Incidence of myopia in Swedish schoolchildren: A longitudinal study.

PURPOSE: The prevalence of myopia in Scandinavia tends to be lower than in other parts of the world. This study aimed to investigate the incidence of myopia and its predictors in Swedish children to characterise this trend. METHODS: A 2-year longitudinal study was conducted following a cohort of schoolchildren aged 8-16 years. Myopia was defined as a spherical equivalent refraction (SER) ≤ -0.50 D. The study enrolled 128 participants, 70 (55%) females with a mean age of 12.0 years (SD = 2.4). RESULTS: The cumulative incidence of myopia during the follow-up period was 5.5%, and the incidence rate of myopia was 3.2 cases per 100 person-years. Participants with myopia at baseline exhibited a faster increase in refractive error during the follow-up period. Likewise, participants with two myopic parents exhibited a more marked change towards myopia, regardless of their initial refractive error. CONCLUSION: In the current study, similar to prevalence, the incidence of myopia was low when compared with other parts of the world. These results lead us to formulate a new hypothesis that the normal emmetropisation process may be protected by low educational pressure practised in Sweden during early childhood. Further research is necessary to test this new hypothesis.

Predictors of problems reported on the EQ-5D-3L dimensions among people with impaired vision in northern Portugal.

BACKGROUND: The EQ-5D index often fails to detect the effect of ophthalmic diseases and sight loss. Investigating predictors of individual EQ-5D health dimensions might reveal the underlying reasons. The aim of this study was to investigate predictors of health dimension ratings obtained with the EQ-5D-3L from participants with impaired vision representing a spectrum of eye diseases. METHODS: Observational cross-sectional study with participants recruited at four public hospitals in Portugal. Outpatients with visual acuity of 0.30 logMAR(6/12) or worse in the better-seeing eye were invited to participate. Participants completed two instruments: the EQ-5D-3L (measures participants' perceived health-related quality-of-life) and the Massof Activity Inventory (measures visual ability-ability to perform vision-related activities). This study used logistic regression models to identify factors associated with responses to the EQ-5D-3L. RESULTS: The study included 492 participants, mean age 63.4 years (range = 18-93), 50% females. The most common diagnosis was diabetic retinopathy (37%). The mean visual acuity in the better seeing eye was 0.65 logMAR (SD = 0.48) and the mean visual ability was 0.62 logits (SD = 2.04), the correlation between the two was r = - 0.511 (p < 0.001). Mobility and self-care were the health dimensions with the fewest problems (1% reported extreme problems), anxiety and depression the dimension with the most problems (24% reported extreme problems). ROC curve analysis showed that the EQ-5D index was a poor predictor of cases of vision impairment whilst visual ability given was a good predictor of cases of vision impairment. Visual ability was an independent predictor of the response for all dimensions, higher ability was always associated with a reduced odds of reporting problems. The odds of reporting problems were increased for females in 3 out of 5 dimensions. Comorbidities, visual acuity and age-category were predictors of the odds of reporting problems for one dimension each. CONCLUSIONS: The odds of reporting problems for the five health dimensions of the EQ-5D-3L were strongly influenced by the ability to perform vision-related activities (visual ability). The EQ-5D index showed poor performance at detecting vision impairment. These findings are informative and relevant for the clinic and for research evaluating the impact of eye diseases and disease treatments in ophthalmology.

Cross-sectional study investigating the prevalence and causes of vision impairment in Northwest Portugal using capture-recapture.

OBJECTIVES: The aim of this study was to estimate the prevalence and causes of vision impairment (VI) in Portugal. SETTING: Information about people with VI was obtained from primary care centres, blind association (ACAPO) and from hospitals (the PCVIP study) in the Northwest of Portugal during a period spanning years 2014-2015. Causes of VI were obtained from hospitals. PARTICIPANTS: Administrative and medical records of people with visual acuity in the better seeing eye of 0.5 decimal (0.30logMAR) or worse and/or visual field less than 20° were investigated. Capture-recapture with log-linear models was applied to estimate the number of individuals missing from lists of cases obtained from available sources. PRIMARY AND SECONDARY OUTCOME MEASURES: Log-linear models were used to estimate the crude prevalence and the category specific prevalence of VI. RESULTS: Crude prevalence of VI was 1.97% (95% CI 1.56% to 2.54%), and standardised prevalence was 1% (95% CI 0.78% to 1.27%). The age-specific prevalence was 3.27% (95% CI 2.36% to 4.90%), older than 64 years, 0.64% (95% CI 0.49% to 0.88%), aged 25-64 years, and 0.07% (95% CI 0.045% to 0.13%), aged less than 25 years. The female-to-male ratio was 1.3, that is, higher prevalence among females. The five leading causes of VI were diabetic retinopathy, cataract, age-related macular degeneration, glaucoma and disorders of the globe. CONCLUSIONS: The prevalence of VI in Portugal was within the expected range and in line with other European countries. A significant number of cases of VI might be due to preventable cases and, therefore, a reduction of the prevalence of VI in Portugal seems possible. Women and old people were more likely to have VI and, therefore, these groups require extra attention. Future studies are necessary to characterise temporal changes in prevalence of VI in Portugal.

A Review of Capture-recapture Methods and Its Possibilities in Ophthalmology and Vision Sciences.

Epidemiological information is expected to be used to develop key aspects of eye care such as to control and minimise the impact of diseases, to allocate resources, to monitor public health actions, to determine the best treatment options and to forecast the consequence of diseases in populations. Epidemiological studies are expected to provide information about the prevalence and/or incidence of eye diseases or conditions. To determine prevalence is necessary to perform a cross-sectional screening of the population at risk to ascertain the number of cases. The aim of this review is to describe and evaluate capture-recapture methods (or models) to ascertaining the number of individuals with a disease (e.g. diabetic retinopathy) or condition (e.g. vision impairment) in the population. The review covers the fundamental aspects of capture-recapture methods that would enable non-experts in epidemiology to use it in ophthalmic studies. The review provides information about theoretical aspects of the method with examples of studies in ophthalmology in which it has been used. We also provide a problem/solution approach for limitations arising from the lists obtained from registers or other reliable sources. We concluded that capture-recapture models can be considered reliable to estimate the total number of cases with eye conditions using incomplete information from registers. Accordingly, the method may be used to maintain updated epidemiological information about eye conditions helping to tackle the lack of surveillance information in many regions of the globe.

Cost-effectiveness of basic vision rehabilitation (The basic VRS-effect study): study protocol for a randomised controlled trial.

PURPOSE: To investigate the cost-effectiveness of a basic vision rehabilitation service (basic-VRS) in Portugal. We designed a parallel group, randomised controlled trial whose aim is to compare the effects and costs of 'usual low vision care' with a 'basic-VRS intervention' on self-reported visual ability and other psychosocial and health-related quality-of-life outcomes. METHODS: The trial will recruit participants that meet the following inclusion criteria: (1) visual acuity between 0.4-1.0 logMAR in the better-seeing eye, (2) cause of vision loss is diabetic retinopathy or age-related macular degeneration, (3) 18 years or older and iv) live in the community (not in nursing homes or other type of institution). Participants will be randomised to one of the study arms consisting of immediate intervention and delayed intervention. The delayed intervention group will receive 'usual care' or no intervention in the first 12 weeks. Visual acuity, contrast sensitivity and retinal structure will be assessed during the study. RESULTS: The primary outcome measure is visual ability, which will be evaluated with the Massof Activity Inventory, we expect that the intervention will raise the overall person measure or visual ability. Reading, health-related quality-of-life, anxiety and depression and social support will be also assessed. The analysis will be undertaken on an intention-to-treat basis. A cost-effectiveness analysis will be performed to provide information about the cost per unit of utility. To evaluate the cost-effectiveness of the intervention we will adopt the perspective of the healthcare system. CONCLUSION: This study will provide additional evidence about the effects of basic-VRS on self-reported visual ability. Findings from this study should also contribute to better planning of low vision provision and, consequently, may contribute to reduce barriers to basic-VRS.

Predicting participation of people with impaired vision in epidemiological studies.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

The use of informal care by people with vision impairment.

PURPOSE: To estimate and characterize the use of informal care by people with vision impairment in Portugal. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Visual and health outcomes, measured with the activity inventory and the EQ-5D, in visual impairment.

PURPOSE: Generic instruments to assess health utilities can be used to express the burden of health problems in widely used indexes. That is in contrast with what can be obtained with condition-specific instruments, outcomes are very specific and difficult to compare across conditions. The purpose of this study was to assess health and visual outcomes and its determinants in patients with visual impairment (VI) using the EQ-5D-3L and the Activity Inventory (AI). METHODS: Participants were recruited in different hospitals during the PCVIP-study. A total of 134 patients with acuity 0.30 logMAR or less in the better eye were interviewed. The AI includes 46 goals split between three objectives: social functioning, recreation and daily living, and was used to measure visual ability. The EQ-5D consists of five questions covering one domain each and was used to provide a measure of health states. Responses to each domain were combined to produce a single individual index. RESULTS: The AI and the EQ-5D-3L showed enough discriminatory power between VI levels (p < 0.001), and their results were strongly correlated r(134) = 0.825, (p < 0.001). Explanatory factors for visual ability were level of VI in better eye, age and gender, R2  = 0.43, (p < 0.001). Explanatory factors for the EQ-5D-3L were level of VI in the better eye, comorbidities and gender, R2  = 0.36, (p < 0.001). CONCLUSION: Our results showed that the EQ-5D-3L is useful when characterizing the burden of VI and to compute, when necessary, quality-adjusted-life-years (QALY) changes due to VI. However, it is important to consider that the EQ-5D-3L uses a coarse response scale, assesses a limited spectrum of domains and is influenced by comorbidities. This might limit its responsiveness to small changes in visual ability.