Cohort profile: Shahroud Eye Cohort Study

Artificial intelligence and the scientific method: How to cope with a complete oxymoron

Artificial intelligence (AI) can be a powerful tool for data analysis, but it can also mislead investigators, due in part to a fundamental difference between classic data analysis and data analysis using AI. A more or less limited data set is analyzed in classic data analysis, and a hypothesis is generated. That hypothesis is then tested using a separate data set, and the data are examined again. The premise is either accepted or rejected with a value p, indicating that any difference observed is due merely to chance. By contrast, a new hypothesis is generated in AI as each datum is added to the data set. We explore this discrepancy and suggest means to overcome it.

The association of ALT to HDL-C ratio with type 2 diabetes in 50-74 years old adults: a population-based study

There is limited information about the relationship between diabetes mellitus (DM) and ALT to HDL-C ratio. This study aims to investigate this relationship for the first time in Iran. The data of this study were taken from the third phase of the Shahroud Eye Cohort Study, which was conducted in 2019 with the participation of 4394 people aged 50-74. ALT and HDL-C levels were measured using a BT-1500 autoanalyzer. The mean ALT/HDL-C ratio was reported along with 95% confidence intervals (CI). The multiple logistic regression was used to examine the association between this ratio and DM, while controlling for the effects of other independent variables. The mean and standard deviation of the ALT/HDL-C ratio in all participants were 16.62 ± 11.22 (95% CI 16.28-16.96). The prevalence of DM was 34.7% and individuals with DM had a mean ALT/HDL-C ratio that was 1.80 units higher than those without diabetes (P < 0.001). Also, in individuals with DM, the HDL-C was found to be 0.035 (mmol/L) lower (P < 0.001), while ALT was 1.13 (IU/L) higher (P < 0.001) compared to those without diabetes. Additionally, after controlling for confounding factors, the odds of developing DM increased in a non-linear manner with an increase in the ALT/HDL-C ratio. Abdominal obesity, advanced age, female gender, and hypertension were also found to be associated with increased odds of DM. In conclusion, an increase in the ALT/ HDL-C ratiowas associated with higher odds of DM. This ratio can serve as an important predictor for diabetes mellitus.

Finding Ophthalmic Risk and Evaluating the Value of Eye exams and their predictive Reliability (FOREVER)-A cohort study in a Danish high street optician setting: Design and methodology

PURPOSE

The purpose of the study was to describe the rationale and design of Project FOREVER (Finding Ophthalmic Risk and Evaluating the Value of Eye exams and their predictive Reliability).

DESIGN

Project FOREVER will build a comprehensive database of clinical eye and vision data collected from ~280 000 adults at 100 optician stores across Denmark. The FOREVER database (FOREVERdb) includes detailed data from refraction, visual acuity, intraocular pressure, corneal thickness, visual field assessments and retinal fundus images. Linkage to the comprehensive Danish national registries with, that is diagnostic and prescribing data permits investigation of rare associations and risk factors. 30 000 individuals over 50 also provide a saliva sample for later genetic studies and blood pressure measurements. Of these 30 000, 10 000 will also get optical coherence tomography (OCT) nerve and retinal scans. This subpopulation data is reviewed by ophthalmologists for disease detection. All participants will be asked to complete a questionnaire assessing lifestyle, self-perceived eye health and general health. Enrolment of participants began in April 2022.

PERSPECTIVE

The FOREVERdb is a powerful tool to answer a wide range of research questions that can pave the way for better eye health. This database will provide valuable insights for future studies investigating the correlations between eye and general health in a Danish population cohort, enabling research to identify potential risk factors for a range of diseases.

Vitamin D deficiency and diabetic retinopathy risk

PURPOSE

Vitamin D deficiency may play an important role in the development and progression of diabetic retinopathy. The present study aimed to assess the relationship between vitamin D deficiency and the likelihood of diabetic retinopathy.

METHODS

This nested case-control study was conducted on all type II diabetic patients among the participants of the third phase of the Shahroud eye cohort study. Overall, 278 patients aged 50 to 74 years, 101 in the case group (diabetic retinopathy) and 178 in the control group (diabetic without retinopathy), were assessed. Serum levels of vitamin D on admission were measured for all participants by a radio immunoassay (RIA) technique.

RESULTS

The overall prevalence of vitamin D deficiency (defined as a vitamin D level of less than or equal to 20mg/dL) was 30.7%. Comparison of the serum level of vitamin D across the three groups - without retinopathy, with non-proliferative retinopathy, and with proliferative retinopathy - showed a significantly lower level of this marker in the latter group (P=0.036). Reducing vitamin D to less than or equal to 20ng/mL increased the odds of proliferative retinopathy by 6.25 times (P value: 0.027).

CONCLUSION

Vitamin D deficiency is a potential risk factor for diabetes-related proliferative retinopathy.

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.

Prevalence of uncontrolled hypertension and its associated factors in 50-74 years old Iranian adults: a population-based study

BACKGROUND

By the lengthening of life span, the incidence of chronic diseases such as hypertension and uncontrolled hypertension has increased. This study aims to determine the prevalence of uncontrolled hypertension and its related factors in the age group of 50-74 years in Shahroud, northeast Iran.

METHODS

The data of the third phase of the Shahroud Eye Cohort Study were used in this study. This phase of the cohort study included 4394 participants aged 50 to 74 years from the previous phases. In addition to ophthalmological and optometric examinations, demographic characteristics, blood biochemistry tests, and blood pressure measurements were performed in this phase. Individuals with a blood pressure ≥ 140/90 mm/Hg (being treated or not treated with antihypertensive medicines) were defined as uncontrolled hypertension. In patients with diabetes and chronic kidney disease, blood pressure equal to or higher than 130/80 mm/Hg was considered uncontrolled hypertension. Descriptive statistics and multiple logistic regression were used to analyze the data.

FINDINGS

Overall, the prevalence of uncontrolled hypertension out of all the participants was 61.7% (95% CI: 60.3-63.2). Multiple regression results showed that the male gender (OR: 2.1, 95% CI: 1.5-2.9), patients with diabetes (OR:3.2, 95% CI: 2.4-4.3), and patients with chronic kidney disease (CKD) (OR: 3.2, 95% CI: 2.5-4.1) increased the risk of uncontrolled hypertension while in patients with cardiovascular disease (OR: 0.6, 95% CI: 0.4-0.8) and polypharmacy (OR: 0.2, 95% CI: 0.1-0.2) reduced the risk of uncontrolled hypertension.

CONCLUSION

The present study showed that uncontrolled hypertension has a high prevalence, and factors such as male gender, diabetes, and CKD are associated with this disorder. So, it is recommended to take the necessary measures to formulate and implement immediate actions to prevent or control hypertension.

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.

Association between Refractive Errors and Ocular Biometry in an Elderly Population

SIGNIFICANCE

The anterior chamber depth in hyperopic eyes is significantly deeper than that in myopic eyes, and this finding is independent of the axial length.

PURPOSE

This study aimed to determine the relationship between and refractive errors and ocular biometric components in a geriatric population 60 years and older.

METHODS

The present population-based cross-sectional study was performed using a multistage random cluster sampling method in Tehran, Iran. After selecting the samples, visual acuity measurement, autorefraction, subjective refraction, and slit-lamp examination were performed for all participants. Ocular biometric indices were measured with Pentacam AXL (Oculus, Wetzlar, Germany).

RESULTS

The correlation coefficients of spherical equivalent with axial length, corneal radius of curvature, axial length/corneal radius of curvature ratio, and anterior chamber depth were -0.40, 0.14, -0.63, and -0.18, respectively, after controlling the effects of age, sex, and nuclear cataract. The axial length (24.84 vs. 21.21 mm), the anterior chamber depth (2.74 vs. 2.34 mm), the ratio of the axial length to the corneal radius of curvature (3.35 vs. 2.71), and the anterior chamber volume (138.59 and 105.54 mm 3 ) were the highest and lowest in myopic and hyperopic individuals, respectively (all P < .001). In the first model, axial length and nuclear cataract were significantly inversely related to the spherical equivalent. However, corneal radius of curvature, anterior chamber depth, central corneal thickness, and corneal diameter had a significant direct relationship with the spherical equivalent. In the second model, the axial length/corneal radius of curvature ratio and cataract showed an inverse relationship with the spherical equivalent, whereas anterior chamber depth and corneal diameter had a direct relationship with the spherical equivalent.

CONCLUSIONS

Among the biometric components, the axial length/corneal radius of curvature ratio has the strongest relationship with refractive errors. The anterior chamber depth is lower in myopes compared with hyperopes after controlling the effect of axial length.

Isolated systolic hypertension and its associated risk factors in Iranian middle age and older population: a population-based study

Background

Isolated systolic hypertension (ISH), is the most common form of hypertension in older adults. However, the ISH prevalence is not well known in many developing countries such as Iran. This study was conducted to determine the ISH prevalence and its related risk factors in an Iranian population.

Methods

Data were obtained from the second phase of the Shahroud eye cohort study (ShECS) in 2014. ShECS is a longitudinal population-based study which the first phase had been conducted in 2009 using the stratified multistage cluster sampling design on 5190 people aged 40 to 70 years. The ISH prevalence was determined based on the eighth Joint National Commission guidelines for different demographic variables. The associated risk factors were estimated by multiple logistic regression and a two-tailed p-value less than 0.05 was considered significant.

Results

The ISH prevalence was 15.89% (95% CI: 14.88–16.96). It was 15.68% (14.12–17.39) and 15.87% (14.54–17.29) for men and women, respectively. The prevalence of ISH increased significantly with increasing age. The 65–70 compared to 45–69 year age group (OR = 4.21), body mass index (OR = 1.03), diabetes (OR = 1.64), retirement, compared to practitioner job (OR = 1.53), and waist to hip ratio (WHR) (OR = 9.81) were significantly associated with ISH prevalence.

Conclusions

ISH is highly prevalent among the older adult population in Iran. Given the risk of cardiovascular disease associated with ISH, it is recommended to conduct education and public health interventions to improve the detection, prevention, and treatment of ISH.

Visual functions and disability in Iranian adults: a population-based study

Background

Vision-related quality of life is related to severity of visual impairments and show the impact of eye diseases on daily activities. This study aims to assess visual functions and disability and its association with age, gender, education, marital status, and economic status in adults aged 45–69 years.

Methods

Data in this population-based study were from the second phase of the Shahroud eye cohort study and collected by using a Short-Form Visual Functioning Scale. The scores of visual function and disability were calculated based on Rasch-transformed scores of the National Eye Institute visual functioning questionnaire, where a more negative score indicates a better situation. Multiple linear regression was used to investigate the factors associated with visual functions.

Results

Among 4737 participants the visual function data for 4715 people were analyzed. The visual function of 75.3, 17.1 and 7.5% of participants were “ideal and good”, “moderate”, and “bad and very bad”, respectively, while 0.06% were unable for vision. The running mean of the visual function was calculated to be − 3.95 ± 0.02. The visual performance was worse in females than the males (β = 0.14, p = 0.005). Visual function improved with increasing levels of education (β = − 1.06, p < 0.001). It was worse in low-economic (β = 0.016, p = 0.005) and moderate-economic (β = 0.28, p < 0.001) participants than high-economic ones.

Conclusion

The visual function of Iranian adults aged 45–69 years was moderate. The male gender, higher education and the higher economic status had a better visual function.

Interocular Symmetry Analysis of Corneal Elevation Using the Fellow Eye as the Reference Surface and Machine Learning

Unilateral corneal indices and topography maps are routinely used in practice, however, although there is consensus that fellow-eye asymmetry can be clinically significant, symmetry studies are limited to local curvature and single-point thickness or elevation measures. To improve our current practices, there is a need to devise algorithms for generating symmetry colormaps, study and categorize their patterns, and develop reference ranges for new global discriminative indices for identifying abnormal corneas. In this work, we test the feasibility of using the fellow eye as the reference surface for studying elevation symmetry throughout the entire corneal surface using 9230 raw Pentacam files from a population-based cohort of 4613 middle-aged adults. The 140 × 140 matrix of anterior elevation data in these files were handled with Python to subtract matrices, create color-coded maps, and engineer features for machine learning. The most common pattern was a monochrome circle (“flat”) denoting excellent mirror symmetry. Other discernible patterns were named “tilt”, “cone”, and “four-leaf”. Clustering was done with different combinations of features and various algorithms using Waikato Environment for Knowledge Analysis (WEKA). Our proposed approach can identify cases that may appear normal in each eye individually but need further testing. This work will be enhanced by including data of posterior elevation, thickness, and common diagnostic indices.

Development of glaucoma predictive model and risk factors assessment based on supervised models

Objectives

To develop and to propose a machine learning model for predicting glaucoma and identifying its risk factors.

Method

Data analysis pipeline is designed for this study based on Cross-Industry Standard Process for Data Mining (CRISP-DM) methodology. The main steps of the pipeline include data sampling, preprocessing, classification and evaluation and validation. Data sampling for providing the training dataset was performed with balanced sampling based on over-sampling and under-sampling methods. Data preprocessing steps were missing value imputation and normalization. For classification step, several machine learning models were designed for predicting glaucoma including Decision Trees (DTs), K-Nearest Neighbors (K-NN), Support Vector Machines (SVM), Random Forests (RFs), Extra Trees (ETs) and Bagging Ensemble methods. Moreover, in the classification step, a novel stacking ensemble model is designed and proposed using the superior classifiers.

Results

The data were from Shahroud Eye Cohort Study including demographic and ophthalmology data for 5190 participants aged 40-64 living in Shahroud, northeast Iran. The main variables considered in this dataset were 67 demographics, ophthalmologic, optometric, perimetry, and biometry features for 4561 people, including 4474 non-glaucoma participants and 87 glaucoma patients. Experimental results show that DTs and RFs trained based on under-sampling of the training dataset have superior performance for predicting glaucoma than the compared single classifiers and bagging ensemble methods with the average accuracy of 87.61 and 88.87, the sensitivity of 73.80 and 72.35, specificity of 87.88 and 89.10 and area under the curve (AUC) of 91.04 and 94.53, respectively. The proposed stacking ensemble has an average accuracy of 83.56, a sensitivity of 82.21, a specificity of 81.32, and an AUC of 88.54.

Conclusions

In this study, a machine learning model is proposed and developed to predict glaucoma disease among persons aged 40-64. Top predictors in this study considered features for discriminating and predicting non-glaucoma persons from glaucoma patients include the number of the visual field detect on perimetry, vertical cup to disk ratio, white to white diameter, systolic blood pressure, pupil barycenter on Y coordinate, age, and axial length.

Associated factors and distribution of posterior corneal astigmatism in a middle-aged population

CLINICAL RELEVANCE

Posterior corneal astigmatism has an important role in diagnosis and treatment of astigmatism, but it is usually overlooked.

BACKGROUND

This cross-sectional study aimed to investigate the distribution of posterior corneal astigmatism (PCA) and its associated factors in a middle-aged population that participated in the Shahroud Eye Cohort Study (ShECS) phase II.

METHODS

Anterior corneal astigmatism (ACA) and PCA values were measured using rotating Scheimpflug System (Pentacam HR, Oculus). With-the-rule (WTR) astigmatism was considered when the steepest corneal meridian was aligned within 90° ± 30°, and against-the-rule (ATR) astigmatism when the steepest meridian was 0 ± 30°. All the remaining values were considered as oblique astigmatism. Logistic regression models were used for evaluating the association of PCA magnitudes with other factors.

RESULTS

The current study consisted of 3871 eyes with available Pentacam data. Mean age of participants was 55.4 ± 6.1 years and 1557 (40.2%) subjects were male. Means of ACA and PCA were 0.77 ± 0.67 and -0.24 ± 0.15 D, respectively. The majority of PCA consisted of WTR astigmatism (82.43%), while ACA mostly showed ATR astigmatism (55.46%). PCA > 0.3 D was associated with male sex (OR = 1.16, P-value = 0.028) and spherical equivalent (OR = 0.93, P-value = 0.011) in the adjusted model, while PCA > 0.5 dioptre was strongly associated with myopia (OR = 4.6, P-value < 0.001).

CONCLUSION

The most common forms of ACA and PCA in middle-aged Iranian adults were ATR and WTR, respectively. While the shape of posterior corneal surface remained mostly unchanged across ages of 45 to 69 years, ACA was associated with a decrease in ATR proportion. Moreover, the most significant factors associated with higher magnitudes of PCA were male sex and myopia.

Components of Pittsburgh Sleep Quality Index in Iranian adult population: an item response theory model

Objective/background

There have been conducted few studies in Iran on the quality of sleep in the general population. This study aimed to use the item response theory (IRT) model to examine the accuracy of the seven components of the Pittsburgh Sleep Quality Index (PSQI) and to provide an appropriate cut-off point for population-based studies.

Methods

This study was performed using the data of the second phase of the Shahroud Eye Cohort Study (ShECS) in 2014. The sleep quality of 4710 participants was measured through PSQI. Using an IRT model, the seven components of the index are considered as indicators and sleep quality as the latent variable in the measurement model. This model supposed that there is only one hidden component to explain the respondent's behavior to a number of items.

Results

Results of analyzing different components of PSQI showed that component 6 (using sleep medication) and 7 (daytime dysfunction disorder) had the lowest values of discrimination parameter and component 4 (habitual sleep efficiency) and 1 (sleep quality) had the highest value of discrimination parameter. Persons with an expected sleep quality score of less than or equal to 6.5 will be defined as good sleep quality pattern.

Conclusions

Since discrimination values for components 6 and 7 are less than the values for other components, the use of the standardized latent scores is emphasized for assessing the quality of sleep in the population.

•

For seven components of PSQI, difficulty and discrimination parameters were estimated using IRT.

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Using an IRT model persons with an expected sleep quality score ≤ 6.5 will be defined as good sleep quality pattern.

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Almost 42.9% and 0.2% had poor and very poor sleep quality.

•

Sleep quality, and habitual sleep efficiency components had the highest value of discrimination parameter.

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Component 6 and 7 play the lowest role in assessing sleep quality in the general population.

Prospective cohort study on the social determinants of health: Tehran University of Medical Sciences employees` cohort (TEC) study protocol

Background

In this study, the association between the social determinants of health (SDH) as well as other health risk factors and outcomes will be evaluated at different socioeconomic layers.

Methods/design

This is a prospective cohort study that was launched in January 2018 on Tehran University of Medical Sciences’ employees. The initial enrolment phase will continue up to March 2021, or until a sample size of 5500 is reached. In addition to annual phone-calls, the participants will be followed thrice at 5-year intervals. Data are collected through blood and urine samples, complete physical examination, anthropometric evaluation, and the completion of questionnaires related to SDH, such as socioeconomic status and social capital, history of diseases, lifestyle (including, nutrition, physical activity, cigarette and hookah smoking), occupational exposures (including psychosocial factors at work and work-family conflicts), and different aspects of physical, mental and occupational health as health outcomes. The association between independent variables and health (objective or subjective) are examined using multiple models and by controlling the confounding effects. Moreover, the trend in lifestyle changes and its impact on health are evaluated.

Discussion

Our study will explore the key social determinants as well as other factors including socioeconomic status and social capital, history of diseases, lifestyle and occupational exposures that affect health. This will provide social and occupational health decision-makers and stakeholders with new and valuable evidence in an era in which we are witnessing huge changes in lifestyle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-020-09798-9.

The Distribution of Vertical Cup-to-Disc Ratio and its Determinants in the Iranian Adult Population

Purpose:

To determine the distribution of vertical cup-to-disc ratio (VCDR) and its relationship with ocular biometric indices.

Methods:

This study was conducted in 4737 individuals aged 45-69 years living in Shahroud who participated in the second phase of Shahroud Eye Cohort Study in 2014. All participants underwent eye examinations including the measurement of visual acuity and refraction, slit-lamp biomicroscopy, retinal examination, and fundoscopy. Normality index was used to describe data distribution, and a multiple beta regression, with adjustment for the effect of cluster sampling, was applied to explore the relationship between VCDR and the study variables.

Results:

The mean [95% confidence interval (CI)] VCDR was 0.297 (0.293-0.301) in all participants; 0.296 (0.291-0.302) in men and 0.297 (0.292-0.302) in women. The highest mean VCDR was seen in the age group 55-59 years (0.299, 95% CI: 0.292-0.307). The 97.5^th percentile was 0.600. According to multiple beta regression analysis, VCDR had a positive association with the female sex (P = 0.028), spherical equivalent (P < 0.001), cigarette smoking (P = 0.020), and axial length (P < 0.001), and had a negative association with hypertension (P = 0.001), best corrected visual acuity (P < 0.001), hyperlipidemia (P = 0.029) and anterior chamber depth (P = 0.001).

Conclusions:

The mean VCDR and the 97.5^th percentile were lower than most other studies. Although ethnicity and race may play a role in this difference, this difference should be considered in clinical decisions in the current population.

Comparison of the accuracy of three diagnostic criteria and estimating the prevalence of metabolic syndrome: A latent class analysis

Background:

Metabolic syndrome (MetS) is a growing public health problem with a worldwide distribution, and its prevalence is rapidly increasing worldwide. Hence, this study aimed to compare the prevalence of MetS based on the International Diabetes Federation (IDF), the National Cholesterol Education Program Expert Panel Adult Treatment Panel III (NCEP ATP III), and the American Association of Clinical Endocrinologists (AACE) diagnostic criteria.

Materials and Methods:

In this cross-sectional study, a total of 4737 people aged 45–69 years were enrolled in the 2^nd phase of Shahroud Eye Cohort Study. We evaluated the prevalence of MetS with 95% confidence intervals by age and sex groups and according to MetS components. The accuracy (sensitivity and specificity) of these three methods was compared using latent class analysis. Finally, kappa statistic was used to determine the agreement between the diagnostic methods.

Results:

The prevalence of MetS varied from a minimum of 47.2% (as defined by the AACE) to a maximum of 60.0% (as defined by the IDF). The sensitivity of the three diagnostic methods of IDF, NCEP ATP III, and AACE was 98.9%, 94.4%, and 91.1%, respectively, and the specificity of these three methods was 94.6%, 97.0%, and 98.4%, respectively. Moreover, the highest agreement was found between the definition of the IDF and the NCEP ATP III.

Conclusion:

The IDF diagnostic method has a higher sensitivity for the diagnosis of MetS in Iranian middle-aged people. It is recommended to use this method for identifying more people at risk of MetS.

Keratoconus after 40 years of age: a longitudinal comparative population-based study

PURPOSE

To determine 5-year changes in keratoconus indices and corrected distance visual acuity in 40-64-year-old keratoconus compared with normal subjects.

METHODS

In this prospective population-based cohort study, 5-year changes in Belin grading system indices including the average radii of curvature in the 3 mm zone surrounding the thinnest point in the anterior (ARC-3 mm) and posterior (PRC-3 mm) cornea, corrected distance visual acuity, minimum corneal thickness, maximum Ambrosio's relational thickness (ART-max), and maximum anterior keratometry indices centered on steepest point in the central 3 mm (Kmax-3 mm), 4 mm (Kmax-4 mm), and 5 mm (Kmax-5 mm) zones were compared between keratoconus and normal participants. In the analysis, comparisons were made between all keratoconus eyes and the right eyes of normal participants.

RESULTS

The mean age in the keratoconus (n = 16 eyes) and normal (n = 1986 eyes) groups (48.31 ± 4.78, 49.37 ± 5.79 years, respectively) was not statistically different (P = 0.327). The two groups differed in terms of changes in PRC-3 mm (- 0.07 ± 0.15 vs. + 0.001 ± 0.14 mm, respectively, P = 0.042) and ART-max (- 6.28 ± 25.19 vs. + 15.8 ± 72.7 μm, respectively, P = 0.003). There were significant correlations between the reduction in PRC-3 mm and its baseline value (β = - 0.20, P < 0.001) and keratoconus (β = - 0.26, P < 0.001). The reduction in ART-max significantly correlated with its baseline value (β = - 0.43, P < 0.001) and keratoconus (β = - 111.74, P < 0.001).

CONCLUSION

According to these findings, posterior corneal steepening and thinning in keratoconus patients continue after the age of 40 years, but it is clinically negligible. The changes are independent of normal age-related changes and appear to be slower in cases with steeper and thinner corneas.

Horizontal inequity in the utilization of cataract surgery in Iran: Shahroud Eye Cohort Study, 2009-2014

Background: Since there was no evidence about economic inequity in utilization of cataract surgery in developing countries, such as Iran, this study was designed to measure horizontal inequity in the utilization of cataract surgery and its changes in an Iranian middleaged population in 2009 and 2014. Methods: Using data from the first and second phases of Shahroud Eye Cohort Study (2009-2014), the economic inequity in the utilization of cataract surgery in an Iranian middle-aged population aged 40-64 years in 2009 and 2014 was evaluated. The horizontal inequity index (HI) was determined using the indirect standardization method based on a nonlinear (probit) model and the concentration index (C) was decomposed into the contribution of each factor. The analyses were performed using STATA software version 12/SE, and significance level was set at less than 0.05. Results: The HI in the utilization of cataract surgery increased from 0.080 (95% CI: 0.011-0.098) in 2009 to 0.166 (95% CI: 0.0821- 0.228) in 2014. Decomposition of changes in the concentration index showed that among need and non-need variables, older age and economic status (being among the wealthiest 20%) were the greatest contributors, with shares of 67.5% and 57.5%%, respectively, which led to pro-rich inequity during the study periods. Conclusion: The present study demonstrated that utilization of cataract surgery did not have an equal distribution among economic quintiles, despite considering equal needs based on cataract severity. Results demonstrated that older age and economic status were the greatest contributors to HI increase in 2009 and 2014.

The reduction of horizontal inequity in unmet refractive error: The Shahroud Eye Cohort Study, 2009-2014

Purpose

To measure Horizontal Inequity Index (HI) of unmet refractive error and its changes between 2009 and 2014 in Iran.

Methods

The data used in this study was taken from population-based study, Shahroud Eye Cohort Study. The number of participants analyzed in first (2009) and second phases of study (2014) were 5190 and 4737, respectively, and individuals between 40 and 64 years were included. The HI was determined by using the Concentration Index (C) based on the nonlinear (Probit) model, and C was decomposed to identify and quantify the contribution of each factor.

Results

After adjusting for need variables, the results demonstrated that the HI in unmet refractive need decreased from −0.288 (95% CI: 0.370, −0.206) in the 2009 to −0.132 (95% CI: 0.290, −0.028) in 2014. Decomposition of the C showed that level of education and economic status were the greatest contributors with shares of 26.2% and 17.9%, respectively, in reducing the amount of HI in unmet refractive error between 2009 and 2014.

Conclusions

The current study demonstrated that unmet refractive error did not have an equal distribution among economic quintiles, despite the same need for correcting refractive errors. Reducing the amount of HI in unmet refractive error between 2009 and 2014 indicated an improvement in the unmet need in the five years period between two phases of study.

Correlation analysis and multiple regression formulas of refractive errors and ocular components

The multiple regression formulas and correlation of ocular components with refractive errors are presented by Gaussian optics. The refractive error changing rate for the cornea and lens power, the axial length, anterior chamber depth (ACD) and vitreous chamber depth (VCD) are calculated, including nonlinear terms for more accurate rate functions than the linear theory. Our theory, consistent with the empirical data, shows that the Pearson correlation coefficients for spherical equivalent (SE) and ocular components are highest for SE with axial length, ACD and VCD and weakest for corneal power, lens power and lens thickness. Moreover, our regression formulas show the asymmetric feature of the correlation that the axial length, ACD and VCD are more strongly correlated (with higher negative regression constants) with refractive errors in eyes with hyperopia than in eyes with myopia, particularly for severe hyperopia.

Transition in tobacco use stages and its related factors in a longitudinal study

OBJECTIVES

Considering the increase in the non-communicable diseases associated with tobacco use in recent decades in Iran, it is necessary to have a general view of the current condition. This study aimed to identify factors associated with tobacco use and to estimate the probability of a 5-year transition in the stages of tobacco use in an adult population.

METHODS

In this study, 5190 people in the 40-64-year-old population of Shahroud (North East of Iran) were interviewed in 2009 and 2014 on tobacco smoking. The association of independent variables with tobacco smoking was evaluated using the population-averaged logit model. We calculated smoking transition probabilities from non-smoking to current smoking and past-smoking stages during a 5-year span.

RESULTS

The prevalence of current tobacco smoking in 40-69-years age group was 11.1% (95% CI 10.3-12.0), 1% among women (95% CI 0.8-1.3) and 25.6% among men (95% CI 23.7-27.6). During this 5-year period, the probability of transition of a non-smoker to an overall current tobacco smoker was 2.3%. Meanwhile, 18.5% of the overall current tobacco smokers had changed into past smokers. Unemployed (OR = 2), male gender (OR = 53.9), widow/widowers (OR = 5.4), divorces (OR = 3.3), and high economic status (OR = 1.2) are associated to tobacco smoking.

CONCLUSIONS

Compared with the other studies, the prevalence of tobacco use in this population is low but transition rate of non-smokers into current smokers or past smokers is high. Conducting interventions on determinants of starting and quitting smoking and education and awareness raising on the risk and harms of smoking seems necessary.

Cardiovascular mortality in a Western Asian country: results from the Iran Cohort Consortium

OBJECTIVES

Cardiovascular mortality in Western Asia is high and still rising. However, most data documented on risk prediction has been derived from Western countries and few population-based cohort studies have been conducted in this region. The current study aimed to present the process of pooling data and cardiovascular disease (CVD) mortality incidences for four Iranian cohorts.

METHODS

From the Iran Cohort Consortium, the Golestan Cohort Study (GCS), Tehran Lipid and Glucose Study, Isfahan Cohort Study (ICS) and the Shahroud Eye Cohort Study (ShECS) were eligible for the current study since they had appropriate data and follow-up visits. Age-standardised CVD mortality rates were estimated for ages 40-80 and 40-65 years. Cox regression was used to compare mortalities among cohorts. Adjusted marginal rates were calculated using Poisson regression.

RESULTS

Overall, 61 291 participants (34 880 women) aged 40-80 years, free of CVD at baseline, were included. During 504 606 person-years of follow-up, 1981 CVD deaths (885 women) occurred. Age-standardised/sex-standardised premature CVD mortality rates were estimated from 133 per 100 000 person-years (95% CI 81 to 184) in ShECS to 366 (95% CI 342 to 389) in the GCS. Compared with urban women, rural women had higher CVD mortality in the GCS but not in the ICS. The GCS population had a higher risk of CVD mortality, compared with the others, adjusted for conventional CVD risk factors.

CONCLUSIONS

The incidence of CVD mortality is high with some differences between urban and rural cohorts in Iran as a Western Asian country. Pooling data facilitates the opportunity to globally evaluate risk prediction models.

Assessment of Horizontal Inequity in Eye Care Utilization in the Iranian Middle-aged Population

PURPOSE

The present study was designed to determine the extent that horizontal inequity was realized regarding eye care utilization in a middle-aged population as well as factors affecting this equity.

METHODS

Data were obtained from a population-based study (Shahroud Eye Cohort Study) in 2009 that included 5190 participants from 40 to 64 years of age. Horizontal inequity was determined based on the following variables: (i) economic status, (ii) eye care service needs, (iii) non-need variables, and (iv) eye care utilization (visiting an ophthalmologist or optometrist). Decomposition analysis of the concentration index based on a nonlinear model and indirect standardization was used to ascertain the contribution of each factor in inequity of eye care utilization.

RESULTS

After adjusting for need variables, the results of our study demonstrated that horizontal inequity in eye care utilization in a middle-aged Iranian population remained positive and significant (horizontal inequity: 0.19; 95% confidence interval: 0.17-0.23) indicating that use of services was focused among participants with a better financial situation. Furthermore, decomposition analysis demonstrated that educational level and economic status had the greatest contribution (54.1% and 41.1%, respectively) in comparison to other variables.

CONCLUSION

This study demonstrated that horizontal inequity exists in eye care utilization among the middle-aged Iranian population.

Pre-hypertension and the risk of diabetes mellitus incidence using a marginal structural model in an Iranian prospective cohort study

OBJECTIVES

The aim of this study was to evaluate the effect of pre-hypertension and its sub-classification on the development of diabetes.

METHODS

In this cohort study, 2,941 people 40 to 64 years old without hypertension or diabetes were followed from 2009 through 2014. According to the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC)-7 criteria, we classified participants into normal and pre-hypertension groups. The effect of pre-hypertension on the 5-year incidence rate of diabetes was studied using inverse probability of treatment weighting. We modeled the exposure and censored cases given confounding factors such as age, sex, body mass index, smoking, economic status, and education.

RESULTS

The 5-year incidence rate of diabetes among people with pre-hypertension and those with normal blood pressure (BP) was 12.7 and 9.7%, respectively. The risk ratio (RR) for people with pre-hypertension was estimated to be 1.13 (95% confidence interval [CI], 0.90 to 1.41). The RRs among people with normal BP and high-normal BP, according to the JNC-6 criteria, compared to those with optimal BP were 0.96 (95% CI, 0.73 to 1.25) and 1.31 (95% CI, 1.01 to 1.72), respectively.

CONCLUSIONS

Our results showed that participants who had higher levels of BP (high-normal compared to optimal BP) had a higher risk of diabetes development. With regard to the quantitative nature of BP, using the specifically distinguishing of stage 1 hypertension or high-normal BP may be a more meaningful categorization for diabetes risk assessment than the JNC-7 classification.

Prevalence and risk factors of glaucoma in an adult population from Shahroud, Iran

Purpose

To determine the prevalence of glaucoma and its risk factors in a 40- to 64-year-old Iranian population.

Methods

In this cross-sectional study, 6311 individuals between the ages of 40–64 years old in Shahroud, a northeastern city in Iran, were selected through multistage cluster sampling. All participants underwent eye exams, optometry, and imaging. They had stereoscopic optic disc photography, visual field evaluation, and their intraocular pressure (IOP) was measured by ophthalmologists before pupil dilation. Glaucoma was defined by the standardized criteria, offered by the International Society for Geographical and Epidemiological Ophthalmology (ISGEO).

Results

Of the 5190 people who participated in the study (82.2%), data from 4637 people were used in the analysis. The prevalence of glaucoma was 1.92% [95% confidence intervals (CI): 1.53–2.31]; 1.4% (95% CI: 0.96–1.84) in women and 2.62% (95% CI: 1.95–3.28) in men. Glaucoma prevalence was 0.9% in the 40–44 years age group, and significantly increased to 3.55% in the 60–64 years age group. In the multiple logistic regression model, age [odds ratio (OR) = 1.08, 95% CI: 1.05–1.12], IOP (OR = 1.04, 95% CI: 1.01–1.06), axial length (OR = 1.34, 95% CI: 1.1–1.63), corneal radius of curvature (OR = 2.76, 95% CI: 1.26–6.06), and corneal diameter (OR = 0.63, 95% CI: 0.46–0.87) showed significant statistical association with glaucoma.

Conclusions

The prevalence of glaucoma was considerably high at older ages. Major risk factors confirmed by this study included older age and high IOP. Certain ocular biometric components such as the axial length and the corneal radius of curvature must be noted as important glaucoma risk factors at younger ages.

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.

Economic Inequality in Presenting Vision in Shahroud, Iran: Two Decomposition Methods

Background: Visual acuity, like many other health-related problems, does not have an equal distribution in terms of socio-economic factors. We conducted this study to estimate and decompose economic inequality in presenting visual acuity using two methods and to compare their results in a population aged 40-64 years in Shahroud, Iran.

Methods: The data of 5188 participants in the first phase of the Shahroud Cohort Eye Study, performed in 2009, were used for this study. Our outcome variable was presenting vision acuity (PVA) that was measured using LogMAR (logarithm of the minimum angle of resolution). The living standard variable used for estimation of inequality was the economic status and was constructed by principal component analysis on home assets. Inequality indices were concentration index and the gap between low and high economic groups. We decomposed these indices by the concentration index and BlinderOaxaca decomposition approaches respectively and compared the results.

Results: The concentration index of PVA was -0.245 (95% CI: -0.278, -0.212). The PVA gap between groups with a high and low economic status was 0.0705 and was in favor of the high economic group. Education, economic status, and age were the most important contributors of inequality in both concentration index and Blinder-Oaxaca decomposition. Percent contribution of these three factors in the concentration index and Blinder-Oaxaca decomposition was 41.1% vs. 43.4%, 25.4% vs. 19.1% and 15.2% vs. 16.2%, respectively. Other factors including gender, marital status, employment status and diabetes had minor contributions.

Conclusion: This study showed that individuals with poorer visual acuity were more concentrated among people with a lower economic status. The main contributors of this inequality were similar in concentration index and Blinder-Oaxaca decomposition. So, it can be concluded that setting appropriate interventions to promote the literacy and income level in people with low economic status, formulating policies to address economic problems in the elderly, and paying more attention to their vision problems can help to alleviate economic inequality in visual acuity.

The Distribution of Macular Thickness and Its Determinants in a Healthy Population

PURPOSE

To determine the distribution of macular thickness in a healthy Iranian population aged 45-69 years and its association with certain determinants.

METHODS

All participants underwent optometric examinations including measurement of uncorrected and corrected visual acuity, objective refraction by retinoscopy, and subjective refraction. Subsequently, all participants underwent slit-lamp biomicroscopy followed by fundus examination through direct and indirect ophthalmoscopy, and optical coherence tomography (OCT) imaging under pupil dilation.

RESULTS

Mean central macular thickness was 255.4 µm (95% confidence interval, CI, 254.5-256.3 µm), average inner macular thickness was 316.5 µm (95% CI 315.9-317.1 µm), average outer macular thickness was 275.3 µm (95% CI 274.8-275.8 µm), and overall average thickness was 278.6 µm (95% CI 278.1-279.1 µm). A linear multiple regression model showed that all indexes were significantly larger in male participants (p < 0.001). Central macular thickness increased with age (coef = 0.25, p < 0.001) while overall, inner and outer macular thickness decreased with age (coef = -0.18, -0.15, -0.19, respectively, all p < 0.001). Central and inner macular thickness had a positive correlation (coef = 3.8, 2.6, respectively, both p < 0.001) and outer macular thickness had a negative correlation (coef = -1.6, p < 0.001) with axial length.

CONCLUSION

Age, sex, refractive error, axial length, and keratometry were found to be associated with macular thickness. These factors should be taken into account when interpreting macular thickness measurements with spectral-domain OCT.

Distribution of intraocular pressure and its determinants in an Iranian adult population

AIM

To determine the distribution of intraocular pressure (IOP) and its determinants in an Iranian population.

METHODS

In a cross-sectional survey, random cluster sampling was conducted from the 40-64 years old population of Shahroud, in the north of Iran. All participants had optometry and ophthalmic exams. IOP was determined using the Goldmann tonometry method and biometric components were measured.

RESULTS

Of the 6311 people selected for the study, 5190 (82.2%) participated. The mean age of the participants was 50.9±6.2y and 58.7% of them were female. Mean IOP was 12.87±2.27 mm Hg. In this study 0.3% of the participants had an IOP higher than 21 mm Hg. The multiple linear regression model revealed that sex (Coef=-0.30; 95% CI: -0.43 to -0.17), diabetes (Coef=0.43; 95% CI: 0.19 to 0.67), high systolic blood pressure (Coef=0.02; 95% CI: 0.01 to 0.02), high body mass index (BMI) (Coef=0.03; 95% CI: 0.01 to 0.04), higher education (Coef=0.02, 95% CI: 0.01 to 0.04), thicker central corneal thickness (Coef=0.01; 95% CI: 0.01 to 0.02), and myopic shift in spherical equivalent (Coef=-0.14; 95% CI: -0.18 to -0.10) significantly correlated with high IOP.

CONCLUSION

The IOP in this 40-64 years old population is low overall. In the north of Iran, average IOP is statistically significantly correlated with female sex, diabetes, higher BMI, systolic blood pressure, higher education, thicker cornea, and myopic refractive error.

High Incidence of Diabetes Mellitus Among a Middle-Aged Population in Iran: A Longitudinal Study

OBJECTIVES

There are few data concerning the incidence rates of diabetes in Iran. This study aimed to determine the incidence of diabetes and its risk factors in a middle-aged population in Iran.

METHODS

All of the people who participated in the first phase of the Shahroud eye cohort study were invited to the study in 2014; after signing informed consent forms, a total of 4737 people 45 to 69 years of age were enrolled in the second phase of the study (participation rate: 91.3%). The 5-year incidence rate of diabetes was determined by age and sex, and we used the binomial logistic regression model to calculate the risk ratio.

RESULTS

The prevalence of diabetes in the second phase was 20.19% in men, 26.45% in women and 23.89% in the total group. The 5-year incidence of diabetes was 11.19% in men, 15.55% in women and 13.73% in both sexes. With increases in age, the incidence of diabetes rose in both sexes. Age (risk ratio [RR]: 1.02; CI 95%: 1.01 to 1.03) hypertension (RR: 1.41; CI 95%: 1.15 to 1.74), being overweight (RR: 2.17; CI 95%: 1.64 to 2.88) and obesity (RR: 3.4; CI 95%: 2.53 to 4.41) were associated with increased risks for the incidence of diabetes.

CONCLUSIONS

This study is 1 of the few studies in Iran that has reported the incidence of diabetes. Because the incidence of diabetes was high in the studied population, it is necessary for the health system to design and implement emergency intervention to prevent further spread of diabetes and its complications.

Dyslipidemia and its risk factors among urban middle-aged Iranians: A population-based study

AIMS

Dyslipidemia is a known risk factor for cardiovascular disease and is a leading cause of mortality in developed and developing countries. This study was aimed to determine the prevalence of dyslipidemia and its risk factors in an urban group of Iranian adult population.

METHODS

In this study, based on the criteria set by the National Cholesterol Education Program, the prevalence of dyslipidemia was evaluated in a population of 4737 people aged 45-69 years who participated in the second phase of an ophthalmology cohort study in Shahroud. Dyslipidemia prevalence was determined by age, sex, and risk factors of the disease; the findings were tested by using simple and multiple logistic regression.

RESULTS

The prevalence of dyslipidemia was 66.5% (CI 95%: 64.4-68.6) in males, 61.3% (CI 95%: 59.5-63.2) in females, and 63.4% (CI 95%: 62.0-64.9%) in both sexes. The prevalence of hypertriglyceridemia, hypercholesterolemia, low HDL-C, and high LDL-C, respectively, was 28.8%, 13.4%, 42.3%, and 13.4%, respectively. In multivariate logistic regression model, increase of age (for females), abdominal obesity, overweight and obesity, hypertension, and diabetes were associated with an increased odd of dyslipidemia.

CONCLUSION

The prevalence of dyslipidemia in middle-aged urban population in Iran is high, and with increasing age there is an increased risk of dyslipidemia. Hence, considering the growing trend of aging in Iran, there is need for taking special measures to deal with dyslipidemia as a health priority. Furthermore, the need for planning in order to reduce the risk of dyslipidemia and prevent its complications is greater than ever.

Five year changes in central and peripheral corneal thickness: The Shahroud Eye Cohort Study

PURPOSE

To determine five year changes in corneal thickness from the apex to the 8mm periphery and related factors through a longitudinal population-based study of middle-aged Iranians.

METHODS

In the first phase, 4670 of the 5190 participants, and in the second phase, 4666 of the 4737 participants were examined with the Pentacam. In this report, analysis was done on right eye data of 2509 people who had no diabetes, pterygium, or history of eye surgery, and their image quality was displayed as "ok". Thickness changes in different parts of the cornea and their relation with age, gender, refractive error, and intraocular pressure (IOP) were assessed using repeated measures analysis of covariance.

RESULTS

Corneal thickness reduced by 1.5±11.7μm in the apex, 2.6±11.7μm in the thinnest point, and 5.3±12.2, 7.7±14.3, and 11.4±18.6μm in peripheral rings of 2, 3, and 4mm radius, respectively (all p<0.001 with and without adjusting for baseline thickness). Of the studied thickness variables, only changes in the 4mm ring significantly related with age (p<0.001) and gender (p<0.001); there was less change in older age and in men. Thickness changes were not related to refractive error or IOP (all p>0.05).

CONCLUSION

Corneal thickness decreased with age in this sample of 40-64year olds. There was significantly greater thinning in the periphery compared to the corneal center even after controlling for baseline thickness. Results of this longitudinal study can be helpful in understanding age-related changes in the cornea and the eye.

The prevalence of ptosis in an Iranian adult population

Purpose

To determine upper eyelid ptosis prevalence and some related factors in 44- to 69-year-olds of Shahroud in the north of Iran.

Methods

In 2009, using multi-stage cluster sampling, 300 clusters of 40–64-year-olds were selected in Shahroud city, and all 5190 participants were invited to be re-examined in 5 years (2014). The current report is the second phase of the study in which 4737 (91.3%) people participated and underwent vision tests, slit lamp examination, biometry, and ophthalmoscopy in 2014. Upper eyelid ptosis was determined by an ophthalmologist.

Results

The prevalence of upper eyelid ptosis was 4.7% [95% confidence interval (CI): 4.1–5.4]; 5.2% in women and in 4.0% in men. The prevalence of bilateral and unilateral ptosis was 1.3% (95% CI: 1.0–1.7) and 3.4% (95% CI: 2.8–4.0), respectively. The observed prevalence of ptosis was 3.1% in the 45- to 49-year age group and 5.8% in 65- to 69-year-olds. The prevalence of ptosis increased with age. In the multiple logistic regression model, ptosis prevalence correlated with older age, diabetes (odds ratio = 1.53, 95% CI: 1.16–2.02) and hypertension (odds ratio = 1.41, 95% CI: 1.03–2.92). Mean corneal astigmatism was 1.02 (95%C]: 0.87–1.18) diopter in ptotic eyes and 0.87 (95% CI: 0.84–0.89) diopter in non-ptotic eyes (p = 0.013).

Conclusions

The present report provides valuable information on the prevalence of ptosis in a population of 45-to 69-year-olds. The prevalence of ptosis in this study was considerably high and significantly increased with age.

The Prevalence of Exfoliation Syndrome in an Iranian Population Aged 45-69 Years

PURPOSE

To determine the prevalence of exfoliation syndrome (XFS) and some of its related factors in an Iranian population aged 45-69 years.

METHODS

In the first phase of the Shahroud Eye Cohort Study, 5190 people in 300 clusters from Shahroud city in the northeast of Iran participated in the study. The second phase of the study was conducted 5 years later in 2014. Vision testing, refraction, slit lamp examination, and fundus examination were performed for all participants. In this study, XFS was determined by an ophthalmologist using slit lamp biomicroscopy.

RESULTS

Of the 5190 first phase study participants, 4737 participated in the second phase (response rate 91.3%). In this study, the prevalence of XFS was 0.46% (95% confidence interval, CI, 0.24-0.68%) and the prevalence of bilateral XFS was 0.20% (95% CI 0.07-0.33%). XFS prevalence in men was 0.74% (95% CI 0.28-1.20%) and in women 0.26% (95% CI 0.07-0.45%). In a multivariable-adjusted logistic regression model, age, sex, diabetes, smoking status, dyslipidemia, and hypertension were entered into the model as covariables, where older age (odds ratio, OR, 1.18, 95% CI 1.08-1.28) was the only variable that remained significantly associated with XFS prevalence.

CONCLUSION

The prevalence of XFS in this study was very low. Similar to other studies, age was a factor associated with this syndrome.

Hyperopia and Lens Power in an Adult Population: The Shahroud Eye Study

Purpose:

To explore the relationship between lens power and refractive error in older adults following age-related hyperopic shifts.

Methods:

From the Shahroud Eye Cohort Study, subjects aged 55-64 years without clinically significant cataracts (with nuclear opacity of grade 0 to 1) were included to maximize the proportion of subjects with age-related hyperopic shifts that normally occur between 40 to 60 years of age, before interference from the myopic shift due to nuclear cataracts. Mean axial length (AL) values, corneal power, anterior chamber depth, lens thickness, and lens power were analyzed and compared among three refractive groups (myopes, emmetropes, and hyperopes).

Results:

A total of 1,006 subjects including 496 (49.63%) male subjects were studied. Corneal power was similar in all refractive groups. Hyperopes had + 1.69 diopters higher mean spherical equivalent refractive error and − 0.50 mm shorter AL than emmetropes. Myopes had 0.67 mm longer AL than emmetropes. Hyperopes had significantly increased lens thickness as compared to emmetropes (4.42 vs. 4.39 mm respectively). In this adult sample, the hyperopic group had lower lens power (+22.29 diopters vs. +22.54 diopters in emmetropes, P = 0.132). Myopes had similar lens power as emmetropes.

Conclusion:

Axial length is the principal determinant of refractive errors. Lens power may have importance in determining hyperopia in adults free of cataract.

Association between Refractive Errors and Ocular Biometry in Iranian Adults

Purpose:

To investigate the association between ocular biometrics such as axial length (AL), anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD) and corneal power (CP) with different refractive errors.

Methods:

In a cross-sectional study on the 40 to 64-year-old population of Shahroud, random cluster sampling was performed. Ocular biometrics were measured using the Allegro Biograph (WaveLight AG, Erlangen, Germany) for all participants. Refractive errors were determined using cycloplegic refraction.

Results:

In the first model, the strongest correlations were found between spherical equivalent with axial length and corneal power. Spherical equivalent was strongly correlated with axial length in high myopic and high hyperopic cases, and with corneal power in high hyperopic cases; 69.5% of variability in spherical equivalent was attributed to changes in these variables. In the second model, the correlations between vitreous chamber depth and corneal power with spherical equivalent were stronger in myopes than hyperopes, while the correlations between lens thickness and anterior chamber depth with spherical equivalent were stronger in hyperopic cases than myopic ones. In the third model, anterior chamber depth + lens thickness correlated with spherical equivalent only in moderate and severe cases of hyperopia, and this index was not correlated with spherical equivalent in moderate to severe myopia.

Conclusion:

In individuals aged 40-64 years, corneal power and axial length make the greatest contribution to spherical equivalent in high hyperopia and high myopia. Anterior segment biometric components have a more important role in hyperopia than myopia.

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.

Corneal elevation and keratoconus indices in a 40- to 64-year-old population, Shahroud Eye Study

Purpose

To determine the corneal elevation values and keratoconus indices in the 40- to 64-year-old population and their changes with aging.

Methods

The 6311 invitees of this study were selected through random cluster sampling, and 5190 of them participated in the study (response rate = 82.2%). Here, we analyzed results of Pentacam acquisitions in 4148 respondents. Cases of keratoconus and forme fruste keratoconus (FFKC) were determined using topography and clinical data. Studied variables included keratoconus indices, central corneal thickness readings, maximum elevations on the anterior and posterior surfaces, and elevation values at the thinnest point, anterior steepest point, and posterior steepest point in healthy, FFKC, and keratoconus groups.

Results

In all subjects, the mean maximum elevations were 6.80 ± 5.0 μm and 16.60 ± 7.7 μm on the anterior and posterior corneal surfaces, respectively. Maximum elevation values on the anterior and posterior corneal surfaces showed significant correlations in the keratoconus, FFKC, and healthy groups (P < 0.002). Maximum anterior elevation correlated with age (r = 0.11, P < 0.001), but maximum posterior elevation showed no such correlation (P = 0.476). Keratoconus indices demonstrated significant changes with age (P < 0.001).

Conclusion

Anterior elevation values slightly increase with age, and keratoconus indices change as well. Elevation readings and keratoconus indices in the keratoconus group and FFKC cases are higher than the healthy corneas although their values could be compared with other studies on younger participants.

Longitudinal changes in corneal curvature and its relationship to axial length in the Correction of Myopia Evaluation Trial (COMET) cohort

PURPOSE

To describe longitudinal changes in corneal curvature (CC) and axial length (AL) over 14 years, and to explore the relationship between AL and CC, and the axial length/corneal radius (AL/CR) ratio.

METHODS

In total 469, 6 to <12-year-old, children were enrolled in COMET. Measurements of refractive error, CC (D), CR (mm), and ocular component dimensions including AL were gathered annually. Linear mixed models were used to evaluate longitudinal changes adjusting for covariates (gender, ethnicity, lens type, baseline age and baseline refraction). The Pearson correlation coefficient between AL and CC was computed at each visit.

RESULTS

There was a slight but significant (p<0.0001) flattening in CC over 14 years. At all visits females had significantly steeper CC than males (overall difference=0.53 D, p<0.0001). Caucasians had the steepest CC, and Hispanics the flattest (p=0.001). The correlation between AL and CC was -0.70 (p<0.0001) at baseline (mean age=9.3 years) and decreased to -0.53 (p<0.0001) at the 14-year visit (mean age=24.1 years). The average AL/CR ratio was 3.15 at baseline and increased to 3.31 at the 14-year visit. The correlation between the magnitude of myopia and AL/CR ratio was significantly higher (p<0.0001) at each visit than the correlation between myopia and AL alone.

CONCLUSIONS

Differences in average corneal curvature by age, gender, and ethnicity observed in early childhood remain consistent as myopia progresses and stabilizes. This study also demonstrates increases in the AL/CR ratio as myopia progresses and then stabilizes, supporting observations from previous cross-sectional data.

Metabolic syndrome and its risk factors among middle aged population of Iran, a population based study

AIMS

To determine the prevalence of metabolic syndrome (MS) and its risk factors in a middle-aged population in Iran.

METHODS

The sample was 5190 individuals aged 40-64 years participated in the first phase of the Shahroud eye cohort study. Prevalence of MS was determined in terms of the age and sex. Other variables were evaluated by using simple and multiple logistic regression methods.

RESULTS

The prevalence of MS was 10.88% in men, 13.03% in women and 12.14% in total. The prevalence proportion increased with increasing age. In multivariate logistic regression model, age (odds ratio (OR)=1.06), education (OR=0.98) and smoking (OR=0.50), had significant effects on MS. In this model, gender, marital status and economic status had no significant effect on MS. Higher prevalence of obesity and overweight in non-smokers (79.9%) compare to smokers (47.4%, P<0.001), indicated that the association of smoking and MS is confounded.

CONCLUSIONS

Despite the low prevalence of MS in this study, older age was associated with increased risk of developing MS and higher education was associated with decreased this risk, therefore health education, changing the lifestyle, and taking greater attention in elderly is needed in order to prevent the MS and its complications.

Bushehr Elderly Health (BEH) Programme, phase I (cardiovascular system)

PURPOSE

The main objective of the Bushehr Elderly Health Programme, in its first phase, is to investigate the prevalence of cardiovascular risk factors and their association with major adverse cardiovascular events.

PARTICIPANTS

Between March 2013 and October 2014, a total of 3000 men and women aged ≥ 60 years, residing in Bushehr, Iran, participated in this prospective cohort study (participation rate=90.2%).

FINDINGS TO DATE

Baseline data on risk factors, including demographic and socioeconomic status, smoking and medical history, were collected through a modified WHO MONICA questionnaire. Vital signs and anthropometric measures, including systolic and diastolic blood pressure, weight, height, and waist and hip circumference, were also measured. 12-lead electrocardiography and echocardiography were conducted on all participants, and total of 10 cc venous blood was taken, and sera was separated and stored at -80 °C for possible future use. Preliminary data analyses showed a noticeably higher prevalence of risk factors among older women compared to that in men.

FUTURE PLANS

Risk factor assessments will be repeated every 5 years, and the participants will be followed during the study to measure the occurrence of major adverse cardiac events. Moreover, the second phase, which includes investigation of bone health and cognition in the elderly, was started in September 2015. Data are available at the Persian Gulf Biomedical Research Institute, Bushehr University of Medical Sciences, Bushehr, Iran, for any collaboration.