient glare while the stimulus was displayed (duration = 500 ms).

RESULTS

Without transient glare, SDTs were not different between the low-mid (23.84 ± 6.02 arcsec) and high myopia groups (25.17 ± 5.98 arcsec, p = 0.16, Mann-Whitney test). With transient glare, SDTs in all subjects became significantly higher (p < 0.001, Wilcoxon signed-rank test). SDTs in the high myopia group (55.53 ± 18.59 arcsec) became significantly higher than those in the low to mid myopia group (47.55 ± 15.06 arcsec, p = 0.014, Mann-Whitney test). The increments were significantly higher in the high myopia group (28.94 arcsec versus 20.88 arcsec, p = 0.031, Mann-Whitney test). Multiple regression showed that SDTs with glare were significantly associated with SDTs without glare (p < 0.001) and the presence of high myopia (p = 0.015).

CONCLUSIONS

Transient glare significantly increased SDTs in all myopic subjects, with the increment in subjects with high myopia being significantly larger than those in subjects with low to mid myopia.

Global and regional estimates of prevalence of refractive errors: Systematic review and meta-analysis

Purpose

The aim of the study was a systematic review of refractive errors across the world according to the WHO regions.

Methods

To extract articles on the prevalence of refractive errors for this meta-analysis, international databases were searched from 1990 to 2016. The results of the retrieved studies were merged using a random effect model and reported as estimated pool prevalence (EPP) with 95% confidence interval (CI).

Results

In children, the EPP of myopia, hyperopia, and astigmatism was 11.7% (95% CI: 10.5–13.0), 4.6% (95% CI: 3.9–5.2), and 14.9% (95% CI: 12.7–17.1), respectively. The EPP of myopia ranged from 4.9% (95% CI: 1.6–8.1) in South–East Asia to 18.2% (95% CI: 10.9–25.5) in the Western Pacific region, the EPP of hyperopia ranged from 2.2% (95% CI: 1.2–3.3) in South-East Asia to 14.3% (95% CI: 13.4–15.2) in the Americas, and the EPP of astigmatism ranged from 9.8% in South-East Asia to 27.2% in the Americas. In adults, the EPP of myopia, hyperopia, and astigmatism was 26.5% (95% CI: 23.4–29.6), 30.9% (95% CI: 26.2–35.6), and 40.4% (95% CI: 34.3–46.6), respectively. The EPP of myopia ranged from 16.2% (95% CI: 15.6–16.8) in the Americas to 32.9% (95% CI: 25.1–40.7) in South-East Asia, the EPP of hyperopia ranged from 23.1% (95% CI: 6.1%–40.2%) in Europe to 38.6% (95% CI: 22.4–54.8) in Africa and 37.2% (95% CI: 25.3–49) in the Americas, and the EPP of astigmatism ranged from 11.4% (95% CI: 2.1–20.7) in Africa to 45.6% (95% CI: 44.1–47.1) in the Americas and 44.8% (95% CI: 36.6–53.1) in South-East Asia. The results of meta-regression showed that the prevalence of myopia increased from 1993 (10.4%) to 2016 (34.2%) (P = 0.097).

Conclusion

This report showed that astigmatism was the most common refractive errors in children and adults followed by hyperopia and myopia. The highest prevalence of myopia and astigmatism was seen in South-East Asian adults. The highest prevalence of hyperopia in children and adults was seen in the Americas.

The prevalence of refractive errors among adult rural populations in Iran

PURPOSE

The aim was to determine the prevalence of myopia and hyperopia and related factors in underserved rural areas in Iran.

METHODS

Under random cluster sampling, two rural regions were randomly selected in the north and southwest of the country, and 3,061 persons over 15 years of age were invited into the study. After selecting samples, all participants had refraction, measurement of uncorrected vision and visual acuity and ocular health examination by slitlamp biomicroscopy.

RESULTS

Of the 3,061 invitees, 2,575 participated in the study (response rate: 84.1 per cent). After excluding those who met the exclusion criteria or had missing refractive data, eventually there were 2,518 subjects available for this analysis. The mean age of the participants was 44.3 ± 17.5 years (range: 16 to 93 years) and 1,460 of them (58.0 per cent) were female. The overall prevalence of myopia and hyperopia in this study was 25.2 per cent (95 per cent CI: 23.2 to 27.2) and 22.5 per cent (95 per cent CI: 20.6 to 24.4), respectively. The prevalence of myopia increased from 20.9 per cent in participants 16 to 20 years to 32.9 per cent in the 21 to 30 years age group, declined up to the age of 60 years and increased again afterwards. The lowest prevalence was 6.8 per cent observed in the 16 to 20 years age group and the highest was 45.8 per cent in 61- to 70-year-olds. In the final logistic regression model, myopia significantly associated with age, higher education levels and cataracts, while hyperopia associated with age, lower education levels and male gender.

CONCLUSION

In our study, the prevalence of myopia was lower and the prevalence of hyperopia was higher compared to most previous studies. The findings of this study imply that refractive errors vary by age.

The prevalence of refractive errors in 5-15 year-old population of two underserved rural areas of Iran

Purpose

To determine the prevalence of hyperopia and myopia and their associations with age and gender in 5- to 15-year-old children in underserved rural areas in Iran.

Methods

In this cross-sectional study, sampling was done using a multistage cluster sampling method from two underprivileged rural regions in Iran, and 3851 persons over 1 year old of age were invited to the study. After inviting the selected participants, examinations were conducted at a designated site in the selected villages. All participants underwent measurements of uncorrected and corrected visual acuity, manifest refraction, and a slit-lamp examination. Cycloplegic refraction was done by instilling cyclopentolate 1% eye drops in under 15-year-old participants.

Results

Of the 3851 selected persons, 3314 subjects participated (86.5%), and of these, 602 were in the 5–15 year age group. The prevalence of myopia and hyperopia in the studied children was 2.60% [95% confidence interval (CI): 1.10–4.10] and 4.00% (95% CI: 1.84–6.15), respectively. The prevalence of myopia in male and female children was 2.65% and 2.55%, respectively (P = 0.951). The prevalence of hyperopia in male and female children was 2.83% and 5.25%, respectively (P = 0.130). The prevalence of myopia in the villages of southwest and north was 2.42% and 3.09%, respectively (P = 0.618), and the prevalence of hyperopia was 4.71% and 2.10%, respectively (P = 0.0056).

Conclusion

The present report is a brief description of the status of refractive errors in children residing in underprivileged villages of two rural districts in Iran. As presented, the prevalence of myopia is not high, although the prevalence of hyperopia is in the mid-range compared to previous studies.

Higher order aberrations in a normal adult population

PURPOSE

To determine the distribution of Zernike coefficients and higher order aberrations in a normal population and its relationship with age, gender, biometric components, and spherical equivalent.

METHODS

During the first phase of the Shahroud cohort study, 6311 people of the 40-64-year-old population of Shahroud city were selected through random cluster sampling. A subsample of participants was examined with Zywave aberrometer (The Bausch & Lomb, Rochester, NY) to measure aberrations. Measurements of aberrations were done before cycloplegic refraction, and values generated from a minimum pupil diameter of 5 mm were reported in this analysis.

RESULTS

After applying exclusion criteria, 904 eyes of 577 people were analyzed in this study and mean age in this study was 49.5 ± 5.7 years and 62.9% were female. Mean root-mean-square (RMS) of the third-, fourth-, and fifth-order aberrations was 0.194 μm (95%CI: 0.183 to 0.204), 0.115 μm (95%CI: 0.109 to 0.121), and 0.041 μm (95%CI: 0.039 to 0.043), respectively. Total RMS coma (Z3 (-1,) Z3 (1), Z5 (-1), Z5 (1)), Total RMS trefoil (Z3 (-3,) Z3 (3), Z5 (-3), Z5 (3)), and spherical aberration (Z4 (0)) in the studied population was 0.137 μm (95% CI:0.129-0.145), 0.132 μm (95% CI: 0.123-0.140), and -0.161 μm (95%CI:-0.174 to -0.147), respectively. Mean higher-order Zernike RMS in this study was 0.306 (95% CI: 0.295-0.318) micrometer, and in the multiple model, it significantly correlated with older age and short axial length. The highest amounts of higher-order RMS were observed in hyperopes, and the smallest in emmetropes. Increased nuclear opacity was associated with a significant increase in HO RMS (p < 0.001). Analysis of Zernike coefficients demonstrated that spherical aberration (Z4 (0)) significantly correlated with nuclear cataract only (age-adjusted Coef = 0.37 and p = 0.012).

CONCLUSION

This report is the first to describe the distribution of higher-order aberrations in an Iranian population. Higher-order aberrations in this study were on average higher that those reported in previous studies.

The age-specific prevalence of myopia in Asia: a meta-analysis

PURPOSE

To estimate the age-specific prevalence of myopia in Asia.

METHODS

We searched PubMed, Embase, and Web of Science from their inception through September 2013 for population-based surveys reporting the prevalence of myopia in adults or children in Asia. We pooled the prevalence estimates for myopia by age groups and by year of birth using a random-effects model.

RESULTS

We identified 50 eligible population-based studies including 215,672 subjects aged 0 to 96 years reporting the prevalence of myopia from 16 Asian countries or regions. Myopia was found to be most prevalent (96.5%; 95% confidence interval, 96.3 to 96.8) in Koreans aged 19 years. There was no significant linear age group effect on the prevalence of myopia in the whole Asian population but there was a U-shaped relationship between both age and year of birth and the prevalence of myopia. The prevalence of myopia was also higher in those older than 70 years (36.3%; 95% confidence interval, 27.6 to 45.0) compared with other age groups, which revealed nuclear cataract-myopia shifts in refraction.

CONCLUSIONS

There is a large variation in the age-specific prevalence of myopia in Asia. A U-shaped relationship between age and the prevalence of myopia was found in the whole Asian population. The analysis is essential to guide future eye health care, intervention, and clinical management in Asia.

Spectral-domain optical coherence tomography of macula in myopia

The aim of this study is to determine the associations between regional macular thickness and gender, age, axial length, and degree of myopia in young and middle-aged healthy myopic eyes. One hundred and seventy-one subjects with -0.5 diopters of myopia or worse underwent prospective macular thickness measurement by Spectralis spectral-domain optical coherence tomography. Subjects' mean age was 32.40 ± 8.25 years (range 18 to 49 years), with 45 % being male. The mean degree of myopia was -4.57 ± 3.52 diopters, with a mean axial length of 25.09 ± 1.67 mm. Multivariate regression analysis demonstrated significantly thicker central (mean 9.13 µm thicker) and inner subfields (mean 8.55 µm thicker) in males (P values were <0.001 and 0.002, respectively). In addition, in both genders, for each millimeter of increased axial length, the central subfield thickness increased by 2.11 µm, the inner subfield decreased by 2.25 µm, and the outer subfield decreased by 3.62 µm (P values were 0.010, <0.001, and <0.001, respectively). Factors including gender and axial length affect baseline regional macular thickness in young and middle-age myopic subjects. The central subfield and inner subfield were affected by both gender and axial length, while the outer subfield was affected only by axial length. The macular thickness of myopic subjects with macular disease should be interpreted in light of these factors.

Epidemiology of myopia

Myopia is one of the most prevalent disorders of the eye. Higher myopia is associated with comorbidities that increase risks of severe and irreversible loss of vision, such as retinal detachment, subretinal neovascularization, dense cataract, and glaucoma. In recent years, reports from population-based prevalence studies carried out in various geographical areas now give a clear picture of the current distribution of refractive error. The scarcity of data from well-designed longitudinal cohort studies is still yet to be addressed. These studies have confirmed the previous data indicating that prevalence of refractive error varies according to ethnicity and geographic regions, and also point to an increase in myopia prevalence over the past half-century. The problem is particularly pronounced in affluent, industrialised areas of East Asia. Environmental risk factors for myopia related to socioeconomic status and lifestyle have been identified. The past decade has seen a greater understanding of the molecular biological mechanisms that determine refractive error, giving further support to the belief that myopia is the result of a complex interaction between genetic predisposition and environmental exposures. This review summarizes data on the prevalence, incidence, progression, associations, risk factors, and impact from recent epidemiological studies on myopia.

High prevalence of refractive errors in a rural population: 'Nooravaran Salamat' Mobile Eye Clinic experience

BACKGROUND

The prevalence of myopia and hyperopia and determinants were determined in a rural population of Iran.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

Using random cluster sampling, 13 of the 83 villages of Khaf County in the north east of Iran were selected. Data from 2001 people over the age of 15 years were analysed.

METHODS

Visual acuity measurement, non-cycloplegic refraction and eye examinations were done at the Mobile Eye Clinic.

MAIN OUTCOME MEASURES

The prevalence of myopia and hyperopia based on spherical equivalent worse than -0.5 dioptre and +0.5 dioptre, respectively.

RESULTS

The prevalence of myopia, hyperopia and anisometropia in the total study sample was 28% (95% confidence interval: 25.9-30.2), 19.2% (95% confidence interval: 17.3-21.1), and 11.5% (95% confidence interval: 10.0-13.1), respectively. In the over 40 population, the prevalence of myopia and hyperopia was 32.5% (95% confidence interval: 28.9-36.1) and 27.9% (95% confidence interval: 24.5-31.3), respectively. In the multiple regression model for this group, myopia strongly correlated with cataract (odds ratio = 1.98 and 95% confidence interval: 1.33-2.93), and hyperopia only correlated with age (P < 0.001). The prevalence of high myopia and high hyperopia was 1.5% and 4.6%. In the multiple regression model, anisometropia significantly correlated with age (odds ratio = 1.04) and cataract (odds ratio = 5.2) (P < 0.001).

CONCLUSION

The prevalence of myopia and anisometropia was higher than that in previous studies in urban population of Iran, especially in the elderly. Cataract was the only variable that correlated with myopia and anisometropia.

Cohort profile: Shahroud Eye Cohort Study

The Shahroud Eye Cohort Study was set up to determine the prevalence and incidence of visual impairment and major eye conditions in the 40-64-year-old population of Shahroud as a Middle Eastern population. The first phase of the study was conducted in 2009-10. Using random cluster sampling, 6311 Shahroud inhabitants were invited for ophthalmologic examinations; of these, 5190 participants completed phase 1 (participation rate of 82.2%). All participants were interviewed to collect data on participants' demographics, occupation status, socioeconomic status, history of smoking, and medical and ophthalmic history, as well as history of medication, and the quality and duration of their insurance. DNA and plasma samples, as well as four dots of whole blood were collected from participants. Extensive optometric and ophthalmologic examinations were performed for each participant, including lensometry of current glasses, testing near and far visual acuity; determining objective and subjective refraction; eye motility; cycloplegic refraction; colour vision test; slit-lamp biomicroscopy and intraocular pressure measurement; direct and indirect fundoscopy; perimetry test; ocular biometry; corneal topography; lens and fundus photography; and the Schirmer's (1008 participants) and tear breakup time tests (1013 participants). The study data are available for collaborative research at Noor Ophthalmology Research Center, Tehran, Iran.

The distribution of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth in an adult population of Shahroud, Iran

Background

Ocular biometric parameters can be influenced by race, ethnicity, and genetics; their differences across different populations can probably explain differences in refractive errors in these populations. The aim of this study is to determine the normal range of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth in the population of Shahroud in the north of Iran.

Methods

In the first phase of Shahroud Eye Cohort Study, the 40–64 year old population were sampled cross-sectionally; 6311 were invited and 5190 (82.2%) participated in the study. Biometric examinations were done using the LENSTAR/BioGraph (WaveLight AG, Erlangen, Germany) after vision tests and before cycloplegic refraction tests. Any type of eye surgery, extensive pterygium, and lack of cooperation were used as exclusion criteria, and analyses were done with data from 4869 eyes.

Results

We found a mean axial length of 23.14 mm (95% confidence interval [CI], 23.11-23.17), mean anterior chamber depth of 2.62 mm (95% CI, 2.60-2.63), mean lens thickness of 4.28 mm (95% CI, 4.27-4.29), and the mean vitreous chamber depth was 15.72 mm (95% CI, 15.70-15.75).

Kolmogorov-Smirnov tests showed that the distribution of axial length, anterior chamber depth, lens thickness, and vitreous chamber depth significantly differed from normal; axial length and vitreous chamber depth demonstrated a leptokurtic distribution as well.

Axial length, anterior chamber depth, and vitreous chamber depth significantly decreased with age, and lens thickness significantly increased with age (p < 0.001). All indices were significantly higher in men.

Conclusions

The distributions of axial length, vitreous chamber depth, and lens thickness are reported for the first time in an Iranian adult population. Compared to other studies, axial length was in the mid range, nonetheless, studying axial length components showed that the Iranian population had smaller anterior chamber depth and lens thickness. Age and gender were significantly associated with all indices assessed in this study.