Macular and Plasma Xanthophylls Are Higher in Age-related Macular Degeneration than in Normal Aging: Alabama Study on Early Age-related Macular Degeneration 2 Baseline

An Overview on the Effects of Some Carotenoids on Health: Lutein and Zeaxanthin

PURPOSE OF REVIEW

In this review, the chemical properties, nutritional sources, absorption mechanisms, metabolism, biosynthesis and promising health-related benefits of lutein and zeaxanthin were emphasized and some recommendations for the future studies are suggested.

RECENT FINDINGS

Lutein and zeaxanthin are phytochemical compounds in the carotenoid group and are synthesised only by plants. All mammals get lutein and zeaxanthin into their bodies by consuming plant-based foods. Especially leafy green vegetables, broccoli, pumpkin, cabbage, spinach and egg yolk are rich in lutein and zeaxanthin. Lutein and zeaxanthin have potential health effects by preventing free radical formation, exhibiting protective properties against oxidative damage and reducing oxidative stress. These compounds have neuroprotective, cardioprotective, ophthalmological, antioxidant, anti-inflammatory, anti-cancer, anti-osteoporosis, anti-diabetic, anti-obesity, and antimicrobial effects. The preventive properties of lutein and zeaxanthin against numerous diseases have attracted attention recently. Further clinical trials with large samples are needed to make generalisations in the prevention and treatment of diseases and to determine the appropriate doses and forms of lutein and zeaxanthin.

In Vivo Correlation Between Macular Pigment Optical Volume and Retinal Layers Thickness

Purpose

This study aims to investigate the potential in vivo relationship between macular pigment (MP) and retinal layers thickness in healthy subjects and dry, non-advanced age-related macular degeneration (AMD).

Methods

An observational, cross-sectional study was conducted. Healthy subjects >40 years and patients with early or intermediate AMD were recruited. Structural OCT and macular pigment optical volume (MPOV) were collected for each subject. Retinal layers parameters were calculated based on the standard early treatment diabetic retinopathy study (ETDRS) map. Additionally, MPOV within 1°, 2°, and 9° of eccentricity was assessed and associated with retinal layers thickness and volume. Linear mixed-effects models were used to test the relationship between MP and structural OCT parameters, while adjusting for known possible confounding factors.

Results

A total of 144 eyes of 91 subjects (60.4% females) were evaluated, comprising 43% normal eyes and 57% with early/intermediate AMD. Among the retinal layers, only the outer nuclear layer (ONL) thickness and volume appeared to be associated to higher MP levels. Specifically, the central ONL thickness was identified as a significant predictor of the MPOV 1°(P = 0.04), while the parafoveal ONL thickness (inner ETDRS subfield) was identified as a significant fixed effect on the MPOV 9° (P = 0.037). Age and the presence of drusen or subretinal drusenoid deposits were also tested without showing significant correlations.

Conclusions

Among the retinal layers examined, only the ONL thickness demonstrated a significant association with MPOV. Consequently, ONL thickness might serve as a potential biomarker related to MP levels.

Quantitative Autofluorescence at AMD's Beginnings Highlights Retinal Topography and Grading System Differences: ALSTAR2 Baseline

INTRODUCTION

The aims of the study were to describe baseline quantitative (short-wavelength) autofluorescence (qAF) findings in a large pseudophakic cohort at age-related macular degeneration (AMD)'s beginnings and to assess qAF8 as an outcome measure and evaluate Age-Related Eye Disease Study (AREDS) and Beckman grading systems.

METHODS

In the ALSTAR2 baseline cohort (NCT04112667), 346 pseudophakic eyes of 188 persons (74.0 ± 5.5 years) were classified as normal (N = 160 by AREDS, 158 by Beckman), early AMD (eAMD) (N = 104, 66), and intermediate AMD (iAMD) (N = 82, 122). Groups were compared via mean qAF intensities in a 6°-8° annulus (qAF8) and maps of differences between observations and the overall mean, divided by standard deviation (Z-score).

RESULTS

qAF8 did not differ significantly among diagnostic groups by either stratification (p = 0.0869 AREDS; p = 0.0569 by Beckman). Notably, 45 eyes considered eAMD by AREDS became iAMD by Beckman. For AREDS-stratified eyes, Z-score maps showed higher centrally located qAF for normal, near the mean in eAMD, and lower values for iAMD. Maps deviated from this pattern for Beckman-stratified eyes.

CONCLUSIONS

In a large sample of pseudophakic eyes, qAF8 does not differ overall from normal aging to iAMD but also does not capture the earliest AMD activity in the macula lutea. AREDS classification gives results more consistent with a slow decline in histologic autofluorescence than Beckman classification.

Age-Related Macular Degeneration, a Mathematically Tractable Disease

A progression sequence for age-related macular degeneration onset may be determinable with consensus neuroanatomical nomenclature augmented by drusen biology and eye-tracked clinical imaging. This narrative review proposes to supplement the Early Treatment of Diabetic Retinopathy Study (sETDRS) grid with a ring to capture high rod densities. Published photoreceptor and retinal pigment epithelium (RPE) densities in flat mounted aged-normal donor eyes were recomputed for sETDRS rings including near-periphery rich in rods and cumulatively for circular fovea-centered regions. Literature was reviewed for tissue-level studies of aging outer retina, population-level epidemiology studies regionally assessing risk, vision studies regionally assessing rod-mediated dark adaptation (RMDA), and impact of atrophy on photopic visual acuity. The 3 mm-diameter xanthophyll-rich macula lutea is rod-dominant and loses rods in aging whereas cone and RPE numbers are relatively stable. Across layers, the largest aging effects are accumulation of lipids prominent in drusen, loss of choriocapillary coverage of Bruch's membrane, and loss of rods. Epidemiology shows maximal risk for drusen-related progression in the central subfield with only one third of this risk level in the inner ring. RMDA studies report greatest slowing at the perimeter of this high-risk area. Vision declines precipitously when the cone-rich central subfield is invaded by geographic atrophy. Lifelong sustenance of foveal cone vision within the macula lutea leads to vulnerability in late adulthood that especially impacts rods at its perimeter. Adherence to an sETDRS grid and outer retinal cell populations within it will help dissect mechanisms, prioritize research, and assist in selecting patients for emerging treatments.

Choriocapillaris Impairment Is Associated With Delayed Rod-Mediated Dark Adaptation in Age-Related Macular Degeneration

Purpose

Progress toward treatment and prevention of age-related macular degeneration (AMD) requires imaging end points that relate to vision. We investigated choriocapillaris flow signal deficits (FD%) and visual function in eyes of individuals aged ≥60 years, with and without AMD.

Methods

One eye of each participant in the baseline visit of the Alabama Study on Early Age-Related Macular Degeneration 2 (ALSTAR2; NCT04112667) was studied. AMD presence and severity was determined using the Age-Related Eye Disease Study (AREDS) grading system. FD% was quantified using macular spectral domain optical coherence tomography angiography (OCTA) scans. Vision tests included rod-mediated dark adaptation (RMDA), best-corrected visual acuity, and contrast sensitivity (photopic and mesopic), and microperimetric light sensitivity (scotopic, mesopic, and photopic). Presence of subretinal drusenoid deposits (SDD) was determined using multimodal imaging.

Results

In 410 study eyes of 410 participants (mean [SD] age = 71.7 years [5.9]), FD% was higher in early AMD (mean [SD] = 54.0% [5.5], N = 122) and intermediate AMD (59.8% [7.4], N = 92), compared to normal (52.1% [5.3], N = 196) eyes. Among visual functions evaluated, RMDA showed the strongest association with FD% (r = 0.35, P < 0.0001), followed by contrast sensitivity (r = -0.22, P < 0.0001). Eyes with SDD had worse FD% (58.3% [7.4], N = 87), compared to eyes without SDD (53.4% [6.0], N = 323, P = < 0.0001).

Conclusions

Choriocapillaris FD% were associated with AMD severity and with impaired vision, especially RMDA. Reduced metabolic transport and exchange across the choriocapillaris-Bruch's membrane retinal pigment epithelium (RPE) complex, a causal factor for high-risk soft drusen formation, also may impair photoreceptor sustenance from the circulation. This includes retinoid resupply, essential to dynamic rod function.

Xanthophyll pigments dietary supplements administration and retinal health in the context of increasing life expectancy trend

Introduction

Medicine faces nowadays the trend of increasing life expectancy of human population, with the resulting increase of degenerative age related diseases prevalence, combined with the risks of less tempered sun radiations environment exposure. Under these circumstances, our work pointed out on evaluating the effect of some xanthophyll pigments dietary supplements, actually widely recommended, for prevention of retinal degenerative damages and for slowing down the progression of such age related changes if they have already occurred. These dietary supplements are already well known for their total antioxidant activity, proven by photochemiluminescence method using Total Antioxidant Capacity in Lipid soluble-substances procedure.

Materials and methods

The study recruited a number of 120 subjects equally divided on genders. The lot included a first group of 60 patients with comparable ages (all of them over 50 years and divided in 2 segments of age: 50-60 and over 60) and suffering from comparable retinal age-related degenerative abnormalities (mild/medium severity age-related macular degeneration according to Wisconsin Age-Related Maculopathy Grading System), and a second group, considered control, including a similar number of healthy, normal retina subjects belonging to same age and gender categories. There were evaluated at baseline the eye medical status and the retinal risk by specific methods: complete eye check-up, Amsler grid, specific standardized questionnaires focused on visual function and its impact on the quality of current life. Both groups, patients and control, received similar dosages of xanthophyll pigments dietary supplements including lutein and zeaxanthin during 18 months after baseline; at the end of this supplementation period a new evaluation was conducted. In the second part of the research all subjects involved received a new dietary supplement in which the same xanthophylls were enriched with C and E vitamins and oligo-elements Zinc and Copper. At the end of three years duration supplementation, the subjects were reevaluated and the paper presents the conclusions on the matter, pointing on the impact of xanthophyll supplements on visual health.

Results

Correlation tests were applied to the complete set of data. Correlation tests have values between -1 and +1. The value -1 represents the negative correlation (reverse proportionality) meanwhile the value +1 represents the positive correlation (direct proportionality). The charts show the curves that are fitting experimental data. The dependence is linear in nature, and the value R2, as it approaches more the value 1, represents a better match with the experimental data (the data are in a percentage of approximately 99% on these straight lines of type y = ax + b). In the charts, there were noted the average values of the scores for healthy control patients with "Control", and the average values of the scores for the patients with existing age related degenerative retinal pathology at baseline with "Patients".

Discussion

The retinal function and the impact of visual condition on health were both evaluated at baseline, 18 months and 36 months after baseline, by visual acuity, ophthalmoscopy fundus examination, Amsler test and by asking the subjects to answer the visual function questionnaires: EQ-5D, NEI-VFQ-25, as measures of health status quality and of the influence on welfare. The study revealed that under supplementation both control healthy subjects and patients with known degenerative retinal pathology included in the 50-60 years of age group evolved almost the same way, leading to the conclusion that administered xanthophyll pigments-based supplements, simple or enriched, managed to slow down the progression of abnormal degenerative vision loss to a rate comparable to physiological aging-related vision loss. It was also observed that intake of xanthophyll pigments dietary supplements preserved the general health condition and maintained relatively constant vision on the entire 36th months follow-up research duration in patients presented with existing age related degenerative retinal pathology at baseline. For healthy subjects, evaluation showed an improvement in results after dietary supplementation, with maintenance of constant vision and a significantly increase of general condition, in a positive sense. For subjects over the age of 60 dietary supplements intake was even more effective compared to younger group in providing better control of degenerative processes.

The Role of Oxidative Stress in the Aging Eye

Given the expanding elderly population in the United States and the world, it is important to understand the processes underlying both natural and pathological age-related changes in the eye. Both the anterior and posterior segment of the eye undergo changes in biological, chemical, and physical properties driven by oxidative stress. With advancing age, changes in the anterior segment include dermatochalasis, blepharoptosis, thickening of the sclera, loss of corneal endothelial cells, and stiffening of the lens. Changes in the posterior segment include lowered viscoelasticity of the vitreous body, photoreceptor cell loss, and drusen deposition at the macula and fovea. Age-related ocular pathologies including glaucoma, cataracts, and age-related macular degeneration are largely mediated by oxidative stress. The prevalence of these diseases is expected to increase in the coming years, highlighting the need to develop new therapies that address oxidative stress and slow the progression of age-related pathologies.