The Tehran Eye Study: research design and eye examination protocol

Mean cycloplegic refractive error in emmetropic adults - The Tehran Eye Study

PURPOSE

In children under 20 years, refractive development targets a cycloplegic refractive error of +0.5 to +1.5D, while presbyopes over 40 years generally have non-cycloplegic errors of ≥ +1D. Some papers suggest these periods are separated by a period of myopic refractive error (i.e., ≤ -0.50D), but this remains unclear. Hence, this work investigates the mean cycloplegic refractive error in adults aged between 20 - 40 years.

METHODS

In 2002 a cross-sectional study with stratified cluster sampling was performed on the population of Tehran, providing cycloplegic and non-cycloplegic refractive error data for the right eyes of 3,576 participants, aged 30.6±18.6 years (range: 1-86 years). After grouping these data into age groups of 5 years, the refractive error histogram of each group was fitted to a Bigaussian function. The mean of the central, emmetropized peak was used to estimate the mean refractive error without the influence of myopia.

RESULTS

The mean cycloplegic refractive error at the emmetropized peak decreased from +1.10±0.11D (95 % confidence interval) to +0.50±0.04D before 20 years and remains stable at that value until the age of 50 years. The non-cycloplegic refractive error also sees a stable phase at 0.00±0.04D between 15 - 45 years. After 45 - 50 years both cycloplegic and non-cycloplegic refractive error become more hypermetropic over time, +1.14±0.12D at 75 years.

CONCLUSIONS

The cycloplegic refractive error in adults is about +0.50D between 20 - 50 years, disproving the existence of the myopic period at those ages.

The Sleep Health of Individuals with Visual Impairments: A Scoping Review

PURPOSE

Amidst the global aging population and an increasing prevalence of visual impairment across all age groups, this study aims to investigate the current state of research on sleep health in visually impaired populations.

METHODS

A scoping review was conducted to synthesize the existing literature on sleep health and visual impairment. We employed conceptual mapping to identify key research topics, analyzing data from four databases: PubMed (n = 290), CINAHL (n = 81), Scopus (n = 117), and PsycInfo (n = 96). A total of 83 peer-reviewed articles, published from 1977 to August 2023, were included in the review.

RESULTS

Our analysis identified 11 distinct eye health conditions including blindness, glaucoma, diabetic retinopathy, low vision, cataract, retinitis pigmentosa, macular degeneration, optic neuropathy, visual field defects, ocular hypertension, and retinal vein occlusion. Additionally, 8 major sleep problems were recognized: abnormal sleep duration, daytime sleepiness, insomnia, Non-24-Hour Sleep Wake Disorder, sleep apnea, sleep disorders, sleep disturbances, and sleep disordered breathing. The dominant research themes were (1) poor sleep quality in individuals with visual impairments and ophthalmic diseases, (2) high prevalence of sleep issues in patients with ophthalmic diseases, (3) sleep apnea in patients with ophthalmic conditions, and (4) circadian rhythm disruptions in blind individuals.

CONCLUSION

This review highlights research gaps that, when addressed, could greatly enhance our comprehension of the interplay between visual impairment and sleep health. Bridging these gaps promises to lead to more holistic care strategies, potentially improving vision functioning and rehabilitation outcomes for individuals with visual impairments.

Role of family factors in provision and perception of social support for older people in Iran: a cross-sectional survey

BACKGROUND

Iran has experienced a very fast fertility transition. The process of demographic transition, coupled with modernization, has had considerable consequences for the structure and function of families. There is rising concern in Iran about a potential decline in family care and support for older people as a result of these changes. The main aim of this study was to provide a benchmark by examining current associations between family factors and older people's social support, both perceived and received.

METHODS

A cross-sectional survey of a random sample of 644 people aged 60 + years resident in Tehran was conducted using stratified cluster random sampling method in 2015. Outcome variables were perceived social support, as measured by Social Provision Scale, and received instrumental social support. Multilevel mixed-effects models were used to examine the hypotheses.

RESULTS

The analyses showed that most of the family factors measured, including family size (p = 0.01), living arrangements (p = 0.05), and amount of contact with family members (p = 0.001) were associated with older people's receipt of instrumental social support. Living arrangements and quality of relationships with family members were associated with older people's perceptions of social support (p < 0.001). Also, a significant gender interaction was found in associations between family size and SPS (p = 0.03). Having a large size family was positively associated with higher SPS for women (Coef. = 3.9, p = 0.009) but not for men (Coef. = -0.4, p = 0.7).

CONCLUSION

findings of this study support the premise that most of family factors play an important role in provision and perception of social support for Iranian older people. Further policies should mostly be selective of those at higher risk of low support such as widowed, childless, those living alone, having poor relationship with their relatives and those with worse health status. The results of this study may be utilized to target older populations who are at higher risk of low support with innovative programs that focus on building social networks and enhancing social support.

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.

AZAR eye and vision cohort study

According to World Health Organization (WHO), currently, 2.2 billion people are living with visual impairment worldwide, of which almost half could have been prevented. There are both modifiable and unmodifiable factors leading to visual disability and, ultimately, blindness. Several population-based studies in different parts of Iran have tried to determine these factors concerning their specific population and environment-related characteristics. AZAR Eye and Vision cohort is the second-largest cohort study in the whole country. AZAR Eye and Vision cohort is the ophthalmologic branch of AZAR cohort which is the largest eye cohort study in the country, which is trying to determine the prevalence and incidence of visual impairment, blindness, and other major ophthalmologic conditions and their associated risk factors in East Azerbaijan province located in Iran, a middle eastern country. A recently emerging phenomenon is the drying of the ultra-salty lake of Urmia located in the West Azerbaijan province which is a direct neighbor of our studied population and has caused recurrent salt storms in the immediate near areas. This phenomenon could adversely affect visual health via different conditions which our study will elucidate. The enrollment phase took place between 2014 and 2017 and 11,208 participants were enrolled out of 15,000 participants in the primary cohort. The resurvey phase will begin five years after the enrollment phase. In this phase, 30% of the participants are randomly selected to be reexamined and complete questionnaires. The participants showing any issues such as diabetes and being a glaucoma suspect will be included in the resurvey phase, too. Data categories gathered include demographics, lifestyle factors, past medical and drug histories, and a diet quality and quantity questionnaire including 130 edible items. Urine, hair, nail, and 25-ml blood samples, were collected from the participants. Then they were referred to an optometrist to complete an ophthalmologic questionnaire and undergo eye examination and lensometry. Then they underwent slit-lamp examinations and pictures were taken of the lens and fundus. People with suspected visual impairment were referred to an ophthalmology clinic. The data are processed and a four-level quality check is performed on each block. The most common visual impairment is cataracts. This study's most important aim is to evaluate the effect of local environmental and ethnic factors on eye diseases in this specific population.

Evaluation of Ocular Higher-Order Aberrations in First-Degree Relatives of Patients With Keratoconus

PURPOSE

The aim of this study was to evaluate the corneal higher-order aberrations (HOAs) in first-degree relatives of patients with keratoconus (KCN) and compare with the normal population.

METHODS

In this prospective comparative study, 210 eyes from 105 family members of 28 patients with KCN and 210 normal eyes of 105 controls were enrolled. In each eye, corneal topography, tomography, and aberrometry were performed and compared between the 2 groups.

RESULTS

This study included 61 female (58.1%) and 44 male participants (41.9%) and 105 age-matched and sex-matched controls with normal topographic cornea. In 14 of 105 first-degree relatives (13.33%) of patients with KCN, KCN was diagnosed with a male preponderance (71.5% male, 28.5% female). Tomographic indices and irregularity indices in 3 and 5 mm zone in Orbscan were significantly higher in the relative group. In addition, other irregularity indices of TMS-4 topography including surface regularity index, surface asymmetry index, difference sector index, SDP, and irregular astigmatism index were significantly higher in family members of patients with KCN. The most prevalent topographic pattern in the control group was the symmetric bowtie (57.1%) and in the relative group was the asymmetric bowtie (39.5%). In addition, significantly thinnest corneal pachymetry was detected in the relative group. Root mean square of all HOAs including vertical trefoil, vertical coma, horizontal coma, horizontal trefoil, quadrifoil, and fourth-order spherical aberrations were significantly greater in the relative group than controls.

CONCLUSIONS

Owing to the high prevalence of undiagnosed KCN susceptibility in family members with KCN, keratorefractive surgery should be considered cautiously in these individuals. In addition, comprehensive preoperative examination should be considered to detect subtle topographic and HOAs in these individuals.

Gender Interaction in Association of Perceived Social Support and Health-Related Quality of Life Among Iranian Older People: A Cross-sectional Survey

Background: The purpose of this study was to examine the relationship between perceived social support (PSS) and dimensions of health-related quality of life (HRQoL) and to examine possible gender interaction in the mentioned associations. Methods: A community-based cross-sectional study conducted among 644 participants over the age of 60 years old in Tehran. The data were collected through face-to-face interviews conducted in their own homes, by using a structured multi-sectional questionnaire. The version 1 of the SF-12 scale was used to measure the HRQoL, consisting of two summary measures; PCS (Physical Component Score) and MCS (Mental Component Score). The Persian version of the Social Provisions Scale (SPS) was used to measure PSS. Four multilevel mixed-effects logistic regression models were used to examine the associations. Results: Older people with poor SPS score were 1.8 times more likely to be in the worst quartile of the MCS distribution (CI=1.11-2.93, P =0.021), and twice as likely to be in the worst quartile of the PCS distribution (CI=1.18-3.54, P =0.011). We found strong evidence to support the hypothesis of gender interaction in the association between economic status and PCS [Men: OR 0.28, CI (0.11-0.71); Women: OR 1.00, CI (0.53-1.88); P of Interaction 0.021], and a borderline evidence for gender interaction in the association between physical activity and PCS [Men: OR 5.32, CI (2.14-13.20); Women: OR 1.80, CI (0.82-3.93); P of Interaction 0.051]. Conclusions: Social support could be regarded as one of the main social determinants affecting HRQoL among older people. Men with poor economic status and poor physical activity, compared to women, are more likely to suffer from poor quality of life, thus men should be prioritized in financial support and life style and physical activity interventions.

Prevalence of Color Vision Deficiency in an Adult Population in South Korea

SIGNIFICANCE

Large differences in failure rates for color vision screening have been reported among different regional groups. However, color vision deficiency prevalence in Korea has only been investigated within a small area of the country.

PURPOSE

This study examines the prevalence of failing a color vision screening and its sex-related differences using a sample that is representative of the whole Korean population.

METHODS

This population-based cross-sectional study evaluated 2686 subjects (age, 19 to 49 years) who participated in the sixth Korea National Health and Nutrition Examination Survey (2013). Color vision deficiency was assessed using the Hardy-Rand-Rittler (HRR) test by an ophthalmologist. According to standard criteria for the HRR, it classified each subject as color normal, protan, deutan, tritan, or unclassified color vision loss. All participants had comprehensive medical evaluations and ocular history taken.

RESULTS

The weighted overall prevalence of color vision deficiency in the Korean population was 3.9% (95% confidence interval, 3.0 to 5.4%). The prevalence of color vision deficiency was higher in male participants (6.5%) than in female participants (1.1%). Among all participants, deutan deficiency (2.5%) had a higher prevalence than did protan deficiency (0.4%). For male participants who failed the HRR screening, deutan-type deficiency was detected most often (64.2%), whereas an unclassified color vision deficiency type was the most common (52.9%) among female participants who failed the HRR screening. As expected, male participants were more likely to fail the HRR screening compared with female participants (prevalence ratio, 6.08; 95% confidence interval, 3.61 to 10.26).

CONCLUSIONS

This large population-based study of color vision deficiency among Koreans gives the most accurate estimate of failing a color vision screening test to date and provides useful information for planning adaptive strategies.

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 Shiraz Pediatric Eye Study; a Population Based Survey of School Age Children: Rationale, Design and Baseline Characteristics

Purpose:

To describe the rationale, study design, methodology, and baseline characteristics of the Shiraz Pediatric Eye Study, a population-based survey of schoolchildren in Shiraz, Iran.

Methods:

This population-based study included schoolchildren aged 6–12 years from all four educational districts of Shiraz who were recruited in years 2015–2016. Stratified random sampling was used to select 2400 participants from all districts. Data were recorded from a detailed interview and ocular evaluation of each eligible student. The eye examination comprised uncorrected and best corrected visual acuity measurement, refraction, external eye examination (including specific strabismus and lid evaluation tests), slit lamp biomicroscopy, intraocular pressure measurement, the Ishihara color vision test, and stereoacuity. Exophthalmometry, optical biometry, and optical coherence tomography were performed for a randomly selected subset of children. General characteristics and socioeconomic variables were also recorded to assess risk factors.

Results:

From a total of 2400 selected students, 2001 (83.3%) participated in the study. The mean age of the students was 9.1 ± 1.6 years, and 59.7% were girls. Most children had at least one parent with a diploma or less than diploma (63.5%), and 2.2% had illiterate parents.

Conclusion:

This study is expected to provide accurate estimates of the prevalence of visual impairments and their related determinants in Shiraz. In addition, it will identify children who should be targeted by blindness prevention programs.

Distribution of iris color and its association with ocular diseases in a rural population of Iran

Purpose

To determine the distribution of iris color and its relationship with some ocular diseases in a rural population of Iran.

Methods

Two rural areas of the north and southwest of Iran were selected by a cross-sectional study using multi-stage cluster sampling. After selecting samples, the participants had an eye examination including measuring visual acuity, refraction, and Pentacam imaging. Then an eye examination for individuals was performed by slit-lamp.

Results

Out of 3851 invited people, 3314 participated in this study (participation rate, 86.05%). Dark brown [41.28%, confidence interval (CI) 95% = 31.88–50.68] and blue (0.99%, CI 95% = 0.57–1.41) were the most and the least type of iris colors among participants of this study. Compared to others, people with a dark iris have the biggest anterior chamber depth (ACD), angle and volume while central corneal thickness (CCT), keratometry and pupil were highest among people with a dark brown iris (P < 0.002). Considering the dark brown group as a base group, the chances of being afflicted to cataract among people with dark, light brown, green, and blue irises are 1.89 (CI 95% = 1.25–2.86), 1.53 (CI 95% = 1.17–2.01), 4.60 (CI 95% = 2.17–9.71), and 12.17 (CI 95% = 5.05–29.31), respectively. The chance of being afflicted to myopia among people with green irises and to hyperopia among people with blue irises were high (1.60, CI 95% = 1.08–2.36 and 3.20, CI 95% = 1.03–9.97, respectively).

Conclusions

Dark brown was the most prevalent iris color in rural areas of Iran. The index of cornea among people with dark and dark brown iris color is higher than other people, and people with light iris color are at a higher risk of developing eye disease such as cataract, corneal opacity, and refractive error. To determine this relationship and its usage for therapeutic and public health purposes, further studies are recommended.

Social support and mental health status of older people: a population-based study in Iran-Tehran

OBJECTIVES

To investigate direct and stress-buffering associations between social support from family and the mental health of older people in Iran, a country which has recently undergone an exceptionally fast fertility transition and is consequently experiencing rapid population ageing.

METHOD

A cross-sectional stratified random survey of 800 people aged 60+ years resident in Tehran was conducted. In total, 644 people responded. The Social Provisions Scale and the General Health Questionnaire were used to measure perceived social support and mental health, respectively. Multilevel mixed-effects models were used to examine the hypotheses.

RESULTS

The findings supported the hypothesis of a direct association between perceived and received social support and mental health. However, we did not find strong evidence to suggest that social support buffered the effects of stress arising from limitations of physical functioning. Lack of help doing paperwork was associated with worse mental health for women but not men. Source of support did not seem to be important.

CONCLUSION

Our results indicated that in Tehran, as in Western settings, social support is important for the mental well-being of older people. Recommendations for policy and further research priorities based on the study findings were provided.

Evidence for the need for vision screening of school children in Turkey

BACKGROUND

In many countries, access to general health and eye care is related to an individual's socioeconomic status (SES). We aimed to examine the prevalence of oculo-visual disorders in children in Istanbul Turkey, drawn from schools at SES extremes but geographically nearby.

METHODS

Three school-based vision screenings (presenting distance visual acuity, cover test, eye assessment history, colour vision, gross stereopsis and non-cycloplegic autorefraction) were conducted on 81% of a potential 1014 primary-school children aged 4-10 years from two private (high SES) schools and a nearby government (low SES) school in central Istanbul. Prevalence of refractive errors and school-based differences were analysed using parametric statistics (ANOVA). The remaining oculo-visual aspects were compared using non-parametric tests.

RESULTS

Of the 823 children with mean age 6.7 ± 2.2 years, approximately 10% were referred for a full eye examination (8.2% and 16.3% of private/government schools respectively). Vision had not been previously examined in nearly 22% of private school children and 65% of government school children. Of all children, 94.5% were able to accurately identify the 6/9.5 [LogMAR 0.2] line of letters/shapes with each eye and 86.6% the 6/6 line [LogMAR 0], while 7.9% presented wearing spectacles, 3.8% had impaired colour vision, 1.5% had grossly impaired stereo-vision, 1.5% exhibited strabismus, 1.8% were suspected to have amblyopia and 0.5% had reduced acuity of likely organic origin. Of the 804 without strabismus, amblyopia or organic conditions, 6.0% were myopic ≤ - 0.50DS, 0.6% hyperopic ≥ + 2.00DS, 7.7% astigmatic ≥1.00 DC and 6.2% anisometropic ≥1.00DS.

CONCLUSIONS

The results highlight the need for general vision screenings for all children prior to school entry given the varied and different pattern of visual problems associated with lifestyle differences in two populations raised in the same urban locale but drawn from different socioeconomic backgrounds.

Time and frequency components of ERG responses in retinitis pigmentosa

PURPOSE

To evaluate the effects of retinitis pigmentosa (RP) on time, frequency, and time-frequency components of Xenon flash ERG signals using Fourier and wavelet transforms.

METHODS

Xenon flash ERG was done in 18 eyes of nine RP patients and 20 normal eyes. After examining latency and amplitude, Fourier and wavelet transforms were performed using MATLAB software. Then, we extracted the mode frequency from the Fourier transform and main frequencies and their occurrence time from the wavelet transform. Finally, mean differences were analyzed using statistical tests.

RESULTS

The results indicated increased latency and reduced ERG wave amplitude, no significant inter-group difference in the average mode frequency, and significant reduction in main signal frequencies and their increased occurrence times. Also one or two of the three main frequencies had disappeared in more advanced cases.

CONCLUSION

Retinitis pigmentosa can induce changes in ERG time and time-frequency components. Impacted areas can be identified more accurately by wavelet transform and converting scales to frequencies.

Cycloplegic autorefraction versus subjective refraction: the Tehran Eye Study

AIM

To compare cycloplegic autorefraction with non-cycloplegic subjective refraction across all age and refractive error groups.

METHODS

In a cross-sectional study with random stratified cluster sampling, 160 clusters were chosen from various districts proportionate to the population of each district in Tehran. Following retinoscopy and autorefraction with the 0.25 D bracketing (Topcon KR-8000, Topcon, Tokyo, Japan), all participants had a subjective refraction. Then all participants underwent cycloplegic autorefraction.

RESULTS

The final analysis was performed on 3482 participants with a mean age of 31.7 years (range 5-92 years). Based on cycloplegic and subjective refraction, mean spherical equivalent (SE) was +0.31±1.80 and -0.32±1.61 D, respectively (p<0.001). The 95% limits of agreement (LoA) between these two types of refraction were from -0.40 to 1.70 D. The largest difference between these two types of refraction was seen in the age group of 5-10 years (1.11±0.60 D), and the smallest difference was in the age group of >70 years (0.34±0.45 D). The 95% LoA was -0.52 to 0.89 D in patients with myopia and -0.12 to 2.04 D in patients with hyperopia. We found that female gender (coefficients=0.048), older age (coefficients=-0.247), higher education (coefficients=-0.043) and cycloplegic SE (coefficients=-0.472) significantly correlated with lower intermethod differences.

CONCLUSIONS

The cycloplegic refraction is more sensitive than the subjective one to measure refractive error at all age groups especially in children and young adults. The cyclorefraction technique is highly recommended to exactly measure the refractive error in momentous conditions such as refractive surgery, epidemiological researches and amblyopia therapy, especially in hypermetropic eyes and paediatric cases.

The frequency of occurrence of certain corneal conditions by age and sex in Iranian adults

PURPOSE

To determine the prevalence of posterior embryotoxon, corneal opacity, pigment on endothelium, corneal dystrophy, and corneal vascularization in a middle-aged Iranian population, and their association with age and sex.

METHODS

In a cross-sectional study with multistage cluster sampling, subjects were chosen from 40 to 64-year-old residents of Shahroud in northern Iran. Participants had ophthalmic examinations before and after pupil dilation. Corneal abnormalities were diagnosed by an ophthalmologist using a slit lamp.

RESULTS

Of the 6311 invitees, 5190 people (82.2%) participated; 58.6% (n=3040) were female. The prevalence of posterior embryotoxon, corneal opacity, and pigment on endothelium were 14.7% (95% CI: 13.4-16.0), 4.1% (95% CI: 3.4-4.7) and 1.2% (95% CI: 0.9-1.5), respectively, and corneal dystrophy and corneal vascularization were seen in 0.3% (95% CI: 0.2-0.5) and 3.7% (95% CI: 3.0-4.3), respectively. Unlike posterior embryotoxon, the prevalence of all studied abnormalities increased with age after adjusting for sex. The prevalence of posterior embryotoxon (p=0.023) and corneal dystrophy (p=0.038) was significantly higher in women, and the prevalence of corneal opacity (p<0.001) was significantly higher in men. After adjusting for age, sex, and cataract, cases with corneal opacity and corneal vascularization demonstrated significantly worse uncorrected and corrected visual acuity (p<0.001).

CONCLUSION

This report is the first to explore the prevalence of a variety of corneal conditions in a Middle-Eastern population. The findings indicate that one out of five people may have some sort of corneal conditions, and some can impact corrected visual acuity.

Crystalline lens and refractive development

Individual refractive errors usually change along lifespan. Most children are hyperopic in early life. This hyperopia is usually lost during growth years, leading to emmetropia in adults, but myopia also develops in children during school years or during early adult life. Those subjects who remain emmetropic are prone to have hyperopic shifts in middle life. And even later, at older ages, myopic shifts are developed with nuclear cataract. The eye grows from 15 mm in premature newborns to approximately 24 mm in early adult years, but, in most cases, refractions are maintained stable in a clustered distribution. This growth in axial length would represent a refractive change of more than 40 diopters, which is compensated by changes in corneal and lens powers. The process which maintains the balance between the ocular components of refraction during growth is still under study. As the lens power cannot be measured in vivo, but can only be calculated based on the other ocular components, there have not been many studies of lens power in humans. Yet, recent studies have confirmed that the lens loses power during growth in children, and that hyperopic and myopic shifts in adulthood may be also produced by changes in the lens. These studies in children and adults give a picture of the changing power of the lens along lifespan. Other recent studies about the growth of the lens and the complexity of its internal structure give clues about how these changes in lens power are produced along life.

Corneal topography patterns in the Tehran eye study: warning about the high prevalence of patterns with a skewed radial axis

Purpose:

The purpose of this study is to determine the distribution of corneal topography patterns in Tehran.

Materials and Methods:

In this population-based study, a total of 442 individuals were randomly selected by cluster sampling for complete ophthalmologic examination. A total of 404 (788 eyes) met the inclusion criteria and were enrolled in this study. Orbscan II (Bausch and Lomb Surgical, Salt Lake City, USA) was used to determine the anterior segment indices and axial power maps for each eye.

Results:

On the basis of the axial power maps, the symmetric bowtie (SB) (29.0%) and asymmetric bowtie with inferior steepening (16.7%) patterns were the most prevalent and the irregular (3.3%) and superior steepening (1.5%) patterns the least prevalent. Asymmetric bowtie pattern with a skewed radial axis (AB-SRAX) was seen in 7.6% of eyes. These cases had both thinner and steeper corneas compared with round and SB ones (P < 0.014 and P < 0.006). Maximum anterior elevation in 5 mm zone, of AB-SRAX corneas were higher than other patterns (P < 0.01) except for superior steepened and inferior steepened ones.

Conclusions:

The distribution of corneal topographic patterns in Iranians seems like other Asian population on the whole. The 7.6% prevalence of AB-SRAX patterns may be a warning on keratoconus prevalence in our population. This is in line with recent regional reports.

Analysis of familial aggregation in total, against-the-rule, with-the-rule, and oblique astigmatism by conditional and marginal models in the Tehran eye study

Purpose:

The purpose was to determine the familial aggregation of the total, against-the-rule (ATR), with-the-rule (WTR), and oblique astigmatism by conditional and marginal models in the Tehran Eye Study.

Materials and Methods:

Total, ATR, WTR, and oblique astigmatism were studied in 3806 participants older than 5 years from August 2002 to December 2002 in the Tehran Eye Study. Astigmatism was defined as a cylinder worse than or equal to −0.5 D. WTR astigmatism was defined as 0 ± 19°, ATR astigmatism was defined as 90 ± 19°, and oblique when the axes were 20–70° and 110–160°. The familial aggregation was investigated with a conditional model (quadratic exponential) and marginal model (alternating logistic regression) after controlling for confounders.

Results:

Using the conditional model, the conditional familial aggregation odds ratios (OR) (95% confidence interval) for the total, WTR, ATRs, and oblique astigmatism were 1.49 (1.43–1.72), 1.91 (1.65–2.20), 2.00 (1.70–2.30), and 1.86 (1.37–2.54), respectively. In the marginal model, the marginal OR of the parent-offspring and sib-sib in the total astigmatism were 1.35 (1.13–1.63) and 1.54 (1.13–2.11), respectively; WTR 1.53 (1.06–2.20) and 1.94 (1.21–3.13) and; ATR 2.13 (1.01–4.50) and 2.23 (1.52-3.30). The model was statistically significant in sib-sib relationship only for oblique astigmatism with OR of 3.00 (1.25–7.20).

Conclusion:

The results indicate familial aggregation of astigmatism in the population in Tehran adjusted for age, gender, cataract, duration of education, and body mass index, so that the addition of a new family member affected with astigmatism, as well as having a sibling or parents with astigmatism, significantly increases the odds of exposure to the disease for all four phenotypes. This aggregation can be due to genetic and/or environmental factors. Dividing astigmatism into three phenotypes increased the odds ratios.

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.

Prevalence and risk factors for anisometropia in the Tehran eye study, Iran

PURPOSE

To determine the prevalence of anisometropia and its determinants in a population-based sample.

METHODS

In a cross-sectional population-based study, stratified cluster sampling was carried out from the population of Tehran. Respondents were transferred to a clinic for an interview and ophthalmic examinations including tests for visual acuity with and without correction, cycloplegic refraction, the slit lamp examination, fundoscopy, and lensometry. Anisometropia was defined as unequal spherical equivalent cycloplegic refractions in the two eyes.

RESULTS

Of 4565 participants, cycloplegic refraction was performed in both eyes of 3519 people. The mean age of the examinees was 31.5 ± 18.0 (range, 5-86) years. The mean anisometropia was 0.34 diopter (D) (95% Confidence Interval (CI): 0.31-0.37). The prevalence rates of anisometropia more than 0.5, 1.0, 1.5 and 2.0 D were 18.5% (95% CI: 17.0-19.9), 6.7% (95% CI: 5.8-7.7), 3.8% (95% CI: 3.1-4.5) and 2.6% (95% CI: 2.1-3.1). The inter-gender difference in the prevalence of anisometropia ≥ 1.0D was not statistically significant (P = 0.952). The prevalence of anisometropia increased after the age of 45 years. Overall, 15.7% of the examinees had anisomyopia and 4.7% had anisohypermetropia equal to or more than 1.0D. Anisometropia was more prevalent among patients with cataracts, amblyopia, and pseudophakia. The prevalence rates of spherical and cylindrical anisometropia in the studied sample were 8.0% and 7.1%, respectively.

CONCLUSIONS

The prevalence of anisometropia in the population of Tehran is beyond negligible. It showed a significant increase with age. Results also indicate that myopic patients are more likely to have anisometropia.

The association between refractive errors and cataract: the tehran eye study

Purpose:

To determine the association between refractive errors and different types of cataract in Tehran, Iran.

Materials and Methods:

In a cross-sectional survey with a stratified cluster sampling approach, refractive errors were tested under cycloplegia. Myopia and hyperopia were defined as a spherical equivalent refractive error <-0.5 diopters (D) and more than +0.5 D, respectively. Cataract was graded according to the Lens Opacities Classification System III classification and the association between refractive errors and cataract was assessed. Of 1434 participants over the age of 40 years who participated in the study, data from 1313 right eyes were analyzed.

Results:

The mean age of the participants was 52.7 ± 10.0 years, and 58.3% (n = 767) were female. Overall, myopia was more prevalent among those with cataract (odds ratio [OR]: 2.00, 95% confidence interval [CI]: 1.38–2.89). Based on the type of cataract and refractive errors, the odds of myopia was significantly higher with nuclear cataracts (OR: 1.81, 95% CI: 1.14–2.87). The odds of myopia was higher for cases of nuclear cataract with some degrees of posterior subcapsular cataract (PSC) (OR: 3.33, 95% CI: 1.42–7.80). Of nine participants with cortical cataract, seven participants had hyperopia (OR: 3.77, 95% CI: 0.78–18.31).

Conclusion:

Individuals with nuclear and PSC showed a significantly higher prevalence of myopia while the prevalence of hyperopia was lower in those with cataract. High myopia was seen in higher grades of nuclear cataract. The high percentage of hyperopia was also significant in patients with cortical cataract. More studies are necessary to clarify the correlation between cortical cataract and hyperopia.

Prevalence of congenital color vision defects in Saudi females of Arab origin

BACKGROUND

Inherited color vision deficiencies (CVD) vary in prevalence by population and by sex. The most common CVD is X chromosome-linked anomalous trichromacy. Prevalence varies significantly by sex and race. The frequency of color vision defects in Saudi females has not been studied previously. This study surveyed the prevalence of congenital color vision defects in Saudi females of Arab origin.

METHODS

Seven thousand four hundred sixty-seven female subjects (N = 7,467) from the Kingdom of Saudi Arabia were screened using both Ishihara pseudoisochromatic plates and the Farnsworth Dichotomous test (D-15). CVD subjects were tested further with the Farnsworth-Munsell 100 Hue test.

RESULTS

Of 7,467 female subjects tested, 26 subjects were found to have defective color vision, for a prevalence of 0.35%. Sixteen subjects had a deutan defect, and 10 had a protan defect. Arab females have significantly lower prevalence of CVD when compared with published data from females of other races. Analysis of the 5 regions of Saudi Arabia showed no significant difference between the regions.

CONCLUSION

Prevalence of CVD among Saudi females of Arab origin is 0.35% and is among the lowest of all published data.

Refractive errors in students from Middle Eastern backgrounds living and undertaking schooling in Australia

BACKGROUND

  Environmental factors associated with schooling systems in various countries have been implicated in the rising prevalence of myopia, making the comparison of prevalence of refractive errors in migrant populations of interest. This study aims to determine the prevalence of refractive errors in children of Middle Eastern descent, raised and living in urban Australia but actively maintaining strong ties to their ethnic culture, and to compare them with those in the Middle East where myopia prevalence is generally low.

METHODS

  A total of 354 out of a possible 384 late primary/early secondary schoolchildren attending a private school attracting children of Middle Eastern background in Melbourne were assessed for refractive error and visual acuity. A Shin Nippon open-field NVision-K5001 autorefractor was used to carry out non-cycloplegic autorefraction while viewing a distant target. For statistical analyses students were divided into three age groups: 10-11 years (n = 93); 12-13 years (n = 158); and 14-15 years (n = 102).

RESULTS

  All children were bilingual and classified as of Middle Eastern (96.3 per cent) or Egyptian (3.7 per cent) origin. Ages ranged from 10 to 15 years, with a mean of 13.17 ± 0.8 (SEM) years. Mean spherical equivalent refraction (SER) for the right eye was +0.09 ± 0.07 D (SEM) with a range from -7.77 D to +5.85 D. The prevalence of myopia, defined as a spherical equivalent refraction 0.50 D or more of myopia, was 14.7 per cent. The prevalence of hyperopia, defined as a spherical equivalent refraction of +0.75 D or greater, was 16.4 per cent, while hyperopia of +1.50 D or greater was 5.4 per cent. A significant difference in SER was seen as a function of age; however, no significant gender difference was seen.

CONCLUSIONS

  This is the first study to report the prevalence of refractive errors for second-generation Australian schoolchildren coming from a predominantly Lebanese Middle Eastern Arabic background, who endeavour to maintain their ethnic ties. The relatively low prevalence of myopia is similar to that found for other metropolitan Australian school children but higher than that reported in the Middle East. These results suggest that lifestyle and educational practices may be a significant influence in the progression of myopic refractive errors.

White-to-white corneal diameter in the Tehran Eye Study

PURPOSE

To determine the mean corneal diameter and its determinants in the population of Tehran.

METHODS

From the Tehran Eye Study participants who were sampled through a stratified cluster approach, those in the first 4 municipality districts of Tehran were selected, and after applying the inclusion and exclusion criteria, 399 right eyes and 401 left eyes of 410 people aged 14 years and older were examined with the Orbscan II. The corneal diameter was defined as the horizontal limbus-to-limbus distance. Linear regression was used to detect separate and multiple correlations. The design effect of cluster sampling was also considered and adjusted for.

RESULTS

The studied participants were male in 38.80%, and their mean age was 40.68 +/- 16.80 years. The mean corneal diameter was 11.68 mm (95% confidence interval: 11.63-11.73). The 95% range (mean +/- 2 SDs) was 10.76-12.60 mm. The mean corneal diameter was 11.76 and 11.63 mm in males and females, respectively. The corneal diameter in the studied population had no significant correlation with age (P = 0.186) but showed an increase of 0.18 mm for each millimeter increase in the anterior chamber depth (P = 0.028).

CONCLUSION

Although the mean corneal diameter in the present population was not different from that reported in other studies, the data suggest that slightly different cutoff values for the definition of macrocornea (>12.60 mm) and microcornea (<10.76 mm) can be used with this population.

Distribution of angle kappa measurements with Orbscan II in a population-based survey

PURPOSE

To determine the mean angle kappa and its determinants in the population of Tehran, Iran.

METHODS

In a cross-sectional survey with random cluster sampling, a total of 442 participants aged >14 years were selected from 4 municipality districts of Tehran for Orbscan acquisitions. Exclusion criteria were history of eye surgery for refractive errors, cataract or glaucoma, and use of topical medication or any type of contact lens at the time of the study. Mean angle kappa in different age and gender groups and its association with other factors was assessed. Considering the high correlation between the right and left eyes, only results of the right eyes are presented.

RESULTS

After applying exclusion criteria, 800 eyes (399 right eyes and 401 left eyes) were examined. Mean participant age was 40.6±16.8 years (range: 14 to 81 years), and 38.8% of eyes were from men. Mean angle kappa was 5.46±1.33° in total; 5.41±1.32° in men and 5.49±1.34° in women (P=.558). It decreased significantly with age; 0.015°/year (P<.001). In individuals with myopia, emmetropia, and hypermetropia, the mean value was 5.13±1.50°, 5.72±1.10°, and 5.52±1.19°, respectively (P=.025); the post-hoc test indicated this was due to the difference between emmetropes and myopes.

CONCLUSIONS

According to our results, angle kappa reduces with age, and the inter-gender difference is not significant. Largest angle kappas were seen among individuals with emmetropia. Angle kappas were larger in the hypermetropic population compared to the myopic population.

Astigmatism and its Determinants in the Tehran Population: The Tehran Eye Study

PURPOSE

To determine the prevalence of astigmatism and its epidemiological risk factors in Tehran via a population-based study.

METHODS

By means of a stratified random cluster sampling, 6497 citizens representing a cross-section of the population of Tehran were selected from 160 clusters. Eligible people were recruited through a door-to-door household survey in the selected clusters and transferred to a clinic for an extensive eye examination and interview. The refractive status was determined with manifest refraction. Astigmatism was defined as cylinder worse than or equal to 0.5 D. High astigmatism was defined as a manifest cylinder > or =1.5 D.

RESULTS

Between August and December 2002, 4565 of the 6497 eligible individuals in the sample attended the interview and ophthalmic examination (a participation rate of 70.3%). The age- and gender-standardized prevalence of astigmatism was 50.2% (95% CI, 48.4% to 51.9%) on manifest refraction. High astigmatism was found in 490 right eyes (11.1%; 95% CI, 10.1% to 12.0%). Of 2532 participants with ametropia, 59.6 (95% CI, 57.6-61.5) had astigmatism. The percentages of with-the-rule, against-the-rule and oblique astigmatism were 33.6%, 36.9% and 29.3%, respectively. The proportion of type of astigmatism was significantly related to age (p < 0.001). The univariable analysis of astigmatism between family members yielded odds ratios of 1.47 (95% CI, 1.14 to 1.89, p = 0.003) for the association of astigmatism among siblings. After controlling for age, refractive errors and education, the pairwise sibling association remained statistically significant (OR 1.43, 95% CI, 1.08 to 1.88).

CONCLUSION

These findings revealed a high prevalence of astigmatism in the population. Age, education and ametropia were the main predictors of astigmatism in Tehran. Our findings should be considered for case finding and astigmatism correction programs. Our data confirmed a modest familial aggregation for astigmatism.

Distribution of photopic pupil diameter in the Tehran eye study

PURPOSE

To determine the photopic pupil diameter and its determinants in a sample derived from a population-based survey in Tehran.

METHODS

In a cross-sectional study with a stratified random cluster sampling approach, 410 people age 14 years and over were selected from those residing in the first four municipality districts of Tehran after applying exclusion criteria, and 800 eyes (399 right eyes and 401 left eyes) were examined with the Orbscan II. The main outcome measure was the mean pupil diameter under photopic conditions, and possible correlations with potential determinants were evaluated through linear regression analyses. The design effect of a cluster sampling approach was observed and adjusted for.

RESULTS

The mean age of the participants was 40.6 +/- 16.8 years and 38.8% were male. The mean photopic pupil diameter (PPD) was 3.70 mm (range 2.30 to 5.10; 95% confidence interval (CI) 3.62 to 3.78). The mean PPD was 3.67 mm (95% CI, 3.54 to 3.81) in men and 3.72 mm (95% CI, 3.63 to 3.81) in women (p = 0.481). There was a significant reduction of 0.021 mm in PPD per year of aging (r = -0.49, p < 0.001). There was also a significant inverse correlation between PPD and spherical equivalent (r = -0.12, p = 0.034), while there was 0.66-mm increase in PPD with every 1.0-mm increase in the anterior chamber depth (ACD) (p < 0.001). Anisocoria, defined as a pupil diameter difference more than 0.4 mm between two eyes, was observed in 12.2% of the study population.

CONCLUSION

While the mean PPD measured with the Orbscan II was 3.70 mm in a sample derived from a population-based survey in Tehran, the scarcity of similar studies and reports concerning the pupil diameter measured with the Orbscan II makes it difficult to draw eligible comparisons. The pupil diameter has reverse correlations with age and spherical equivalent, a direct correlation with ACD, but is not correlated with gender.

The prevalence of lens opacities in Tehran: the Tehran Eye Study

PURPOSE

To determine the prevalence of lens opacities and cataract surgical coverage among Tehran citizens 40 years of age and older.

METHODS

The Tehran Eye Study was a population-based survey, with random sampling from Tehran household clusters. Those 40 years of age and older from that survey were included in this analysis. All participants underwent full optometric, slit lamp, and fundoscopic examinations. Lens opacity was assessed after pupil dilation using the modified Lens Opacities Classification System III (LOCS III). The main indices for prevalence of cataract were any lens changes, defined as the presence of a gradable cataract in one or both eyes, and all lens changes, defined as any lens changes plus a history of cataract surgery.

RESULTS

A total of 1434 participants were included in this analysis; 305 of which met the criteria for all lens changes resulting in an adjusted prevalence of 22.7% (CI95%: 20.2%-25.3%). The prevalence was 21.2% among men and 24.5% among women. The prevalence of any lens changes was 19.1% (CI95%: 16.6%-21.6%) and the prevalence was higher in women. The prevalence for both indices increased with age. Considering their better eyes, 39 people (2.7%) were shown to have low vision because of cataract and another 12 (0.8%) were classified as blind.

CONCLUSIONS

Cataract has affected approximately one-fifth of the Tehran population aged 40 years and over, women more than men, and has severely affected the vision of approximately 3.5% of this population. We found that access to cataract surgery facilities was not an issue.

The distribution of anterior chamber depth in a Tehran population: the Tehran eye study

PURPOSE

To determine the normal range of anterior chamber depth (ACD) in the population of Tehran by age and gender.

MATERIALS AND METHODS

Four hundred and ten people (800 eyes) aged 14 years and over, residing in the first four municipality areas of Tehran were selected through a stratified random cluster sampling method. The measurements were all taken by a single skilled technician using Orbscan II, between 9:00 am and 7:00 pm. The ACD was defined as the distance between the corneal endothelium and the anterior lens surface. Considering the high correlation between the ACD readings of contralateral eyes (r = 0.82, p < 0.001), only data from right eyes were analysed.

RESULTS

In the participants, the mean age was 40.6 +/- 16.8 years and 38.8% were male. The mean ACD was 2.79 mm [95% confidence interval (CI): 2.75-2.83]; 2.84 mm (95% CI: 2.79-2.90) in men and 2.75 mm (95% CI: 2.70-2.81) in women. Linear regression analysis revealed a mean ACD reduction of 0.013 mm per year of age (p < 0.001). The ACD decreased by 0.056 mm per diopter of spherical equivalent and 0.018 mm per mmHg of IOP (p < 0.001 and p = 0.030, respectively).

CONCLUSIONS

We found the normal range of ACD in the population of Tehran which is slightly different from that reported from other geographical regions. The study also demonstrated the correlation of ACD with other factors; it decreases with age, and is slightly higher in men.

Prevalence of retinal diseases and their pattern in Tehran: the Tehran eye study

PURPOSE

To determine the prevalence of retinal diseases and their pattern in Tehran through a population-based study.

METHODS

In 2002, through a stratified random cluster sampling, 6497 citizens representing a cross-section of the population of Tehran were selected from 160 clusters. Eligible people were recruited through a door-to-door household survey in selected clusters and transferred to a clinic for an extensive eye examination and interview.

RESULTS

The prevalence of retinal diseases was 8.56 per 100 (95% CI, 7.74-9.39). Acquired retinopathies (3.33 per 100) and peripheral retinal lesions (3.29 per 100) were the most common retinal diseases in our population. Cataract (12.47 per 100) was the major ocular comorbidity; high blood pressure (21.14 per 100) and diabetes mellitus (15.99 per 100) were the main systemic comorbidities among 415 patients with retinal diseases. The prevalence of low vision on the basis of best-corrected and presenting visual acuity was 0.63 and 2.87 per 100 in 415 patients with retinal disease. Two patients (0.48 per 100) were blind with corrected and presenting visual acuity. The prevalence of diabetic retinopathy in the studied population was 0.61 per 100 (95% CI, 0.39-0.82) and age-related macular degeneration was detected in 1.95 per 100 (95% CI, 1.55-2.34) of the population.

CONCLUSIONS

These findings reveal a considerable prevalence of retinal diseases in the population. The prevalence might be underestimated due to the lack of fundus photography. The findings could be considered for case finding and planning treatment programs for specific retinal diseases.

Familial aggregation of myopia in the Tehran eye study: estimation of the sibling and parent offspring recurrence risk ratios

AIM

To determine the potential influence of genetic factors on the prevalence of myopia in Tehran.

METHODS

Of 6497 citizens of Tehran sampled from 160 clusters using stratified random cluster sampling, 4565 (70.3%) participated in the study and were referred to a clinic for an extensive eye examination and interview. These were from 1259 nuclear families with the average size of 3.6. Refraction data obtained from 3321 participants aged 16 years and over are presented. Three definitions of myopia, as the spherical equivalent of -0.5, -1, and -2 diopters or less, were used. Familial aggregation of myopia was evaluated with odds ratios and recurrence risk ratios (lambda(R)) using a multiple logistic regression with generalised estimating equations (GEE), adjusted for age, sex, height, and education.

RESULTS

Multivariate analyses showed a strong familial aggregation of myopia among siblings (lambda(R) ranging from 2.09 to 3.86) and parent-offspring pairs (lambda(R) from 1.82 to 3.81) adjusted for age, sex, height, and education. The aggregation increased with higher myopia thresholds and with the use of cycloplegic refraction. The odds ratios for spouse pairs were not significantly different from 1.0. The association of myopia with sex, height, and education (and not age) remained significant in the final GEE2 model.

CONCLUSIONS

The findings indicate a relatively high degree of familial aggregation of myopia in the Tehran population, independent of age, sex, height, and education. This residual aggregation may be a result of heredity or of an unmeasured common environmental effect.

The prevalence of refractive errors among schoolchildren in Dezful, Iran

AIM

To determine the prevalence of refractive errors among schoolchildren in urban and rural areas of Dezful County, Iran.

METHODS

In a cross-sectional study, using random cluster sampling, 5721 Dezful schoolchildren were selected from 39 clusters. The participants in the study totalled 5544; 3673 elementary and middle school students and 1871 high school students. For the former group, cycloplegic refraction and for the latter, non-cycloplegic refraction was tested. In all participants, uncorrected visual acuity and best corrected visual acuity were determined, and those with a visual acuity of 20/40 or worse, underwent a complete ophthalmic examination to determine the cause of visual impairment. A spherical equivalent of -0.5 diopter (D) or worse was defined as myopia, +2.0 D or more was defined as hyperopia, and a cylinder refraction greater than 0.75 D was considered astigmatism.

RESULTS

The uncorrected visual acuity was 20/40 or worse in the better eye of 224 schoolchildren (3.8% of participants). This figure (percentage) was 14 (0.03%) based on their best corrected visual acuity and 96 (1.7%) with their presenting vision. According to results of cycloplegic refraction, 3.4% (95% confidence interval (CI), 2.5 to 4.4) of the primary and middle school students were myopic and 16.6% (95% CI, 13.6 to 19.7) were hyperopic. For high school students, these rates were 2.1% (95% CI, 0.7 to 3.5) and 33.0% (95% CI, 24.9 to 41.1), respectively, with non-cycloplegic refraction. In the multivariate logistic regression for primary and middle school students, myopia was correlated with age (p = 0.030), and hyperopia was correlated with age (p<0.001) and area of residence (p = 0.007). In high school students, hyperopia again showed a correlation with their area of residence (p = 0.029).

CONCLUSION

The present study reveals the considerable prevalence rates of refractive errors among schoolchildren in Dezful County and the high rate of an unmet need for their correction. Although myopia is not very prevalent, the high rate of hyperopia in the studied population emphasises its need for attention.

Uncorrected refractive errors and spectacle utilisation rate in Tehran: the unmet need

AIM

To determine the prevalence of the met and unmet need for spectacles and their associated factors in the population of Tehran.

METHODS

6497 Tehran citizens were enrolled through random cluster sampling and were invited to a clinic for an interview and ophthalmic examination. 4354 (70.3%) participated in the survey, and refraction measurement results of 4353 people aged 5 years and over are presented. The unmet need for spectacles was defined as the proportion of people who did not use spectacles despite a correctable visual acuity of worse than 20/40 in the better eye.

RESULTS

The need for spectacles in the studied population, standardised for age and sex, was 14.1% (95% confidence interval (CI), 12.8% to 15.4%). This need was met with appropriate spectacles in 416 people (9.3% of the total sample), while it was unmet in 230 people, representing 4.8% of the total sample population (95% CI, 4.1% to 5.4%). The spectacle coverage rate (met need/(met need + unmet need)) was 66.0%. Multivariate logistic regression showed that variables of age, education, and type of refractive error were associated with lack of spectacle correction. There was an increase in the unmet need with older age, lesser education, and myopia.

CONCLUSION

This survey determined the met and unmet need for spectacles in a Tehran population. It also identified high risk groups with uncorrected refractive errors to guide intervention programmes for the society. While the study showed the unmet need for spectacles and its determinants, more extensive studies towards the causes of unmet need are recommended.

Eye care utilization patterns in Tehran population: a population based cross-sectional study

Background

The aim of this study is to determine eye care visits which are an indicator of eye care service utilization by Tehran population and its determinants.

Methods

Through a population-based, cross-sectional study, 6497 Tehran citizens were sampled. All participants had complete eye examinations and an interview regarding demographic and socioeconomic status variables, past medical and eye history, and their previous and last eye care visits.

Results

Among those sampled, 4565 people participated in the study (response rate of 70.3%). Among these participants, 34.7 % had never visited an ophthalmologist or optometrist (95% confidence interval [CI]: 32.4 to 36.9) and 43.2% had not seen an eye care provider in the last 5 years. Multivariate logistic regression revealed that men (OR = 1.30), younger participants (each year increase in age: OR = 0.98) and the less educated (each year increase in education: OR = 0.93) were more likely, and the visually impaired were less likely (OR = 0.41) to have neglected eye care.

Conclusion

A large proportion of the population, including those in the high risk group who require eye care, has never utilized any eye care service. These data suggest that efforts have to be made to better understand the causes and to optimize the utilization of the available eye care services in the population.

Distribution of intraocular pressure in healthy Iranian individuals: the Tehran Eye Study

AIM

To provide data on the distribution of intraocular pressure (IOP) in an Iranian population.

METHODS

Through a population based, cross sectional study, 4565 Tehran citizens were studied in the Tehran Eye Study. The findings from the participants (n = 3834) aged 10 years and older free of glaucoma diagnosis or suspicion who had undergone applanation tonometry examination are presented. All participants received a standardised protocol including applanation tonometry, fundus examination, demographic data, and an interview. IOP measurement was used to evaluate its distribution by age, sex, and some eye parameters.

RESULTS

Mean (SD) IOP was 14.5 (2.6) mm Hg in the total population, 14.4 (2.7) in men, and 14.5 (2.5) in women. Mean (SD) IOP in people > or =40 years was 15.1 (2.9) mm Hg. IOP increased significantly with age and cup:disc ratio except for a fall in old age. This relation was also observed when individuals without diabetes or hypertension history were analysed. IOP increased with darker eye pigmentation except for blue/grey eyes. There was a non-linear increase in IOP from emmetropic to high myopic eyes.

CONCLUSION

Age, iris colour, and cup:disc ratio were related to IOP but not to sex. The distribution of IOP in this study was different from various other studies in different geographical regions and it seems advisable to employ a geographical approach to normal IOP interpretation.

The prevalence and causes of visual impairment in Tehran: the Tehran Eye Study

AIMS

To determine the prevalence and causes of visual impairment in Tehran, Iran, through a population based study.

METHODS

In a population based, cross sectional study, 6497 Tehran citizens were sampled from 160 clusters using a stratified, random, cluster sampling strategy. The eligible people were enumerated through a door to door household survey in the selected clusters and were invited. All participants were transferred to a clinic for an extensive eye examination and interview. Visual impairment was determined using presenting and best corrected visual acuity (low vision: visual acuity of less than 6/18 to 3/60 in the better eye; blindness: visual acuity of less than 3/60 in the better eye).

RESULTS

Of those sampled, 4565 (70.3%) people participated in the study. The age and sex standardised prevalences of visual impairment on the basis of best corrected and presenting visual acuity were 1.39% (95% confidence interval (CI), 1.07 to 1.71) and 2.52% (95% CI, 2.07 to 2.97), respectively. 15 people (0.28%; 95% CI, 0.14 to 0.42) were blind with corrected vision while 22 (0.39%; 95% CI, 0.23 to 0.56) were blind with presenting vision. Using the corrected and presenting vision, the prevalence of low visual impairment was 1.11% (95% CI, 0.84 to 1.39) and 2.13% (95% CI, 1.71 to 2.55), respectively. The causes of visual impairment according to the best corrected vision were cataract (36.0%), macular degeneration (20.0%), and amblyopia (10.7%). However, according to the presenting vision, uncorrected refractive errors were the most frequent primary cause (33.6%) and cataract (25.4%), macular degeneration (12.7%), and amblyopia (8.2%) were the other main causes of visual impairment in the study sample. The prevalence of visual impairment was associated with advancing age and lower education.

CONCLUSION

The results indicate that the burden of visual impairment is important and, although easily preventable, uncorrected refractive errors and cataract have a major role as causes of visual impairment in this population. Results also highlight the need for visual impairment prevention programmes, with emphasis on treatment of refractive errors and cataract.