Ophthalmic epidemiology

Publisher: International Society of Geographical and Epidemiological Ophthalmology, Taylor & Francis


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    Ophthalmic epidemiology (Online)
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Publications in this journal

  • Ophthalmic epidemiology 06/2014; 21(3):135-7.
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    ABSTRACT: Abstract Aims: To identify the reasons for poor uptake of cataract surgery in a program of outreach screening and low-cost surgery in Pucheng County, a rural area in northwestern China. Methods: Detailed interviews with a semi-structured questionnaire were conducted by telephone or face-to-face for participants who had been advised to attend a low-cost cataract surgery program but did not schedule the surgery within 3 months after the initial screening. Results: Among 432 eligible subjects, 355 (82.2%) were interviewed (mean age 70.6 ± 6.6 years, 73.8% female). A total of 138 subjects (38.9%) were interviewed by phone and 217 (61.1%) were interviewed face-to-face. Lack of family support (n = 106, 29.9%) and failure to understand the need for surgery (n = 96, 27.0%) were the two main reasons for not undergoing cataract surgery. Other factors included fear of surgery (n = 62, 17.5%), lack of faith in doctors (n = 36, 10.1%), financial constraints (n = 25, 7.0%) and lack of transportation (n = 4, 1.1%). Conclusion: The principal barriers to low-cost cataract surgery uptake in rural China included lack of family support and failure to understand the need for surgery. Education targeting entire families to eliminate these barriers and development of community support systems at the family level are required to achieve greater uptake of low-cost cataract surgery programs in rural China.
    Ophthalmic epidemiology 04/2014;
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    ABSTRACT: Abstract Purpose: To estimate the prevalence, causes of and risk factors for vision loss in Upper Egypt. Methods: In this cross-sectional study, four villages in Upper Egypt were randomly selected; within these four villages, households were randomly selected and within the selected households all residents aged ≥40 years were enumerated and enrolled. Door-to-door eye examinations of household members were conducted. Data on relevant demographic and socioeconomic characteristics were collected. The prevalence and causes of vision loss and associated risk factors were assessed. Sex differences in prevalence and determinants were also evaluated. Results: The prevalence of best eye presenting visual impairment, severe visual impairment, and blindness were 23.9%, 6.4%, and 9.3% respectively. The prevalence of blindness among women significantly exceeded that among men (11.8% vs. 5.4%, respectively, p = 0.021). The prevalence of cataract was 22.9% (higher in women, 26.5% than men 17.2%, p = 0.018). The prevalence of trachomatous trichiasis was 9.7% (higher among women, 12.5%, than men, 5.4%, p = 0.012). The principal causes of blindness were cataract (60%), uncorrected refractive errors (16%) and corneal opacities (12%). Age, sex, family size, illiteracy, unemployment, water source and sanitation methods and living conditions were the major risk factors for vision loss. Conclusion: The prevalence of visual impairment remains high in Egypt, particularly among women. Risk factors for blindness may differ between men and women. There is a need for qualitative investigations to better understand the causes behind the excess in prevalence of blindness among women.
    Ophthalmic epidemiology 04/2014; 21(3).
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    ABSTRACT: Abstract Purpose: To assess the yearly incidence of vitrectomy for proliferative diabetic retinopathy (PDR) over an 11-year period, in a geographically defined part of North East England. The time period covered the introduction of diabetic retinopathy screening. Methods: All patients undergoing vitrectomy for diabetic retinopathy in the Sunderland and South Tyneside area were recorded from 2000 to 2010. Incidence rates of vitrectomy specifically for the complications of PDR for the observed diabetic population, the estimated diabetic population and the population with known PDR were calculated. Results: There was a gradual and significant decline in the vitrectomy rate from 157 (95% confidence interval, CI, 135-187) to 103 (95% CI 98-109) per 100,000 of the observed diabetic population in 2000 and 2010 respectively. The rate in the estimated diabetic population showed no significant change at 68 (95% CI 48-87) in 2002 and 77 (95% CI 55-103) in 2010. The rate in the PDR population, which comprised 2.4% of the known diabetic population in 2002 and 1.8% in 2010, declined significantly from 7.7% in 2002 to 5.7% in 2010. Conclusion: This study evaluated vitrectomy rates for PDR in an area of North East England. There were apparent declining rates of vitrectomy for PDR following the introduction of diabetic retinopathy screening but these have to be interpreted in the light of several confounding factors.
    Ophthalmic epidemiology 04/2014;
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    ABSTRACT: Abstract Purpose: To determine the prevalence of amblyopia and strabismus in 7th-grade junior high school students in central China. Methods: Using stratified cluster sampling, 2363 7th-grade students were recruited from four junior high schools in Anyang city into the cross-sectional Anyang Childhood Eye Study (ACES). All students underwent visual acuity (VA), cycloplegic autorefraction, cover test, and ocular movement examinations. Uncorrected VA and best-corrected VA (BCVA) were measured with a logarithm of the minimum angle of resolution (logMAR) chart. Cycloplegic autorefraction was performed after administration of 1.0% cyclopentolate and Mydrin-P. Strabismus was defined as heterotropia at near or distance fixation. Amblyopia was defined as BCVA≤0.1 logMAR units in one or both eyes, without ocular pathology in either eye. Results: Of the 2363 eligible students, 2260 (95.6%) completed all examinations. The mean age of the students was 12.4 ± 0.6 years. Amblyopia was present in 52 students (2.5%), of whom 33 (63.5%) had unilateral and 19 (36.6%) had bilateral amblyopia. Of those with unilateral amblyopia, 18 (54.5 %) had anisometropia and 7 (21.2%) had strabismus. Of those with bilateral amblyopia, 6 (31.6%) had significant refractive error. Strabismus was present in 108 students (5.0%), of whom 2 (1.9%) had esotropia, 102 (94.4%) had exotropia, 3 (2.8%) had vertical strabismus, and 1 (0.9%) had microstrabismus. Of the 108 students with strabismus, 9 (8.3%) had amblyopia. Conclusion: The cross-sectional ACES which examined the prevalence of amblyopia and strabismus in 7th-grade students in central China revealed the prevalence of strabismus, particularly the proportion of exotropia, to be higher than previously reported.
    Ophthalmic epidemiology 04/2014;
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    ABSTRACT: Abstract Purpose: To describe and assess an orthoptist-led vision screening service for school-entry (reception class) children, and report outcomes from one healthcare trust in the UK. Methods: A total of 3721 children (aged 4-5 years) in reception class primary school (155 state, 3 private) underwent orthoptist-conducted vision screening. Children who failed to meet the screening criteria were referred to hospital-based eye services for re-testing and final diagnosis. Results: The screening take-up rate was 96.41%; the remaining 3.59% refused/failed to consent to screening. The screening capture rate of participating children was 99.7%. A total of 11.14% of screened children failed to meet the screening criteria and were referred elsewhere; no abnormalities were found in 14% (false referral rate) of these children. Of the referred children, 53% had refractive errors requiring glasses and 42% had squints. The estimated percentages of common visual problems in screened children were 9.15% for refractive error and 3.81% for squint. Conclusion: An orthoptist-led, time-of-school-entry vision screening service is ideal for successful childhood vision screening and is, thus, a valuable source of information regarding the prevalence of common visual problems among children.
    Ophthalmic epidemiology 04/2014;
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    ABSTRACT: Abstract Purpose: To assess the associations between narrow angle and adult anthropometry. Methods: Chinese adults aged 50 years and older were recruited from a population-based survey in the Liwan District of Guangzhou, China. Narrow angle was defined as the posterior trabecular meshwork not visible under static gonioscopy in at least three quadrants (i.e. a circumference of at least 270°). Logistic regression models were used to examine the associations between narrow angle and anthropomorphic measures (height, weight and body mass index, BMI). Results: Among the 912 participants, lower weight, shorter height, and lower BMI were significantly associated with narrower angle width (tests for trend: mean angle width in degrees vs weight p < 0.001; vs height p < 0.001; vs BMI p = 0.012). In univariate analyses, shorter height, lower weight and lower BMI were all significantly associated with greater odds of narrow angle. The crude association between height and narrow angle was largely attributable to a stronger association with age and sex. Lower BMI and weight remained significantly associated with narrow angle after adjustment for height, age, sex, axial ocular biometric measures and education. In analyses stratified by sex, the association between BMI and narrow angle was only observed in women. Conclusion: Lower BMI and weight were associated with significantly greater odds of narrow angle after adjusting for age, education, axial ocular biometric measures and height. The odds of narrow angle increased 7% per 1 unit decrease in BMI. This association was most evident in women.
    Ophthalmic epidemiology 04/2014; 21(3).
  • Ophthalmic epidemiology 04/2014; 21(2):133.
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    ABSTRACT: Abstract Purpose: Trachoma is the leading cause of blindness from infection worldwide. Treatment programs require accurate Chlamydia trachomatis infection prevalence rates to guide decision making. The use of clinical examination is by far the most common way to monitor activity, but may yield overestimates of infection prevalence. Laboratory testing on individual specimens such as polymerase chain reaction (PCR) is highly sensitive and specific, but prohibitively expensive. Here we demonstrate simulations of pooled PCR results may estimate infection prevalence of an entire community yielding substantial cost savings if pool size is chosen correctly. Methods: Community infection prevalence was estimated using maximum likelihood estimation with data collected from a previously described study. Simulations for communities were performed to determine the accuracy of prevalence estimation using pooled results. The root mean squared error was then used to determine an acceptable inaccuracy in estimates allowing for a pooling strategy to be formed. Results: Results from simulations and empirical data suggest optimum pooling strategies to estimate community infection prevalence while keeping the root mean squared error of the estimate below 2%. Reduction of PCR testing which permits cost savings is shown to be between 5 and 80% given a community infection prevalence below 60%. Conclusions: Pooling specimens for PCR testing often provides enough data to accurately estimate infection prevalence at the community level.
    Ophthalmic epidemiology 04/2014; 21(2):86-91.
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    ABSTRACT: Abstract Purpose: The aim of this study was to estimate utility values associated with different severity stages of diabetic retinopathy (DR) in India by a direct elicitation method (time-trade off, TTO) and indirectly by questionnaire. Methods: People with diabetes aged 40 years and over were recruited from an on-going DR epidemiology study and a laser clinic in Chennai, India. Utility values were elicited using the direct TTO method and indirectly through a validated questionnaire (EQ-5D). Results: Of 249 participants, 30 had no DR, 73 had non-proliferative DR, 114 had sight-threatening DR, and 32 were blind from DR (bilateral visual acuity <6/60). The mean TTO utility value was 0.73 (standard deviation, SD, 0.31). TTO utility values decreased with increasing severity of DR (p < 0.001) and were significantly lower among participants with sight threatening DR (0.70, SD 0.33) and blindness (0.55, SD 0.24) compared to those with no DR (0.89, SD 0.25) after adjustment for sociodemographic and clinical factors. Blindness from DR was independently associated with a lower EQ-5D utility value. The utility value derived from EQ-5D (0.06) associated with being blind from DR was substantially lower than that of the TTO utility value (0.55). Conclusions: This study provides estimates of utility values that can be used in economic evaluations of DR screening strategies in India. The relatively low utility values associated with blindness highlights the importance of screening programs for early detection of the sight-threatening stages to prevent vision loss from DR in this setting.
    Ophthalmic epidemiology 03/2014;
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    ABSTRACT: Abstract Purpose: To examine the demographic, sociocultural and socioeconomic factors that prevent families of cataract blind children from accepting free pediatric cataract surgery in Malawi. Methods: A total 58 parents of 62 children were recruited into the study. Of these, 53 parents partook in in-depth interviews and focus group discussions after the children were screened and the parents offered free cataract surgery. Overall, 37 parents accepted (acceptors) and 16 parents did not accept (non-acceptors) cataract surgery. All interviews were transcribed and iteratively analyzed. Household economic status was quantified using the Progress out of Poverty Index for Malawi. Results: Acceptors were better off economically (p = 0.13). Understanding of cataract, its causing blindness and impairment, as well as treatment options, by the decision makers in the families was poor. Decision-making involved a complex array of aspects needing consideration before accepting, of which distance to the health facility was a frequently mentioned barrier. Non-acceptors were more likely to come from twice the distance compared to acceptors (p = 0.0098). Non-acceptors were more likely to be peasant (subsistence) farmers than acceptors (p = 0.048). Non-acceptors were more likely to live in a house made of mud bricks with a roof of grass thatch (p = 0.001). There was no significant difference in acceptance rate between educated and non-educated mothers (p = 0.11). Intensive counseling as provided in this project increased the likelihood of accepting surgery. Conclusion: Economic hardship and long distances to health facilities decrease acceptance even of free pediatric cataract surgical services, highlighting that just providing surgery free of cost may not be sufficient for the most economically disadvantaged in rural Africa.
    Ophthalmic epidemiology 03/2014; 21(3).
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    ABSTRACT: Abstract Purpose: To compare methodologies for imputing ethnicity in an urban ophthalmology clinic. Methods: Using data from 19,165 patients with self-reported ethnicity, surname, and home address, we compared the accuracy of three methodologies for imputing ethnicity: (1) a surname method based on tabulation from the 2000 US Census; (2) a geocoding method based on tract data from the 2010 US Census; and (3) a combined surname geocoding method using Bayes' theorem. Results: The combined surname geocoding model had the highest accuracy of the three methodologies, imputing black ethnicity with a sensitivity of 84% and positive predictive value (PPV) of 94%, white ethnicity with a sensitivity of 92% and PPV of 82%, Hispanic ethnicity with a sensitivity of 77% and PPV of 71%, and Asian ethnicity with a sensitivity of 83% and PPV of 79%. Overall agreement of imputed and self-reported ethnicity was fair for the surname method (κ 0.23), moderate for the geocoding method (κ 0.58), and strong for the combined method (κ 0.76). Conclusion: A methodology combining surname analysis and Census tract data using Bayes' theorem to determine ethnicity is superior to other methods tested and is ideally suited for research purposes of clinical and administrative data.
    Ophthalmic epidemiology 02/2014; 21(2).
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    ABSTRACT: Abstract Purpose: To develop a mapping algorithm for the estimation of EQ-5D-based utility scores from observed 25-item National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) scores, a disease-specific, patient-reported outcome measure used in several retinal disorders to evaluate vision-specific functioning. Methods: The dataset comprised 951 paired EQ-5D/NEI VFQ-25 observations from 344 patients in RESTORE, a 12-month, randomized, double-blind trial in individuals with visual impairment due to diabetic macular edema. EQ-5D index scores (utilities) were calculated based on the UK tariff. We evaluated 11 models using predictor sets based on the NEI VFQ-25 subscales to estimate utility as a function of NEI VFQ-25 score, based on four modeling techniques. Model performance was assessed by 10-fold cross-validation comparing root mean squared error (RMSE), mean absolute error (MAE) and correlation with EQ-5D score (Pearson and Spearman correlation coefficients). Results: Mapping results were similar across all techniques and predictor sets. The reverse two-part generalized estimating equation model used fewest predictors and had the best predictive performance (RMSE 0.200, MAE 0.140). Predicted and original EQ-5D values were not strongly correlated (squared Spearman correlation coefficient, 0.34). Conclusions: Although mapping disease-specific instruments to EQ-5D utilities is a preferred method by some reimbursement bodies, finding an appropriate mapping equation is not straightforward. In this study, mapping NEI VFQ-25 scores to EQ-5D utilities provided low predictive power, independent of the modeling methodology applied, suggesting an inability of the EQ-5D to discriminate vision-related activities, and highlighting that mapping exercises may lead to inaccurate utility values that do not represent patients' preferences.
    Ophthalmic epidemiology 02/2014;
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    ABSTRACT: Abstract Purpose: To examine the association of reproductive factors and major eye diseases, including glaucoma, age-related macular degeneration (AMD), diabetic retinopathy and cataract, in Asian women. Methods: The Singapore Malay Eye Study is a population-based cross-sectional epidemiological study which examined 3280 persons (78.7% response) of Malay ethnicity aged 40-80 years; 1704 were female. Information on reproductive factors and use of hormone replacement therapy (HRT) was collected using an interviewer-administered questionnaire. Glaucoma was defined according to the International Society for Geographical and Epidemiological Ophthalmology criteria. Retinal photographs were graded for AMD following the Wisconsin grading system, and diabetic retinopathy according to the modified Airlie House classification system. Cataract was graded according to the Lens Opacity Classification System III. Results: A total of 1176 women reported having experienced menopause by the time of the study with 1073 (91%) having a natural menopause, 88 (7.5%) a hysterectomy and 9 (0.8%) due to other reasons; HRT was used by 70 (6%) women. Women whose age at menopause was ≤52 years were 3.5 times more likely to have glaucoma (95% confidence interval, CI, 1.23-9.98, p value = 0.02) than those whose age at menopause was ≥53 years. Age of menopause was not associated with AMD (age-adjusted odds ratio, OR, 1.22, 95% CI 0.65-2.31), diabetic retinopathy (age-adjusted OR 1.01, 95% CI 0.66-1.54) or cataract (age-adjusted OR 1.38, 95% CI 0.95-2.00). Use of HRT was not associated with any of these eye diseases. Conclusion: Women who had menopause at a younger age were more likely to have glaucoma. This association needs to be confirmed in other studies.
    Ophthalmic epidemiology 02/2014;