Serum beta carotene, alpha tocopherol, and age-related maculopathy: the Blue Mountains Eye Study

Systemic and ocular fluid compounds as potential biomarkers in age-related macular degeneration

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

Age-Related Macular Degeneration: Advances in Management and Diagnosis

Age-related macular degeneration (AMD) is the most common cause of irreversible visual impairment in older populations in industrialized nations. AMD is a late-onset deterioration of photoreceptors and retinal pigment epithelium in the central retina caused by various environmental and genetic factors. Great strides in our understanding of AMD pathogenesis have been made in the past several decades, which have translated into revolutionary therapeutic agents in recent years. In this review, we describe the clinical and pathologic features of AMD and present an overview of current diagnosis and treatment strategies.

Excessive retinol intake exacerbates choroidal neovascularization through upregulated vascular endothelial growth factor in retinal pigment epithelium in mice

As a part of the visual cycle, all-trans-retinol (all-trans-ROL), the major form of vitamin A in circulating blood, is transported to the retinal pigment epithelium (RPE). All-trans-ROL is essential for normal retina function. However, recent researches have shown that excessive retinol intake can cause increase of all-trans-retinal. This can lead to the accumulation of lipofuscin, which is important in the pathogenesis of retina degeneration disease, such as dry type age-related macular degeneration (AMD). Since there are few reports regarding the involvement of all-trans-ROL in exudative AMD, we investigated the effects of all-trans-ROL in vitro and in vivo. We evaluated vascular endothelial growth factor (VEGF) expression in ARPE-19 cells and THP-1 cells after all-trans-ROL treatment using ELISA and real-time RT-PCR. In-vitro tube formation assay was performed with HUVEC cells using the conditioned medium (CM) obtained from ARPE-19 cells treated with all-trans-ROL. Transcriptional activity of retinoic acid receptor (RAR) was evaluated using luciferase assay. In mice, VEGF expressions were investigated in the retina and RPE/choroid after three weeks of excessive oral retinol intake. Laser-induced choroidal neovascularization (CNV) models were evaluated after they were fed with various doses of retinol. VEGF mRNA expression and VEGF production were significantly increased in all-trans-ROL treated ARPE-19 cells, which were inhibited by an RAR antagonist LE540. In contrast, there were no significant changes in VEGF production in THP-1 cells. Transcriptional activity of RAR was upregulated by all-trans-ROL treatment in ARPE-19 cells. The CM, obtained from ARPE-19 cells treated with all-trans-ROL, induced more capillary-like tube formation than cells treated with control vehicles. In vivo, the high retinol diet group has increased VEGF expression in the RPE/choroid and larger lesion size was induced. Our results suggest that all-trans-ROL is a pro-angiogenic factor. Excessive retinoid intake may be a potential risk factor for exudative AMD.

Diminishing risk for age-related macular degeneration with nutrition: a current view

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. Clinical hallmarks of AMD are observed in one third of the elderly in industrialized countries. Preventative interventions through dietary modification are attractive strategies, because they are more affordable than clinical therapies, do not require specialists for administration and many studies suggest a benefit of micro- and macro-nutrients with respect to AMD with few, if any, adverse effects. The goal of this review is to provide information from recent literature on the value of various nutrients, particularly omega-3 fatty acids, lower glycemic index diets and, perhaps, some carotenoids, with regard to diminishing risk for onset or progression of AMD. Results from the upcoming Age-Related Eye Disease Study (AREDS) II intervention trial should be particularly informative.

Nutritional modulation of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly worldwide. It affects 30-50 million individuals and clinical hallmarks of AMD are observed in at least one third of persons over the age of 75 in industrialized countries (Gehrs et al., 2006). Costs associated with AMD are in excess of $340 billion US (American-Health-Assistance-Foundation, 2012). The majority of AMD patients in the United States are not eligible for clinical treatments (Biarnes et al., 2011; Klein et al., 2011). Preventive interventions through dietary modulation are attractive strategies because many studies suggest a benefit of micro- and macronutrients with respect to AMD, as well as other age-related debilities, and with few, if any, adverse effects (Chiu, 2011). Preservation of vision would enhance quality of life for millions of elderly people, and alleviate the personal and public health financial burden of AMD (Frick et al., 2007; Wood et al., 2011). Observational studies indicate that maintaining adequate levels of omega-3 fatty acids (i.e. with 2 servings/week of fish) or a low glycemic index diet may be particularly beneficial for early AMD and that higher levels of carotenoids may be protective, most probably, against neovascular AMD. Intervention trials are needed to better understand the full effect of these nutrients and/or combinations of nutrients on retinal health. Analyses that describe effects of a nutrient on onset and/or progress of AMD are valuable because they indicate the value of a nutrient to arrest AMD at the early stages. This comprehensive summary provides essential information about the value of nutrients with regard to diminishing risk for onset or progress of AMD and can serve as a guide until data from ongoing intervention trials are available.

Genetics of age-related macular degeneration: current concepts, future directions

Age-related macular degeneration (AMD) is a progressive degenerative disease which leads to blindness, affecting the quality of life of millions of Americans. More than 1.75 million individuals in the United States are affected by the advanced form of AMD. The etiological pathway of AMD is not yet fully understood, but there is a clear genetic influence on disease risk. To date, the 1q32 (CFH) and 10q26 (PLEKHA1/ARMS2/HTRA1) loci are the most strongly associated with disease; however, the variation in these genomic regions alone is unable to predict disease development with high accuracy. Therefore, current genetic studies are aimed at identifying new genes associated with AMD and their modifiers, with the goal of discovering diagnostic or prognostic biomarkers. Moreover, these studies provide the foundation for further investigation into the pathophysiology of AMD by utilizing a systems-biology-based approach to elucidate underlying mechanistic pathways.

Risk factors for age-related maculopathy

Age-related maculopathy (ARM) is the leading cause of blindness in the elderly. Although beneficial therapeutic strategies have recently begun to emerge, much remains unclear regarding the etiopathogenesis of this disorder. Epidemiologic studies have enhanced our understanding of ARM, but the data, often conflicting, has led to difficulties with drawing firm conclusions with respect to risk for this condition. As a consequence, we saw a need to assimilate the published findings with respect to risk factors for ARM, through a review of the literature appraising results from published cross-sectional studies, prospective cohort studies, case series, and case control studies investigating risk for this condition. Our review shows that, to date, and across a spectrum of epidemiologic study designs, only age, cigarette smoking, and family history of ARM have been consistently demonstrated to represent risk for this condition. In addition, genetic studies have recently implicated many genes in the pathogenesis of age-related maculopathy, including Complement Factor H, PLEKHA 1, and LOC387715/HTRA1, demonstrating that environmental and genetic factors are important for the development of ARM suggesting that gene-environment interaction plays an important role in the pathogenesis of this condition.

Dietary Antioxidants and the Long-term Incidence of Age-Related Macular Degeneration

PURPOSE

To assess the relationship between baseline dietary and supplement intakes of antioxidants and the long-term risk of incident age-related macular degeneration (AMD).

DESIGN

Australian population-based cohort study.

PARTICIPANTS

Of 3654 baseline (1992-1994) participants initially 49 years of older, 2454 were reexamined after 5 years, 10 years, or both.

METHODS

Stereoscopic retinal photographs were graded using the Wisconsin Grading System. Data on potential risk factors were collected. Energy-adjusted intakes of alpha-carotene; beta-carotene; beta-cryptoxanthin; lutein and zeaxanthin; lycopene; vitamins A, C, and E; and iron and zinc were the study factors. Discrete logistic models assessed AMD risk. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated after adjusting for age, gender, smoking, and other risk factors.

MAIN OUTCOME MEASURES

Incident early, late, and any AMD.

RESULTS

For dietary lutein and zeaxanthin, participants in the top tertile of intake had a reduced risk of incident neovascular AMD (RR, 0.35; 95% CI, 0.13-0.92), and those with above median intakes had a reduced risk of indistinct soft or reticular drusen (RR, 0.66; 95% CI, 0.48-0.92). For total zinc intake the RR comparing the top decile intake with the remaining population was 0.56 (95% CI, 0.32-0.97) for any AMD and 0.54 (95% CI, 0.30-0.97) for early AMD. The highest compared with the lowest tertile of total beta-carotene intake predicted incident neovascular AMD (RR, 2.68; 95% CI, 1.03-6.96; P = 0.029, for trend). Similarly, beta-carotene intake from diet alone predicted neovascular AMD (RR comparing tertile 3 with tertile 1, 2.40; 95% CI, 0.98-5.91; P = 0.027, for trend). This association was evident in both ever and never smokers. Higher intakes of total vitamin E predicted late AMD (RR compared with the lowest tertile, 2.83; 95% CI, 1.28-6.23; and RR, 2.55; 95% CI, 1.14-5.70 for the middle and highest tertiles, respectively; P = 0.22, for trend).

CONCLUSIONS

In this population-based cohort study, higher dietary lutein and zeaxanthin intake reduced the risk of long-term incident AMD. This study confirmed the Age-Related Eye Disease Study finding of protective influences from zinc against AMD. Higher beta-carotene intake was associated with an increased risk of AMD.

Macular pigment optical density in the elderly: findings in a large biracial Midsouth population sample

PURPOSE

To report the macular pigment optical density (MPOD) findings at 0.5 degrees of eccentricity from the fovea in elderly subjects participating in ARMA, a study of aging and age-related maculopathy (ARM) ancillary to the Health, Aging, and Body Composition (Health ABC) Study.

METHODS

MPOD was estimated with a heterochromatic flicker photometry (HFP) method in a large biracial population sample of normal 79.1 +/- 3.2-year-old adults living in the Midsouth (n = 222; 52% female; 23% black, 34% users of lutein-containing supplements). Within a modified testing protocol, subjects identified the lowest and the highest target intensity at which the flicker sensation disappeared, and the exact middle of this "no-flicker zone" was interpolated by the examiner.

RESULTS

An MPOD estimate was obtained successfully in 82% of the participants. The mean MPOD in our sample was 0.34 +/- 0.21 (SD). The interocular correlation was high (Pearson's r = 0.82). Compared with lutein supplement users, mean MPOD was 21% lower in nonusers (P = 0.013). MPOD was also 41% lower in blacks than in whites (P = 0.0002), even after adjustment for lutein supplement use. There were no differences in MPOD by gender, iris color, or history of smoking.

CONCLUSIONS

Older adults in the Midsouth appear to have average MPOD and interocular correlation comparable to those in previous studies. Lutein supplement use and white race correlated with higher MPOD. No evidence of an age-related decline in MPOD was seen in the sample. The HFP method for the measurement of MPOD is feasible in epidemiologic investigations of the elderly, the group at highest risk of ARM.

Macular pigment in the human retina: histological evaluation of localization and distribution

PURPOSE

Clinical investigations have demonstrated variation in both the peak optical density and the spatial distribution of macular pigment. To confirm these impressions histologically, the present study examined the distribution of macular pigment in the human retina.

MATERIALS AND METHODS

The macular retina of 11 donor eyes of different ages (28-91 years) were examined histologically on 100 microm vibratome sections directly, without further staining. Measurements were made in two dimensions: (1) adding the number of macular sections with visible macular pigment, and (2) direct measurement of the extension of macular pigment in the foveolar section, which visibly contained the most macular pigment.

RESULTS

The measurements with two methods demonstrated good correlation. The macula demonstrated a variation in the spatial extension of the visible macular pigment between 200 and 900 microm diameter around the centre of the fovea, which was also found when direct measurements were taken. There was no correlation with the donor age. The main location of macular pigment was in the layer of the fibres of Henle in the fovea and in the inner nuclear layer at the parafoveal site.

CONCLUSIONS

Histologically, a wide variation of the spatial distribution of macular pigment was found that confirms clinical observations. The primary localization of human macular pigment is in the inner retinal layers.

Nutritional antioxidants and age-related cataract and maculopathy

Loss of vision is the second greatest, next to death, fear among the elderly. Age-related cataract (ARC) and maculopathy (ARM) are two major causes of blindness worldwide. There are several important reasons to study relationships between risk for ARC/ARM and nutrition: (1) because it is likely that the same nutritional practices that are associated with prolonged eye function will also be associated with delayed age-related compromises to other organs, and perhaps, aging in general, (2) surgical resources are insufficient to provide economic and safe surgeries for cataract and do not provide a cure for ARM, and (3) there will be considerable financial savings and improvements in quality of life if health rather than old age is extended, particularly given the rapidly growing elderly segment of our population. It is clear that oxidative stress is associated with compromises to the lens and retina. Recent literature indicates that antioxidants may ameliorate the risk for ARC and ARM. Given the association between oxidative damage and age-related eye debilities, it is not surprising that over 70 studies have attempted to relate antioxidant intake to risk for ARC and ARM. This article will review epidemiological literature about ARC and ARM with emphasis on roles for vitamins C and E and carotenoids. Since glycation and glycoxidation are major molecular insults which involve an oxidative stress component, we also review new literature that relates dietary carbohydrate intake to risk for ARC and ARM. To evaluate dietary effects as a whole, several studies have tried to relate dietary patterns to risk for ARC. We will also give some attention to this emerging research. While data from the observational studies generally support a protective role for antioxidants in foods or supplements, results from intervention trials are less encouraging with respect to limiting risk for ARC/ARM prevalence or progress through antioxidant supplementations, or maintaining higher levels of antioxidants either in diet or blood. Without more information it is difficult to parse these results. It would be worthwhile to determine why the various types of studies are not yielding similar results. However, there are many common insults and mechanistic compromises that are associated with aging, and proper nutrition early in life may address some of these compromises and provide for extended youthful function later in life. Indeed, proper nutrition, possibly including use of antioxidant supplements for the nutritionally impoverished, along with healthy life styles may provide the least costly and most practical means to delay ARC and ARM. Further studies should be devoted to identifying the most effective strategy to prevent or delay the development and progress of ARC/ARM. The efforts should include identifying the right nutrient(s), defining useful levels of the nutrient(s), and determining the age when the supplementation should begin.

AMD and micronutrient antioxidants

Age-related maculopathy (ARM) is a common clinical entity. The late-stage manifestations of ARM, which are known as age-related macular degeneration (AMD), have devastating consequences for vision. Various risk factors have been identified in the development of the condition, which are consistent with the premise that oxidative stress plays an important role in its pathogenesis. Thus, the possibility that antioxidant balance can be manipulated through diet or supplementation has created much interest. Associations between diet and nutrition and the clinical features of ARM have been described. Scrutiny of the literature shows consistency in the report of notable reductions in serum micronutrients in wet AMD, however, the evidence for causation is still circumstantial. In this comprehensive review of the clinical literature, we have assessed the evidence for a link between diet and nutrition as risk factors for the development of ARM and AMD. All published case control, population-based, and interventional studies on ARM were examined. Although initial support appeared to be moderate and somewhat contradictory, the evidence that lifetime oxidative stress plays an important role in the development of ARM is now compelling. The positive outcomes in the Age-Related Eye Diseases Study, a major controlled clinical trial, have given hope that modulation of the antioxidant balance through supplementation can help prevent progression of ARM to AMD.

Epidemiology of age-related maculopathy: a review

Age-related maculopathy (ARM) is a degenerative disease of the retina and the leading cause of incurable blindness and visual impairment in industrialized countries. By definition, ARM is confined to the age-category above 50 years. The aetiology of ARM is still unknown, despite intensive research on many fronts. In this paper, we provide a review of the epidemiology of ARM. The most prominent findings were an exponential increase in frequency with age, a significant familial and genetic component, and a strong association with smoking. Other risk factors that were found less consistently were atherosclerosis, low intake of antioxidant nutrients, and cataract extraction. Future studies, both observational and experimental, will hopefully identify more risk factors that are amenable to prevention.

Biologic mechanisms of the protective role of lutein and zeaxanthin in the eye

The macular region of the primate retina is yellow in color due to the presence of the macular pigment, composed of two dietary xanthophylls, lutein and zeaxanthin, and another xanthophyll, meso-zeaxanthin. The latter is presumably formed from either lutein or zeaxanthin in the retina. By absorbing blue-light, the macular pigment protects the underlying photoreceptor cell layer from light damage, possibly initiated by the formation of reactive oxygen species during a photosensitized reaction. There is ample epidemiological evidence that the amount of macular pigment is inversely associated with the incidence of age-related macular degeneration, an irreversible process that is the major cause of blindness in the elderly. The macular pigment can be increased in primates by either increasing the intake of foods that are rich in lutein and zeaxanthin, such as dark-green leafy vegetables, or by supplementation with lutein or zeaxanthin. Although increasing the intake of lutein or zeaxanthin might prove to be protective against the development of age-related macular degeneration, a causative relationship has yet to be experimentally demonstrated.

Dietary Modification and Moderate Antioxidant Supplementation Differentially Affect Serum Carotenoids, Antioxidant Levels and Markers of Oxidative Stress in Older Humans

Oxidative stress is thought to be a factor in the progression of chronic diseases, and even the aging process itself. We examined the effect of two moderate vitamin, mineral and phytochemical supplements and a dietary intervention on markers of oxidative stress and antioxidant status in older humans. Subjects (n = 60, 65-85 y old) were enrolled in a 5-wk, double-blind, placebo-controlled study. The subjects were randomly assigned to a group with one of four interventions: antioxidant supplement capsule, antioxidant supplement tablet, high carotenoid diet or placebo. Postintervention serum levels of some of the supplemented carotenoids and alpha-tocopherol were higher in all treated groups compared with the placebo group and with preintervention levels within groups. Markers of oxidative stress or antioxidant capacity were not significantly different from preintervention levels, although the diet and supplement capsule groups had lower levels of some of those markers than the placebo group postintervention. The results suggest that both moderate antioxidant supplementation and a diet high in carotenoids elevate serum carotenoids and antioxidant levels in an older adult population, although with different specific effects.

Changes in blood antioxidants and several lipid peroxidation products in women with age-related macular degeneration

PURPOSE

The aim of this study was to evaluate the ferric reducing ability of plasma (FRAP), selected enzymatic and non-enzymatic components of the antioxidative system, and the intensity of peroxidative processes in the blood of patients with age-related macular degeneration (AMD).

METHODS

In the peripheral blood, we evaluated FRAP; concentrations of vitamins C, A, and E; and of thiols. We assayed the activity of enzymatic components of the antioxidative system-superoxide dismutase, catalase, ceruloplasmin and the concentration of reduced glutathione as an indicator of glutathione peroxidase activity. In order to determine the intensity of lipid peroxidation, we measured the concentrations of malondialdehyde and hydroxyalkenales (MDA-HNA) and conjugated diens (CD).

RESULTS

We found a significant increase in FRAP in patients with AMD compared with the control group. The average concentrations of vitamins A and C were low and vitamins E and GSH were significantly higher in AMD than in the control group. The activity of almost all the antioxidative enzymes was high. We found a significant increase in MDA-HNA but no difference in CD.

CONCLUSIONS

The significantly higher concentration of lipid peroxidation products in patients with AMD indicates an important pathogenic role of oxido-reduction disturbance. The high FRAP concentration may be one of the protective mechanisms in oxidation stress. The adaptive increase of the antioxidant barrier mostly involves the enzymatic components.

Age-related macular degeneration: epidemiology and optimal treatment

Age-related macular degeneration (AMD) is a common macular disease affecting elderly people in the Western world. It is characterised by the appearance of drusen in the macula, accompanied by choroidal neovascularisation (CNV) or geographic atrophy. The disease is more common in Caucasian individuals than in pigmented races. In predominantly Caucasian populations, the age-standardised prevalence of AMD in at least one eye is 7760 cases per million. The age-standardised cumulated 1-year incidence of AMD in at least one eye is 1051 cases per million individuals. AMD is the most important single cause of blindness among Caucasian individuals in developed countries. Blindness resulting from AMD rarely occurs before age 70, and most cases occur after age 80. The age-standardised 1-year incidence of legal blindness resulting from AMD is 212 cases per million. Two-thirds of AMD cases have CNV (exudative cases); the remainder has only geographic atrophy. In cross-sectional population-based studies about 45% of eyes with AMD have visual acuity reduced to 20/200 or worse. This is true both for exudative AMD and pure geographic atrophy. Age and genetic predisposition are known risk factors for AMD. Smoking is probably also a risk factor. Preventive strategies using macular laser photocoagulation are under investigation, but their efficacy in preventing visual loss is as yet unproven. There is no treatment with proven efficacy for geographic atrophy. Optimal treatment for exudative AMD requires a fluorescein angiographic study and a physician capable of interpreting it. For CNV not involving the foveal centre, the only evidence-based treatment is laser photocoagulation. For AMD cases with subfoveal CNV, good visual acuity, and predominantly classic fluorescence pattern on fluorescein angiography, photodynamic therapy with verteporfin is the treatment of choice. Photodynamic therapy is also effective in eyes with pure occult CNV and evidence of recent disease progression. For new subfoveal CNV with poor vision and recurrent CNV, laser photocoagulation can be considered.

Serum oxidative and antioxidant parameters in a group of Italian patients with age-related maculopathy

OBJECTIVES

The purpose of this study was to measure the oxidative and antioxidant biochemical parameters in the serum of Italian patients with age-related maculopathy (ARM) and in a similar age control group from the same area, in order to determine the weight of oxidative status as risk factor in the early stage of macular degeneration onwards.

DESIGN AND METHODS

Forty-eight ARM patients (19 early and 29 late form) and 46 normal subjects, similar for age, sex and life-style, were studied. A series of serum and/or plasma antioxidants (vitamins C, E, A, total and individual carotenoids, zinc, total plasma antioxidant capacity--TRAP) and oxidative parameters (reactive oxygen metabolites--ROM, oxidized-low-density lipoprotein antibodies-anti-Ox-LDL) were evaluated in both groups, also with regard to age and disease stage.

RESULTS

Levels of vitamins C, E, total carotenoids and beta-cryptoxanthine were lower in late ARM than in early ARM (p<0.05). Of the serum carotenoids investigated, only lycopene was lower in the two ARM forms than in controls (p<0.05). The main biochemical parameters, TRAP, zinc, anti-Ox-LDL and ROM were similar in the two groups.

CONCLUSIONS

A deficit of antioxidants (vitamins C, E and carotenoids) seems to be associated with ARM in Italian patients, particularly the advanced form, it is also suggested that in ARM patients macular susceptibility to oxidative damage is not related with age.

The role of oxidative stress in the pathogenesis of age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blind registration in the developed world, and yet its pathogenesis remains poorly understood. Oxidative stress, which refers to cellular damage caused by reactive oxygen intermediates (ROI), has been implicated in many disease processes, especially age-related disorders. ROIs include free radicals, hydrogen peroxide, and singlet oxygen, and they are often the byproducts of oxygen metabolism. The retina is particularly susceptible to oxidative stress because of its high consumption of oxygen, its high proportion of polyunsaturated fatty acids, and its exposure to visible light. In vitro studies have consistently shown that photochemical retinal injury is attributable to oxidative stress and that the antioxidant vitamins A, C, and E protect against this type of injury. Furthermore, there is strong evidence suggesting that lipofuscin is derived, at least in part, from oxidatively damaged photoreceptor outer segments and that it is itself a photoreactive substance. However, the relationships between dietary and serum levels of the antioxidant vitamins and age-related macular disease are less clear, although a protective effect of high plasma concentrations of alpha-tocopherol has been convincingly demonstrated. Macular pigment is also believed to limit retinal oxidative damage by absorbing incoming blue light and/or quenching ROIs. Many putative risk-factors for AMD have been linked to a lack of macular pigment, including female gender, lens density, tobacco use, light iris color, and reduced visual sensitivity. Moreover, the Eye Disease Case-Control Study found that high plasma levels of lutein and zeaxanthin were associated with reduced risk of neovascular AMD. The concept that AMD can be attributed to cumulative oxidative stress is enticing, but remains unproven. With a view to reducing oxidative damage, the effect of nutritional antioxidant supplements on the onset and natural course of age-related macular disease is currently being evaluated.

Treatment of age-related macular degeneration

Age-related macular degeneration (AMD), while rapidly becoming more prevalent due to an aging population, is still poorly understood and treatment modalities are limited. Fortunately, advances are being made in the treatment of AMD that may greatly alter the outcome of this debilitating disease. Treatments for both wet and dry AMD are reviewed.

Nutrition and the eye

The topic "nutrition and the eye" cannot adequately be covered in a single review article; indeed, dozens of books and hundreds of articles have been written on the subject. This review concentrates on three areas in which specific nutrients are known or theorized to have a major impact on vision and the visual system: vitamin A deficiency; antioxidants and their proposed role in the prevention of age-related cataract and macular degeneration; and nutritional optic neuropathies, including those of the recent Cuban epidemic. In addition, this article touches on nutritional treatments that have been suggested for several less common eye diseases and, finally, considers several less prevalent conditions in which deficiency of or excess exposure to a particular nutrient has been associated with ocular pathology.

Dietary carotenoids and certain cancers, heart disease, and age-related macular degeneration: a review of recent research

Key epidemiologic studies show associations between high dietary intakes of certain carotenoid-containing fruits and vegetables and reduced risk of prostate cancer, breast cancer, head and neck cancers, cardiovascular disease, and age-related macular degeneration, although overall the evidence is inconsistent. Little is known about the potential biochemical mechanisms whereby carotenoids might protect against disease, and human intervention trials are limited to high dose beta-carotene, which is not protective against lung cancer or cardiovascular disease. Authoritative scientific organizations continue to emphasize increased consumption of fruits and vegetables but do not make specific recommendations for carotenoids because of a lack of data that directly link them to disease reduction.

Choroidal neovascularization in younger patients

Choroidal neovascularization (CNV) is the most common cause of legal blindness in older adults in the United States. The most common cause for CNV in this age group is age-related macular degeneration, a condition manifesting with drusen (particularly soft drusen) and pigmentary alterations in the macular region. CNV can occur in younger people (< 50 years), who usually do not have conspicuous drusen or pigmentary abnormalities. In this age group CNV may occur as a secondary manifestation of many inherited and acquired conditions such as angioid streaks, high myopia, trauma, choroidal tumors, familial macular dystrophies, and inflammatory retinochoroidopathies. Occasionally, CNV in young people has no apparent antecedent cause, and these cases are termed "idiopathic CNV." This review examines the common reasons for CNV in young adults, with reference to some of the older literature as well as to recently published papers.

Antioxidant vitamins and age-related eye disease

Basic research studies suggest that oxidative mechanisms may play an important role in the pathogenesis of cataract and age-related macular degeneration, the two most important causes of visual impairment in older adults. These findings raise the possibility that vitamins and trace minerals with antioxidant properties can be of benefit in preventing the onset or progression of disabling eye disease. Results from observational epidemiological studies in humans, however, are inconclusive. Although findings from several studies, primarily cross-sectional and case-control, are generally compatible with a possible protective role for micronutrients in disease development, the data for specific nutrients or specific disease types are inconsistent. The imprecision of dietary exposure data and the likely effects of uncontrolled confounding further limit these observational studies. Well-designed, large-scale, randomized trials are required to evaluate definitively the potentially important benefit of vitamin supplementation in eye disease.