Predicting participation of people with impaired vision in epidemiological studies.
ABSTRACT: The characteristics of the target group and the design of an epidemiologic study, in particular the recruiting methods, can influence participation. People with vision impairment have unique characteristics because those invited are often elderly and totally or partially dependent on help to complete daily activities such as travelling to study sites. Therefore, participation of people with impaired vision in studies is less predictable than predicting participation for the general population.Participants were recruited in the context of a study of prevalence and costs of visual impairment in Portugal (PCVIP-study). Participants were recruited from 4 Portuguese public hospitals. Inclusion criteria were: acuity in the better eye from 0.5 decimal (0.30logMAR) or worse and/or visual field of less than 20 degrees. Recruitment involved sending invitation letters and follow-up phone calls. A multiple logistic regression model was used to assess determinants of participation. The J48 classifier, chi-square and Fisher's exact tests were applied to investigate the possible differences between subjects in our sample.Individual cases were divided into 3 groups: immediate, late and non-participants. A participation rate of 20% was obtained (15% immediate, 5% late). Factors positively associated with participation included years of education, annual hospital attendance, and intermediate visual acuity. Females and greater distance to the hospital were inversely associated with participation.In our study, a letter followed by a phone call was efficient to recruit a significant number of participants from a larger group of people with impaired vision. However, the improvement in participation observed after the phone call might not be cost-effective. People with low levels of education and women were more difficult to recruit. These findings need to be considered to avoid studies whose results are biased by gender or socio-economic inequalities of their participants. Young subjects and those at intermediate stages of vision impairment, or equivalent conditions, may need more persuasion than other profiles.
Project description:BACKGROUND:An association between visual impairment and cognitive outcomes has been documented, but there is limited research examining this relationship using multiple measures of vision. METHODS:Participants included non-demented individuals in Year 3 of the Visual impairment was assessed using visual acuity, contrast sensitivity, and stereo acuity. Cognitive function was defined using the digit symbol test and the Modified Mini-Mental State Examination (3MS). Incident cognitive impairment was defined as a 3MS score <80 or a decline >5 points following Year 3. Linear mixed effects models examined longitudinal associations adjusting for year, age, sex, race, education, smoking, depression, diabetes, study site, as well as interaction terms between the vision parameters and years in study, between baseline age and years in study, and quadratic terms of baseline age and years in study. Discrete Cox regression models examined the risk of incident cognitive impairment. RESULTS:Analyses included 2,444 participants (mean age = 74). Visual acuity, contrast sensitivity, and stereo acuity impairments were not associated with statistically significant changes in annual digit symbol test scores over 7 years of follow-up, as compared to those without these impairments. However, visual acuity, contrast sensitivity, and stereo acuity impairments were associated with greater declines in annual 3MS scores over 9 years. Participants with impaired visual acuity, contrast sensitivity, and stereo acuity had a greater risk of incident cognitive impairment. CONCLUSIONS:Our results suggest that visual acuity, contrast sensitivity, and stereo acuity impairments may be risk factors for cognitive decline.
Project description:To describe the cumulative 6-year incidence of visual impairment (VI) and blindness in an adult Kenyan population. The Nakuru Posterior Segment Eye Disease Study is a population-based sample of 4414 participants aged ?50 years, enrolled in 2007-2008. Of these, 2170 (50%) were reexamined in 2013-2014.The World Health Organization (WHO) and US definitions were used to calculate presenting visual acuity classifications based on logMAR visual acuity tests at baseline and follow-up. Detailed ophthalmic and anthropometric examinations as well as a questionnaire, which included past medical and ophthalmic history, were used to assess risk factors for study participation and vision loss. Cumulative incidence of VI and blindness, and factors associated with these outcomes, were estimated. Inverse probability weighting was used to adjust for nonparticipation.Visual acuity measurements were available for 2164 (99.7%) participants. Using WHO definitions, the 6-year cumulative incidence of VI was 11.9% (95%CI [confidence interval]: 10.3-13.8%) and blindness was 1.51% (95%CI: 1.0-2.2%); using the US classification, the cumulative incidence of blindness was 2.70% (95%CI: 1.8-3.2%). Incidence of VI increased strongly with older age, and independently with being diabetic. There are an estimated 21 new cases of VI per year in people aged ?50 years per 1000 people, of whom 3 are blind. Therefore in Kenya we estimate that there are 92,000 new cases of VI in people aged ?50 years per year, of whom 11,600 are blind, out of a total population of approximately 4.3 million people aged 50 and above.The incidence of VI and blindness in this older Kenyan population was considerably higher than in comparable studies worldwide. A continued effort to strengthen the eye health system is necessary to support the growing unmet need in an aging and growing population.
Project description:Background:Although there are limited studies, recent data are lacking to determine the prevalence of eye problems in Ethiopia accurately and there is no scientific evidence of such study in Sekela Woreda. The purpose of this study was to determine the prevalence of visual impairment among school children in Sekela Woreda, Ethiopia. Methods:The study design was a community-based analytical cross-sectional with a multi-stage cluster random sampling technique from September to November 2016.Visual acuity was tested using Snellen's "E" chart while color vision was tested using Ishihara chart. The data were analyzed using SPSS version 20 software, and binary logistic regression was used to identify factors associated with visual impairment. Results:A total of 875 participants, 466 (53.3%) males and 409 (46.7%) females, with an age range of 8-18?years were screened for visual acuity and color vision deficiency. The prevalence of visual impairment (visual acuity???6/12) in "either eye" was 70 (8.0%). Among these, 37 (52.9%) were males and 33 (41.1%) were females. The prevalence of low vision (visual acuity ?6/36 ) and blindness (visual acuity?<?3/60) in "either eye" were 28 (3.2%) and 10 (1.1%), respectively. Thirty two (3.7%) had mild visual impairment (visualacuity?6/12to?6/18) . The prevalence of color vision deficiency was 36 (4.1%). Among these, 27 (3%) were males and 9 (1.1%) were females. The variables age (adjusted odds ratio (95% confidence interval)?=?1.14 (1.01-1.28) and color blindness (adjusted odds ratio (95% confidence interval)?=?3.93(1.69-9.09) were significantly associated with visual impairment. Conclusion:The prevalence of blindness and low vision in school children were higher than the national prevalence in Ethiopia. Increasing age and color defective vision were factors associated with the children's visual impairment. The Woreda health office ought to work with responsible stakeholders to tackle the situation in early childhood.
Project description:BACKGROUND:Hearing impairment, vision impairment, and dual impairment (both hearing and vision impairment), have been independently associated with functional and cognitive decline. In prior studies of dual impairment, vision impairment is generally not defined or defined by visual acuity alone. Glaucoma is a leading cause of blindness and does not affect visual acuity until late in the disease; instead, visual field loss is used to measure vision impairment from glaucoma. OBJECTIVE:To examine the effect of glaucomatous visual field loss and hearing impairment on function. DESIGN:Cross-sectional. SETTING:Hospital-based clinic in Baltimore, Maryland. SUBJECTS:220 adults, ?55 years presenting to the glaucoma clinic. METHODS:Vision impairment was defined as mean deviation on visual field testing worse than -5 decibels in the better eye, and hearing impairment was defined as pure tone average worse than 25 decibels on threshold audiometry testing in the better ear. Standardized questionnaires were used to assess functional status. RESULTS:Five participants were excluded for incomplete testing, leaving 32 with vision impairment only, 63 with hearing impairment only, 42 with dual impairment, and 78 controls with no hearing impairment or vision impairment. Participants with dual impairment were more likely to be older and non-White. Dual impairment was associated with significantly more severe driving limitation and more difficulty with communication compared to those without sensory impairment when adjusted for age, race, gender and number of comorbidities. CONCLUSION:Older individuals with glaucoma and hearing loss seem to have generally poorer functioning than those with single sensory loss. Health professionals should consider visual field loss as a type of vision impairment when managing patients with dual impairment.
Project description:IMPORTANCE:This study provides further evidence from a national sample to generalize the relationship between depression and vision loss to adults across the age spectrum. Better recognition of depression among people reporting reduced ability to perform routine activities of daily living due to vision loss is warranted. OBJECTIVES:To estimate, in a national survey of US adults 20 years of age or older, the prevalence of depression among adults reporting visual function loss and among those with visual acuity impairment. The relationship between depression and vision loss has not been reported in a nationally representative sample of US adults. Previous studies have been limited to specific cohorts and predominantly focused on the older population. DESIGN:The National Health and Nutrition Examination Survey (NHANES) 2005-2008. SETTING:A cross-sectional, nationally representative sample of adults, with prevalence estimates weighted to represent the civilian, noninstitutionalized US population. PARTICIPANTS:A total of 10 480 US adults 20 years of age or older. MAIN OUTCOME MEASURES:Depression, as measured by the 9-item Patient Health Questionnaire depression scale, and vision loss, as measured by visual function using a questionnaire and by visual acuity at examination. RESULTS:In 2005-2008, the estimated crude prevalence of depression (9-item Patient Health Questionnaire score of ?10) was 11.3% (95% CI, 9.7%-13.2%) among adults with self-reported visual function loss and 4.8% (95% CI, 4.0%-5.7%) among adults without. The estimated prevalence of depression was 10.7% (95% CI, 8.0%-14.3%) among adults with presenting visual acuity impairment (visual acuity worse than 20/40 in the better-seeing eye) compared with 6.8% (95% CI, 5.8%-7.8%) among adults with normal visual acuity. After controlling for age, sex, race/ethnicity, marital status, living alone or not, education, income, employment status, health insurance, body mass index, smoking, binge drinking, general health status, eyesight worry, and major chronic conditions, self-reported visual function loss remained significantly associated with depression (overall odds ratio, 1.9 [95% CI, 1.6-2.3]), whereas the association between presenting visual acuity impairment and depression was no longer statistically significant. CONCLUSIONS AND RELEVANCE:Self-reported visual function loss, rather than loss of visual acuity, is significantly associated with depression. Health professionals should be aware of the risk of depression among persons reporting visual function loss.
Project description:Purpose:To explore the psychometric properties of the Impact of Vision Impairment (IVI-28) and Night Vision Questionnaires (NVQ-10) among people with intermediate age-related macular degeneration (iAMD). Methods:Baseline responses were collected from 288 participants (aged 50-88 years, 74% female) in the Laser intervention in Early stages of Age-related macular Degeneration (LEAD) study in Australia and Northern Ireland. Psychometric properties (discrimination, ordering of thresholds, person separation, item miss-fit, and differential item functioning according to sex) were explored using grouped rating scale and partial credit models. Spearman's correlation was estimated to assess the association with measures of visual function (mean mesopic microperimetric sensitivity, best-corrected visual acuity, low-luminance visual acuity, and low-luminance deficit). The psychometric properties were then explored following recalibration of the instruments. Results:In this homogenous population, ceiling effects caused by relatively high levels of functional vision were evident for both instruments. The IVI-28 and NVQ-10 displayed suboptimal discrimination between levels of functional vision in iAMD and poor targeting among people with iAMD. The correlation between ability scores and measures of visual function was mild. In general, the NVQ-10 showed superior psychometric properties to the IVI-28 among these participants. No significant improvement in reliability could be gained following recalibration. Conclusions:Both instruments were designed for populations with more severe visual loss and poorly discriminate in this cohort of iAMD. Translational Relevance:New instruments that can capture the subtle changes in functional vision that occur early in AMD are required to aid evaluation of emerging interventions for iAMD.
Project description:BACKGROUND:Older adults with visual impairments are at increased risk of negative health outcomes. Here, we investigate the association between visual impairment and frailty. METHODS:Cross-sectional and longitudinal relationships between visual impairment (distance visual acuity) and frailty (frailty phenotype criteria) were examined using data from the National Health and Nutrition Examination Survey (NHANES, 1999-2002, ?60 years) and the Women's Health and Aging Studies (WHAS III). Imbalance of potential confounders, particularly age, was addressed using propensity score-based adjustment. Multinomial logistic regression determined the odds of prefrailty and frailty at baseline in NHANES and ordinal logistic regression examined the odds of baseline and incident frailty over 3 years in WHAS III after adjustment for confounders and probability weighting (survey weights × inverse propensity scores). RESULTS:In NHANES (n = 2,639, 9% vision impairment), participants with visual impairment were more likely to be prefrail (odds ratio [OR] = 3.2; 95% confidence interval [CI]: 1.9-5.3) and frail (OR = 3.7; 95% CI: 1.5-9.2) than those without visual impairment. In WHAS III (n = 796, 26% mild, 37% moderate/severe vision impairment), participants with mild and moderate/severe vision impairment were more likely to be frail (OR = 2.0; 95% CI: 1.5-2.5; OR = 5.5; 95% CI: 4.2-7.2, respectively). A one-line worse visual acuity (0.1 logMAR increase) was associated with greater odds of frailty (OR = 1.5; 95% CI: 1.4-1.7). Of those non-frail at baseline (n = 549), moderate/severe visual impairment and one-line worse visual acuity was associated with greater odds of incident frailty (OR = 3.5; 95% CI: 1.4-8.4; OR = 1.3; 95% CI: 1.1-1.5, respectively) over 3 years. CONCLUSIONS:Visual impairment may be an important, yet understudied risk factor for frailty.
Project description:<h4>Purpose</h4>To evaluate the prevalence and causes of visual impairment in a group of community people with type 2 diabetes mellitus (T2DM) in Northeast China.<h4>Methods</h4>Population-based cross-sectional survey. Patients diagnosed with T2DM residing in 15 communities in Fushun, Northeast China, were enrolled between July 2012 and May 2013. All participants underwent an extensive and standardized eye examination (visual acuity testing, slit-lamp, and fundus examination). Low vision was defined as presenting VA of better-seeing eye <20/60 and ?20/400, and blindness was defined as VA <20/400, according to the World Health Organization (WHO) definitions. The primary causes of blindness and low vision were assessed by senior ophthalmologists.<h4>Results</h4>Visual acuity measurements were available for 1998 (89.8%) of 2224 subjects in the study. The prevalence of bilateral blindness and low vision defined was 0.90% and 10.81%. Uncorrected refractive error was the first leading cause of low vision (75.0%) and blindness (38.9%). After correcting the refractive error, the first leading cause of low vision was cataract (44.4%), followed by diabetic retinopathy (29.6%) and myopic maculopathy (18.5%), while the first leading cause of blindness was proliferative DR (45.4%), followed by cataract (36.4%) and myopic maculopathy (18.2%).<h4>Conclusions</h4>This study suggested a high prevalence of low vision and blindness in this study cohort. Uncorrected refractive error and cataract remain the leading cause of visual impairment, but the major challenge is the early diagnosis and intervention of diabetic retinopathy to reduce diabetes-related blindness.
Project description:<h4>Purpose</h4>To estimate and characterize the use of informal care by people with vision impairment in Portugal.<h4>Methods</h4>A total of 546 visually impaired individuals were recruited from Portuguese hospitals. Clinical information was obtained from medical records, socio-demographic details and informal care use were collected during face-to-face interviews. In addition, participants responded to a functional vision questionnaire (activity inventory) to assess their visual ability. Logistic regression was used to determine independent factors associated with informal care use and linear regression was used to determine independent predictors of intensity of informal care use.<h4>Results</h4>Informal care was reported by 39.6% of the participants. The probability of reporting informal care was higher in non-married, those with comorbidities, with lower visual ability and worse visual acuity. The median number of caregivers' hours per year was 390 (mean = 470; 95%CI = 488-407), which represent a median opportunity cost of €2,586. Visual ability was the only independent predictor of number of hours of informal care received.<h4>Conclusions</h4>Informal care was frequently used by individuals with impaired vision. Improving visual ability of people with impaired vision when performing valued activities may reduce the burden of visual loss at personal and societal level. This could be achieved with person-centred visual rehabilitation.
Project description:Visual impairment significantly alters the quality of life of people with Multiple Sclerosis (MS). The objective of this study was to identify predictors (independent variables) of visual outcomes, and to define their relationship with neurological disability and retinal atrophy when assessed by optical coherence tomography (OCT). We performed a cross-sectional analysis of 119 consecutive patients with MS, assessing vision using high contrast visual acuity (LogMar), 2.5% and 1.25% low contrast visual acuity (Sloan charts), and color vision (Hardy-Rand-Rittler plates). Quality of vision is a patient reported outcome based on an individual's unique perception of his or her vision and was assessed with the Visual Functioning Questionnaire-25 (VFQ-25) with the 10 neuro-ophthalmologic items. MS disability was assessed using the expanded disability status scale (EDSS), the MS functional composite (MSFC) and the brief repetitive battery-neuropsychology (BRB-N). Retinal atrophy was assessed using spectral domain OCT, measuring the thickness of the peripapillar retinal nerve fiber layer (pRNFL) and the volume of the ganglion cell plus inner plexiform layer (GCIPL). The vision of patients with MS was impaired, particularly in eyes with prior optic neuritis. Retinal atrophy (pRNFL and GCIPL) was closely associated with impaired low contrast vision and color vision, whereas the volume of the GCIPL showed a trend (p = 0.092) to be associated with quality of vision. Multiple regression analysis revealed that EDSS was an explanatory variable for high contrast vision after stepwise analysis, GCIPL volume for low contrast vision, and GCIPL volume and EDSS for color vision. The explanatory variables for quality of vision were high contrast vision and color vision. In summary, quality of vision in MS depends on the impairment of high contrast visual acuity and color vision due to the disease.