Dr Laura Downie
BOptom PhD(Melb) PGCertOcTher FAAO FACO DipMus(Prac) AMusA
Lecturer and NHMRC TRIP Fellow, Department of Optometry & Vision Sciences, Faculty of Medicine, Dentistry & Health Sciences, The University of Melbourne
Association between self-reported calcium supplement consumption and AMD
Self-reported calcium supplement consumption has been shown to be associated with an increased prevalence of AMD. A cross-sectional study involved 3,191 participants, aged at least 40 years, in the 2007-2008 National Health and Nutrition Examination Survey. Participants were interviewed regarding dietary supplement and antacid use during the 30-day period preceding enrolment.
The presence or absence of AMD was determined by retinal fundus photography. Multivariable logistic regression models were used to determine the odds of an AMD diagnosis among participants who self-reported calcium consumption versus those not self-reporting supplementary calcium consumption, after adjusting for confounders.
A total of 248 participants (7.8 per cent) were diagnosed with AMD. After adjusting for potential confounders, participants who self-reported consuming more than 800 mg/day of supplementary calcium were found to have relatively higher odds of an AMD diagnosis (OR 1.85; 95% CI 1.25 to 2.75).
The association between self-reported supplementary calcium intake and AMD was stronger in older than younger participants (OR 2.63; 95% CI 1.52 to 4.54). A clear dose-response association between the quintiles of self-reported supplementary calcium intake and AMD was not established.
JAMA Ophthalmol; ePub 9 April 2015.
Misidentification of objects in people with AMD
Patients with AMD show impaired performance with identifying objects and scenes. This contrasts with previous studies that have shown that people with AMD can detect a predefined target object or scene with high accuracy.
In this study, photographs of isolated objects, natural scenes and objects in scenes were centrally displayed for two seconds each. Participants (n = 20 with AMD, n = 15 age-matched controls and n = 12 younger controls) were asked to name the stimuli.
Naming accuracy and the speed of naming were impaired in people with AMD, compared with age-matched controls, in the three categories of images. More than 20 per cent of the misidentifications resulted from a structural and/or semantic similarity between the object and the name (for example, spectacles for dog plates or dolphin for shark).
The authors reported that accuracy and naming times did not differ significantly between young and older normally-sighted participants, suggesting that the deficits in AMD patients were related to pathological changes rather than normal ageing.
It was concluded that these findings indicate that in AMD patients, peripheral vision may be adequate for object and scene detection, but not for precise scene or object identification.
Ophthalmic Physiol Opt; ePub 6 April 2015.
Smoking, antioxidant supplementation and diet in Australians with AMD
Adherence to smoking and dietary recommendations have been found to be relatively poor among older Australians with AMD, and the uptake of antioxidant supplements increases significantly among those with late-stage AMD.
A study undertaken in Sydney compared the micronutrient usage and other lifestyle behaviours of people with and without AMD, over a 10-year period. Participants (n = 1612) were aged at least 49 years at baseline. AMD status was assessed using retinal fundus photographs. Dietary data were collected using a semi-quantitative food frequency questionnaire. Smoking status was self-reported.
At baseline, 56 people had AMD; of these, 25 per cent ceased smoking at five years and were still not smoking at the 10-year follow-up. Among participants who had below the recommended intake of vitamins A, C or E supplements at baseline, those who did compared to those who did not develop late AMD over 10 years were more likely to report vitamins A (total), C or E supplement intake above the recommended intake at the 10-year follow-up: multivariable-adjusted OR 4.21 (95% CI 1.65 to 10.73); OR 6.52 (95% CI 2.76 to 15.41); and OR 5.71 (95% CI 2.42 to 13.51), respectively.
Compared to those participants without AMD at baseline, those with AMD did not significantly increase their intake of fish, fruit or vegetables or change their overall diet quality over the 10-year follow-up period.
PLoS One 2015; 10: 3: e0122548.
Visual function losses in early AMD
Eyes in the earliest stages of AMD, where visual acuity and contrast sensitivity are not yet impaired, show significantly delayed rod-mediated dark adaptation compared with age-matched eyes with normal macular health.
Adults (n = 640) aged 60 years or older had their macular health assessed using colour stereographic retinal fundus photographs by an experienced grader. Each eye was classified as having either normal macular health or early stages of AMD (grades 2 to 4 using the nine-step AREDS classification system for AMD severity). Visual function was assessed using best-corrected visual acuity (VA), low luminance VA, contrast sensitivity, macular cone-mediated light sensitivity and rod-mediated dark adaptation.
A total of 1,260 eyes were tested (n = 1,007 with normal macular health, n = 253 with early AMD). Following adjustment for age and gender, early AMD eyes had twice the odds of having delayed rod-mediated dark adaptation than eyes with normal macular health. Visual acuity, low luminance visual acuity, contrast sensitivity and macular light sensitivity did not differ between early AMD eyes and those with normal macular health.
Curr Eye Res 2015; 24: 1-7.
AMD in patients with AIDS
Patients with acquired immuno-deficiency syndrome (AIDS) have an increased, age-adjusted prevalence of intermediate-stage AMD compared with non-HIV-infected individuals. This finding is consistent with a higher prevalence of other age-related diseases in antiretroviral-treated, immune-restored, HIV-infected persons compared with non-HIV-infected persons.
The findings were from a cross-sectional study of AIDS patients (n = 1825) who were enrolled in the Longitudinal Study of the Ocular Complications of AIDS in the United States. Retinal photographs were taken of each participant at enrolment; masked graders identified participants with intermediate-stage AMD.
Almost 10 per cent of participants had intermediate-stage AMD. The prevalence of AMD ranged from four per cent of participants 30-39 years old to 24.3 per cent of participants aged at least 60 years. Other risk factors for AMD included the HIV risk groups of injection drug use (OR 2.4, 95% CI 1.5 to 3.9) or heterosexual contact (OR 1.9, 95% CI 1.3 to 2.8).
Compared with an HIV-uninfected population in the Beaver Dam Offspring Study, there was an approximate four-fold increase in age-adjusted prevalence of intermediate-stage AMD in this population of AIDS patients.
Am J Ophthalmol; Epub 11 March 2015.
Reticular pseudodrusen associated with a diseased Bruch’s membrane in pseudoxanthoma elasticum
Reticular pseudodrusen (RPD) are most commonly associated with AMD and are recognised as an independent risk factor for disease progression. This study reports a high prevalence of RPD in eyes of younger patients with pseudoxanthoma elasticum (PXE).
The single-centre, prospective, cross-sectional case series sought to describe the prevalence, phenotype and topographic distribution of RPD, as well as the association of RPD with diseased Bruch’s membrane, in patients with PXE.
Patients with PXE (n = 57) were evaluated with multiple retinal imaging modalities. A sub-group (n = 15) was excluded due to the presence of large central fibrosis or atrophy. RPD were detected in 22 of the remaining 42 patients with PXE (52%; 95% CI, 38 to 67%). The prevalence of RPD was highest in the fifth decade.
The authors concluded that the association of RPD with a diseased Bruch’s membrane in PXE suggests a pathogenic role for changes in this anatomical structure in the development of RPD.
JAMA Ophthalmol; Epub 12 March 2015.
Association between neovascular AMD and dementia
A population-based, case-control study in Taiwan has reported an association between neovascular AMD and dementia.
Data for the study were retrospectively collected from the Taiwan National Health Insurance Research Database. Two populations were analysed: people with a diagnosis of dementia (n = 13,402) and those without dementia (controls, n = 40,206). A conditional logistic regression was used to examine the association of dementia with previously diagnosed neovascular AMD.
In the patient groups with dementia and the controls, 1.35 per cent and 0.90 per cent had been previously diagnosed with neovascular AMD, respectively (p < 0.001). Conditional logistic regression analysis suggested that the odds ratio for prior neovascular AMD for people with dementia was 1.37 (95% CI 1.14 to 1.65) compared with controls, after adjusting for potential confounding factors.
PLoS One 2015; 6: 10: 3: e0120003.
Serum leptin and AMD
Leptin is an amino acid protein that is secreted by adipocytes. It has been shown in a study to reduce beta-amyloid deposition and intracellular lipid concentration in animal models, which are two key pathogenic mechanisms that occur with ageing.
The aim of the study was to examine the association between serum leptin levels and AMD. The population-based, case-control study included Chinese and Indian adults aged 40 to 80 years, who participated in the Singapore Epidemiology of Eye Diseases Study (2007–2011). AMD was assessed using graded retinal photographs, performed using a modified Wisconsin Age-Related Maculopathy Grading System (n = 426; early AMD, n = 389, late AMD, n = 37). Controls (n = 927) showed no signs of AMD and were matched for age, sex and ethnicity. Serum leptin levels were measured using an enzyme-linked immunosorbent assay (ELISA) kit.
Compared with controls, participants with AMD had lower levels of serum leptin (mean [sd]: 10.0 [11.5] ng/mL versus 12.9 [16.4] ng/mL; p = 0.001). The mean levels of serum leptin among those with late, early and without AMD were 8.8, 10.1, and 12.9 ng/mL, respectively (p trend = 0.005). In multivariable models adjusting for potential confounders, increasing quartiles of leptin were associated with lower odds of AMD (OR 0.56, 95% CI 0.35 to 0.92) comparing highest to lowest quartile of serum leptin.
Higher serum leptin levels were inversely associated with AMD. These findings, if confirmed in prospective studies, may provide insights into new pathogenic pathways and possibly therapeutic targets in AMD.
Invest Ophthalmol Vis Sci 2014; 56: 3: 1880-1886.