Ecosse L. Lamoureux

Global prevalence and major risk factors of diabetic retinopathy

OBJECTIVE To examine the global prevalence and major risk factors for diabetic retinopathy (DR) and vision-threatening diabetic retinopathy (VTDR) among people with diabetes. RESEARCH DESIGN AND METHODS A pooled analysis using individual participant data from population-based studies around the world was performed. A systematic literature review was conducted to identify all population-based studies in general populations or individuals with diabetes who had ascertained DR from retinal photographs. Studies provided data for DR end points, including any DR, proliferative DR, diabetic macular edema, and VTDR, and also major systemic risk factors. Pooled prevalence estimates were directly age-standardized to the 2010 World Diabetes Population aged 20–79 years. RESULTS A total of 35 studies (1980–2008) provided data from 22,896 individuals with diabetes. The overall prevalence was 34.6% (95% CI 34.5–34.8) for any DR, 6.96% (6.87–7.04) for proliferative DR, 6.81% (6.74–6.89) for diabetic macular edema, and 10.2% (10.1–10.3) for VTDR. All DR prevalence end points increased with diabetes duration, hemoglobin A1c, and blood pressure levels and were higher in people with type 1 compared with type 2 diabetes. CONCLUSIONS There are approximately 93 million people with DR, 17 million with proliferative DR, 21 million with diabetic macular edema, and 28 million with VTDR worldwide. Longer diabetes duration and poorer glycemic and blood pressure control are strongly associated with DR. These data highlight the substantial worldwide public health burden of DR and the importance of modifiable risk factors in its occurrence. This study is limited by data pooled from studies at different time points, with different methodologies and population characteristics.

Methodology of the Singapore Indian Chinese Cohort (SICC) eye study: Quantifying ethnic variations in the epidemiology of eye diseases in Asians

Purpose: Current knowledge of ethnic variability in the epidemiology of major eye diseases in Asia is limited. This report summarizes the rationale and study design of the Singapore Indian Chinese Cohort (SICC) Eye Study, a population-based study of ethnic South Asian (Indians) and East Asian (Chinese) older adults in Singapore. Methods: The SICC examined a population-based cross-sectional sample of 3,300 ethnic Indians and 3,300 ethnic Chinese aged 40–80+ years residing in the South-Western part of Singapore. Results: From two lists of 12,000 names of each ethnic group provided by the Ministry of Home Affairs, age-stratified random sampling was used to select 6,350 names in each group, with a target sample size of 3,300. Invitations were sent to attend a central clinic using letters, telephone calls and home visits. Examination procedures included interviews, measurement of blood pressure, anthropometry, presenting and best-corrected visual acuity, subjective refraction, ocular biometry, Goldmann applanation tonometry, slit-lamp biomicroscopy, optic disc imaging and digital photography of the lens and retina, using a standardized protocol. Selected participants underwent gonioscopic examination, visual field testing, and anterior and posterior segment optical coherence tomography. Blood, tear, and urine samples were collected for biochemical analyses, and stored for genetic and proteomic studies. Conclusions: In conjunction with the Singapore Malay Eye Study, the SICC study will permit an in-depth evaluation of the prevalence, risk factors, and impact of major eye diseases in Chinese, Indians and Malays, three distinct Asian ethnic groups, whose combined numbers represent half the world’s population.

Impact of age related macular degeneration on quality of life

Aims: To describe the impact of age related macular degeneration (AMD) on quality of life and explore the association with vision, health, and demographic variables. Methods: Adult participants diagnosed with AMD and with impaired vision (visual acuity <6/12) were assessed with the Impact of Vision Impairment (IVI) questionnaire. Participants rated the extent that vision restricted participation in activities affecting quality of life and completed the Short Form General Health Survey (SF-12) and a sociodemographic questionnaire. Results: The mean age of the 106 participants (66% female) was 83.6 years (range 64–98). One quarter had mild vision impairment, (VA<6/12–6/18) and 75% had moderate or severely impaired vision. Participants reported from at least “a little” concern on 23 of the 32 IVI items including reading, emotional health, mobility, and participation in relevant activities. Those with mild and moderate vision impairment were similarly affected but significantly different from those with severe vision loss (p<0.05). Distance vision was associated with IVI scores but not age, sex, or duration of vision loss. Conclusion: AMD affects many quality of life related activities and not just those related to reading. Referral to low vision care services should be considered for people with mild vision loss and worse.

Remediating serious flaws in the National Eye Institute Visual Function Questionnaire

PURPOSE: To test the assumption that the National Eye Institute Visual Function Questionnaire (NEI VFQ) measures visual functioning, assess the validity of its subscales, and, if flawed, revise the questionnaire and derive a shortened version with sound psychometric properties. SETTING: Flinders Medical Centre, Adelaide, Australia. METHODS: Patients from the cataract surgery waiting list self‐administered and completed the 39‐item NEI VFQ (NEI VFQ‐39). Rasch analysis was applied, and the psychometric performance of the entire questionnaire and each subscale was tested. Instrument revision was performed in the context of Rasch analysis statistics. RESULTS: Five hundred thirty‐six patients (mean age 73.8 years) completed the questionnaire. Response categories for 2 question types were not used as intended so dysfunctional categories were combined. The NEI VFQ‐39 and the 25‐item version (NEI VFQ‐25) had good precision but evidence of multidimensionality (more than 1 construct in 1 score), questions that did not fit the construct, suboptimum targeting of item difficulty to person ability, and dysfunctional subscales (8 NEI VFQ‐39; 12 NEI VFQ‐25). Questions could be reorganized into 2 constructs (a visual functioning scale and a socioemotional scale) that, after misfitting questions were removed, gave valid measurement of each construct and preserved 3 subscales. Removing redundancy from these long‐form subscales yielded valid short‐form scales. CONCLUSIONS: Several NEI VFQ subscales were not psychometrically sound; as an overall measure, it is flawed by multidimensionality. This was repaired by segregation into visual functioning and socioemotional scales. Valid long and short forms of the scales could enhance application of the questionnaire. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

The Psychometric Validity of the NEI VFQ-25 for Use in a Low-Vision Population

PURPOSE To determine the psychometric validity of the National Eye Institute-Visual Function Questionnaire (NEI VFQ-25) and its subscale structure for use in people with low vision. METHODS Two hundred thirty-two participants completed the NEI VFQ-25. Rasch analysis was used to test the psychometric performance of the questionnaire and each subscale. Factor models were hypothesized and tested with confirmatory factor analysis (CFA) and subsequently validated with Rasch analysis. RESULTS For the overall scale, two rating scales had to be dichotomized and three misfitting items removed to improve fit to the Rasch model. There was evidence of multidimensionality, indicating that the scale would benefit from scale splitting. For the NEI VFQ-25 subscale structure, six of the original 12 subscales could not fit the Rasch model because of item insufficiency (fewer than two items) and the remaining six displayed poor item fit characteristics indicating that the NEI VFQ-25 does not have a viable subscale structure. CFA supported a two-factor model with visual functioning (10 items) and socioemotional (9 items) scales. Most goodness-of-fit statistics were within the recommended range of values. The factor loadings of items on their respective scales were statistically significant (P < 0.001) and ranged between 0.59 and 0.84. The two scales individually fitted the Rasch model and were found to be unidimensional with adequate psychometric characteristics. CONCLUSIONS The native NEI VFQ-25 is a better performing instrument when split into visual functioning and socioemotional scales. These scales possess valid parameters for assessment of the impact of low vision in this population.

Associations between glaucomatous visual field loss and participation in activities of daily living

Purpose: This study investigated the association between visual field loss and participation in daily activities in individuals with glaucoma.

Barriers to accessing low vision services.

Aim: To investigate barriers to accessing low vision services in Australia.

Prevalence and Causes of Visual Impairment and Blindness in an Urban Indian Population: The Singapore Indian Eye Study

PURPOSE To describe the prevalence and causes of visual impairment and blindness in an urban Indian population. DESIGN Population-based study. PARTICIPANTS Ethnic Indians aged more than 40 years living in Singapore. METHODS Participants underwent standardized ophthalmic assessments for visual impairment and blindness, defined using best-corrected visual acuity (BCVA) and presenting visual acuity (PVA), according to US and modified World Health Organization (WHO) definitions. MAIN OUTCOME MEASURES Unilateral visual impairment or blindness was defined on the basis of the worse eye, and bilateral visual impairment or blindness was defined on the basis of the better eye. Primary causes of visual impairment were determined. RESULTS A total of 3400 eligible individuals (75.6% response rate) participated. On the basis of US definitions, the age-standardized prevalence was 0.4% for bilateral blindness (≤20/200, better eye) and 3.4% for bilateral visual impairment (<20/40 to >20/200, better eye). Another 0.3% of bilateral blindness and 13.4% of bilateral visual impairment were correctable with refraction. Cataract was the principal cause of best-corrected bilateral blindness (60.0%) and bilateral visual impairment (65.7%). Other major causes of blindness and visual impairment included diabetic retinopathy, age-related macular degeneration, glaucoma, corneal opacity, and myopic maculopathy. CONCLUSIONS The prevalence of bilateral blindness and visual impairment in Indians living in Singapore is lower than estimates from populations living in India, but similar to estimates obtained from Singapore Malay and Chinese populations. Cataract is the leading cause of blindness and visual impairment. One in 20 cases of bilateral blindness and 1 in 10 cases of bilateral visual impairment are attributable to diabetic retinopathy. These data may have relevance to many ethnic Indian persons living outside India.

The effects of improved strength on obstacle negotiation in community-living older adults

Poor mobility has been associated with age-related deterioration in muscle strength. While previous work has examined the effects of improved strength on level walking, we have quantified the effects of a resistance-training program on obstructed gait tasks using biomechanical-dependent measures. Forty-five community-dwelling participants aged 62 years or older were randomised to either a control (n=16) or experimental group (n=29). The experimental subjects exercised for 24 weeks on a progressive resistance-training program designed to improve lower body strength. Dynamic strength was assessed at weeks 0 and 24 as well as specific laboratory gait kinetics and kinematics during stepping over an obstacle and negotiation of a raised surface set at 10, 20 and 30% of each subjects leg length. Significant strength improvements (P<0.05), ranging between 197 and 285%, were recorded in the experimental group. The strength gains in the experimental group were accompanied by significant increases in obstacle-crossing stride velocity (range 5.5-15.5%) due to increases in stride length and decreases in stride duration for both gait tasks. Significant changes in the peak vertical and anterior-posterior ground reaction forces as well as in kinematic variables associated with a safe obstacle traverse such as vertical obstacle heel clearance, limb flexion at obstacle crossing, horizontal foot placement and vertical landing velocity resulted in an improved crossing strategy in the experimental subjects. These findings provide evidence of significant improvements in obstructed gait function of community-living older adults associated with a systematic resistance-training program.

C-reactive protein, body mass index, and diabetic retinopathy.

PURPOSE C-reactive protein (CRP) is an inflammatory biomarker that may be associated with diabetic retinopathy (DR), but body mass index (BMI) is an important confounder of this relationship. The purpose of this study was to determine the relationship between CRP, BMI, and existing DR. METHODS This was a population-based, cross-sectional study on 718 persons with diabetes in the Singapore Malay Eye Study (SiMES). Diabetes was defined as random glucose>or=11.1 mmol/L, on diabetic medication or a history of physician-diagnosed diabetes. CRP was measured in frozen plasma. DR was graded from retinal photographs. RESULTS Higher CRP and BMI were associated with lower prevalence of DR. After adjustment for age, sex, HbA1c level, hypertension, smoking, total cholesterol level, cholesterol-lowering medication, and insulin use, persons with the highest quartiles of CRP were less likely to have any DR (odds ratio [OR] 0.5; 95% CI, 0.3-0.9, comparing the fourth with the first quartile of CRP), vision-threatening DR (OR 0.3; 95% CI, 0.1-0.7), or CSME (OR 0.2; 95% CI, 0.1-0.6). Similarly, persons with the highest quartiles of BMI were less likely to have any DR (OR 0.5; 95% CI, 0.3-0.7), moderate DR (OR 0.4; 95% CI, 0.2-0.7), vision-threatening DR (OR 0.4; 95% CI, 0.1-0.8) or CSME (OR 0.2; 95% CI, 0.0-1.0). No significant interactions between CRP and BMI on DR were seen. CONCLUSIONS Persons with diabetes who had higher levels of CRP and BMI were less likely to have DR. Further research is needed to understand the interrelationship role of inflammation, body weight, and microvascular complications.