Biomedical subjects

B R Hammond

Publications and source records attributed to B R Hammond.

At least 19 recordsLinked to original sources

PubMed2001

Carotenoids in the retina and lens: possible acute and chronic effects on human visual performance.

(MP) that is composed of the hydroxy-carotenoids lutein and zeaxanthin. Although it appears that all humans have some quantity of these pigments within their retina, foveal concentrations tend to vary quite dramatically. This wide individual variability has prompted questions regarding possible functional consequences. At least two major nonexclusive hypotheses regarding the function of MP have been proposed. The "protection hypothesis" has received the most attention and is based on the possibility that MP could reduce the cumulative effects of damage due to light and oxygen and retard the development of age-related eye disease. The "acuity hypothesis" states that MP could improve visual resolution by absorbing short-wave light, which is easily scattered and poorly focused. In this article, we review evidence that lutein and zeaxanthin could improve human visual performance through both acute optical effects at the site of the retina and by maintaining health and functional integrity of the retina and crystalline lens.

Aging↗

PubMed2001

Macular pigment optical density in a midwestern sample.

OBJECTIVE: To assess the distribution of the macular pigments (MPs) lutein (L) and zeaxanthin (Z) in a healthy sample more representative of the general population than past studies and to determine which dietary factors and personal characteristics might explain the large interindividual differences in the density of these MPs. DESIGN: Prevalence study in a self-selected population. PARTICIPANTS: Two hundred eighty healthy adult volunteers, consisting of 138 men and 142 women, between the ages of 18 and 50 years, recruited from the general population. METHODS: MP optical density was measured psychophysically at 460 nm by use of a 1 degrees test field. Serum was analyzed for carotenoid and vitamin E content with reversed-phase high-performance liquid chromatography. Usual intakes of nutrients over the past year were determined by means of a food frequency questionnaire. MAIN OUTCOME MEASURES: MP optical density. RESULTS: Mean MP optical density measured 0.211 +/- 0.13, which is approximately 40% lower than the average reported in smaller, less representative studies. MP density was 44% lower in the bottom versus the top quintile of serum L and Z concentrations. Similarly, MP density was 33% lower in the bottom compared with the top quintile of L and Z intake. MP density was 19% lower in blue-grey-eyed subjects than in subjects with brown-black irises. When all variables were considered together in a general linear model of determinants of MP, statistically significant (P < 0.05) relationships were found between MP density and serum L and Z, dietary L and Z intake, fiber intake, and iris color. CONCLUSIONS: These data suggest that MP values in this healthy adult population are lower than in smaller select samples. Moreover, these data indicate that MP is related to serum L and Z, dietary L and Z intake, fiber intake, and iris color.

Adolescent↗

PubMed2001

Relation between dietary intake, serum concentrations, and retinal concentrations of lutein and zeaxanthin in adults in a Midwest population.

BACKGROUND: Information on concentrations of retinal carotenoids (macular pigment, or MP) is of particular interest because MP protects against age-related macular degeneration, the leading cause of irreversible blindness in the United States. OBJECTIVE: This study was designed to evaluate the relation between dietary intake, blood concentrations, and retinal concentrations of carotenoids in a large group of volunteers. DESIGN: Two hundred eighty volunteers in the Indianapolis area completed health and diet questionnaires, donated a blood sample, and participated in MP density assessment to determine retinal carotenoid status. Dietary intake was assessed by food-frequency questionnaire. Serum concentrations of lutein, zeaxanthin, and beta-carotene were measured by HPLC. MP optical density (MPOD) was determined psychophysically with a 460-nm, 1 degrees test stimulus. RESULTS: Average MPOD was 0.21 +/- 0.13. Average intakes of lutein + zeaxanthin and beta-carotene were 1101 +/- 838 and 2935 +/- 2698 microg/d, respectively. Although several key dietary intake variables (eg, lutein + zeaxanthin and beta-carotene) differed by sex, no significant sex differences were found in either serum concentrations of lutein and zeaxanthin or MPOD. Serum beta-carotene concentrations were significantly higher in women than in men. Serum lutein + zeaxanthin and dietary intake of lutein + zeaxanthin were significantly correlated and significantly related to variations in MPOD (r = 0.21, P < 0.001, and r = 0.25, P < 0.001, respectively). CONCLUSIONS: Retinal carotenoids can be measured in epidemiologic studies. In this study, MPOD was associated with lutein + zeaxanthin in the diet and the serum. Retinal concentrations, however, were influenced by other factors as well. To understand the effect of dietary lutein + zeaxanthin intake on the retina and risk of age-related eye disease, future studies should include measures of macular concentrations of these pigments.

Adult↗

PubMed2001

Macular pigment density measured by autofluorescence spectrometry: comparison with reflectometry and heterochromatic flicker photometry.

We present a technique for estimating the density of the human macular pigment noninvasively that takes advantage of the autofluorescence of lipofuscin, which is normally present in the human retinal pigment epithelium. By measuring the intensity of fluorescence at 710 nm, where macular pigment has essentially zero absorption, and stimulating the fluorescence with two wavelengths, one well absorbed by macular pigment and the other minimally absorbed by macular pigment, we can make accurate single-pass measurements of the macular pigment density. We used the technique to measure macular pigment density in a group of 159 subjects with normal retinal status ranging in age between 15 and 80 years. Average macular pigment density was 0.48 +/- 0.16 density unit (D.U.) for a 2 degrees -diameter test field. We show that these estimates are highly correlated with reflectometric (mean: 0.23 +/- 0.07 D.U.) and psychophysical (mean: 0.37 +/- 0.26 D.U.; obtained by heterochromatic flicker photometry) estimates of macular pigment in the same subjects, despite the fact that systematic differences in the estimated density exist between techniques. Repeat measurements over both short- and long-time intervals indicate that the autofluorescence technique is reproducible: The mean absolute difference between estimates was less than 0.05 D.U., superior to the reproducibility obtained by reflectometry and flicker photometry. To understand the systematic differences between density estimates obtained from the different methods, we analyzed the underlying assumptions of each technique. Specifically, we looked at the effect of self-screening by visual pigment, the effect of changes in optical property of the deeper retinal layers, including the role of retinal pigmented epithelium melanin, and the role of secondary fluorophores and reflectors in the anterior layers of the retina.

Adult↗

PubMed2001

Macular pigment optical density before and after cataract extraction.

PURPOSE: Psychophysical methods of measuring macular pigment (MP) use comparisons of short- and midwave light in the fovea and parafovea to derive optical density estimates. This light must pass through the crystalline lens before absorption by the MPs can occur. The effect of lens absorption on these measures has not been adequately determined. The present study assesses the influence of lens absorption on MP measurements by comparing MP optical density (MPOD) measured before and after cataract extraction. METHODS: MPOD was measured using flicker photometry in free view at 458 nm with a 1 degrees stimulus. Twenty-nine eyes from 24 patients with cataracts sufficiently severe to require cataract extraction were evaluated. RESULTS: In the entire group of 24 patients, the mean (+/-SD) age measured 68.7 +/- 9.5 years, and the mean MPOD measured 0.19 +/- 0.11. For all 29 eyes measured, MPOD averaged 0.206 +/- 0.13 before and 0.18 +/- 0.12 after cataract extraction. MPOD measurements at the two time points (mean 8.1 +/- 4.7 weeks after surgery) were highly correlated (r = +0.58), suggesting that a cataractous lens does not influence the MP measurement technique. CONCLUSIONS: Psychophysical techniques can be used to obtain reliable measurements of MP in elderly subjects, even in those with cataracts. Moreover, differences in retinal illuminance due to varying opaqueness of the crystalline lens do not seem to have a measurable influence on MPOD.

Aged↗

PubMed2000

Relation among serum and tissue concentrations of lutein and zeaxanthin and macular pigment density.

BACKGROUND: Lutein and zeaxanthin are the only carotenoids in the macular region of the retina (referred to as macular pigment [MP]). Foods that are rich in lutein and zeaxanthin can increase MP density. Response to dietary lutein and zeaxanthin in other tissues has not been studied. OBJECTIVE: The objective of this study was to examine tissue responses to dietary lutein and zeaxanthin and relations among tissues in lutein and zeaxanthin concentrations. DESIGN: Seven subjects consumed spinach and corn, which contain lutein and zeaxanthin, with their daily diets for 15 wk. At 0, 4, 8, and 15 wk and 2 mo after the study, serum, buccal mucosa cells, and adipose tissue were analyzed for carotenoids, and MP density was measured. RESULTS: Serum and buccal cell concentrations of lutein increased significantly from baseline during dietary modification. Serum zeaxanthin concentrations were greater than at baseline only at 4 wk, whereas buccal cell and adipose tissue concentrations of zeaxanthin did not change. Adipose tissue lutein concentrations peaked at 8 wk. Changes in adipose tissue lutein concentration were inversely related to the changes in MP density, suggesting an interaction between adipose tissue and retina in lutein metabolism. To investigate the possibility of tissue interactions, we examined cross-sectional relations among serum, tissue, and dietary lutein concentrations, anthropometric measures, and MP density in healthy adults. Significant negative correlations were found between adipose tissue lutein concentrations and MP for women, but a significant positive relation was found for men. CONCLUSION: Sex differences in lutein metabolism may be an important factor in tissue interactions and in determining MP density.

Adipose Tissue↗

PubMed2000

Olestra consumption is not associated with macular pigment optical density in a cross-sectional volunteer sample in Indianapolis.

The associations between the intake of the fat-substitute olestra and the concentrations of macular carotenoid pigments and serum lutein and zeaxanthin were investigated in a volunteer cross-sectional sample in Indianapolis. The study was conducted in January through March, 1998 after olestra-containing savory snacks had been sold in central Indiana for a year. Volunteers (n = 280) aged 18-50 y were recruited to make a single clinic visit during which macular pigment optical density (MPOD) was determined by psychophysical flicker photometry, serum was obtained for determination of lutein and zeaxanthin concentration, usual intake of olestra, carotenoids and nutrients were assessed by 1-y food frequency questionnaire, and health habits including smoking, physical characteristics such as eye color, demographics and medical history were determined by questionnaire. Intake of olestra at least one time per month for the past year was reported by 81:280 subjects and their mean, median and 90(th) percentile intakes were 1.09, 0.34 and 2.43 g olestra/d, respectively. Mean macular pigment optical density was not significantly different between olestra consumers and nonconsumers (0.213 +/- 0.014 vs. 0.211 +/- 0.010) nor was serum lutein and zeaxanthin concentration (0.361 +/- 0.017 vs. 0.375 +/- 0. 013 micromol/L) or intake (1242 +/- 103 mg/d vs. 1042 +/- 58 mg/d) in one-way or two-way ANOVA. Olestra intake was not associated with MPOD or serum lutein and zeaxanthin before or after correction for significant covariates of MPOD. Thus, olestra intake over the past year in a cross-sectional volunteer sample in Indianapolis was not associated with MPOD.

Adult↗

PubMed2000

Macular pigment optical density in a Southwestern sample.

PURPOSE: Increasing evidence implicates macular pigment in protecting the retina and retinal pigment epithelium from light-initiated oxidative damage. Little information, however, is available regarding "average" levels of macular pigment in the general population. This study was designed to assess macular pigment in a high-light environment and to determine what personal characteristics influence macular pigment density in that sample. METHODS: Macular pigment optical density was measured psychophysically using a 1 degree, 460-nm test stimulus. Personal data were collected using a questionnaire. RESULTS: 217 subjects (79 men, 138 women) were recruited from the Phoenix metropolitan area (age range = 17-92 years). The average macular pigment density was 0.22 +/- 0.13. There was a slight tendency for macular pigment density in this sample to decline with age (r = -0.14, P < 0.02). Average macular pigment density was significantly lower in women versus men (P < 0.05), lower in individuals with light-colored irises versus dark-colored irises (P < 0.009), and lower in heavy smokers compared to light (P < 0.0045) and never (P < 0.034) smokers. CONCLUSIONS: Macular pigment density was lower than average levels obtained from the Northeast but similar to average values obtained in a recent study of adults recruited from Indianapolis. Consistent with past studies, MP density was 13% lower in women and 18% lower in individuals with light- versus dark-colored irises. The relation of smoking to macular pigment density was only significant for those current smokers who smoked more than 10 cigarettes per day (about a 25% reduction). The large number of individuals in this sample with low macular pigment density motivates the need for population-based assessment of the possibly poor nutritional state of the average American's retina.

Adolescent↗

PubMed2000

Iris color and age-related changes in lens optical density.

PURPOSE: Epidemiologic evidence indicates that dark iris color increases risk of age-related cataract. No information is currently available, however, on the effects of iris color on the lens prior to cataract development. In this study, we relate iris color to lens optical density (OD) in individuals without frank cataract. METHODS: 90 subjects with blue or green irises (light color) were compared with 87 subjects having hazel, brown, or black irises (dark color). Lens OD was measured psychophysically by comparing scotopic thresholds obtained at 410 (measuring) and 550 nm (reference). Stimuli were presented in Maxwellian view. RESULTS: The groups with light and with dark iris color did not differ significantly in smoking habits, dietary patterns, or age. Despite other similarities between the groups, lens OD was significantly (p < 0.024) higher in the group with dark irises. The higher OD of the dark iris group was due to differences in the older subjects (> 45 years, p < 0.005), rather than the younger subjects (20-45 years) who showed no differences in lens OD. CONCLUSION: Our data indicate that iris pigmentation may be directly related to age-associated increases in lens OD.

Adult↗

PubMed1999

Smoking and lens optical density.

Epidemiological evidence indicates that smoking increases the risk of age-related cataract. No information is currently available, however, on the effects of smoking on the lens prior to cataract development. In this study, we relate smoking behavior to lens optical density (OD) in younger individuals without frank cataract. Fifty three never smokers and 41 current smokers were compared directly. Thirty one past smokers were tested to examine the relationship between years since smoking cessation and lens OD. Lens OD was measured psychophysically by comparing scotopic thresholds obtained at 410 (measuring) and 550 nm (reference). Stimuli were presented in Maxwellian view. The smokers in the sample smoked an average of 17.3 +/- 11.3 cigarettes/day for 20.4 +/- 12 years. No significant differences (other than in fat intake) were found between the smokers and nonsmokers in iris color, dietary patterns, or age. Despite their overall similarity, lens OD was significantly (p = 0.005) higher in the smokers. Moreover, we found a significant dose-response relationship (p = 0.02) between smoking frequency and lens OD. There was also a weak relationship between smoking frequency and lens OD for past smokers (p = 0.06), but no relationship between lens OD and years since smoking cessation. Our data indicate that smoking is directly related to age-related increases in lens OD throughout life and that these increases persist even after smoking cessation.

Adult↗

PubMed1999

A practical method for measuring macular pigment optical density.

PURPOSE: Increasing evidence indicates that the macular pigments (MP) protect the central retina and may retard macular disease. For that reason, a practical method for measuring MP that does not require elaborate optics and can be applied to diverse populations by operators with a modest amount of experience was developed and validated. METHODS: A small tabletop device based on light-emitting diodes (LEDs) as the light source with electronic controls was constructed. Macular pigment was measured with the tabletop device with a 1 degrees test stimulus at 460 nm using heterochromatic flicker photometry, and the results were compared with measurements using a traditional three-channel Maxwellian view system with a xenon-arc source. RESULTS: Macular pigment density of 30 subjects (age range, 16-60 years) was measured with both stimulus systems. Macular pigment measured with the LED tabletop device in free view was highly correlated with MP measured in Maxwellian view (y = -0.03 + 1.06x, r = +0.95). The average absolute difference between the two techniques was 0.04 (SD, 0.03). The new technique was not significantly affected by variations in lens optical density, pupil size, or small head movements. CONCLUSIONS: Psychophysical measurement of MP provides a unique opportunity to make repeated noninvasive assessment of the concentration of a protective nutrient in the retina. The availability of this new device should make this measurement technology accessible to a wide variety of investigators for application to diverse populations.

Adolescent↗

PubMed1998

Scotopic sensitivity: relation to age, dietary patterns, and smoking status.

PURPOSE: Although previous data suggest that rod-mediated sensitivity decreases with age, this decrease may be insignificant when only healthy individuals younger than 65 years are considered. In this study, we assess the relationship between age and scotopic sensitivity loss in subjects younger than 65 years to determine whether scotopic sensitivity losses can be detected when confounding factors are considered (including iris color, smoking status, and dietary patterns) and a large sample size is used. METHODS: A total of 121 subjects (aged 20 to 63 years) were tested under dark-adapted (scotopic) conditions. Scotopic sensitivity was measured as absolute thresholds to a 2.8 degree, 550-nm test presented at 6 degrees in the temporal hemiretina. Stimuli were presented in Maxwellian view. RESULTS: When all the subjects were considered together, there was a slight nonsignificant trend for scotopic sensitivity to decline with age (p < 0.11). This tendency was largely driven by the older (45 to 63 years) past and never smokers and was statistically significant (p < 0.024 and p < 0.05, respectively) when those two groups were analyzed separately. Scotopic sensitivity for the younger (20 to 44 years) past, current, and never smokers did not decline with age. When all the variables were considered in a general model, dietary intake of vitamin E explained a significant amount of the variation in scotopic sensitivity (p < 0.03). No relationships were found between scotopic sensitivity and iris color. CONCLUSIONS: Age-related losses in scotopic sensitivity before age 65 are slow. Moreover, individual variations in scotopic sensitivity for younger subjects is minimal, even in the presence of dramatic stressors such as long-term, heavy exposure to cigarette smoke. These data suggest that measurements of scotopic sensitivity may not be good indicators of the retinal health of individuals younger than 65 years.

Adult↗

PubMed1998

Preservation of visual sensitivity of older subjects: association with macular pigment density.

PURPOSE: The authors investigated how individual differences in macular pigment (MP) density are related to loss of visual sensitivity with age. METHODS: Macular pigment and visual sensitivity of 27 healthy older subjects (aged 60-84 years) were compared with data from 10 younger subjects (aged 24-36 years). Macular pigment density was measured psychophysically with a centrally fixated stimulus 1 degree in diameter. Photopic increment sensitivity in the fovea was measured as thresholds for centrally fixated 1 degree stimuli on a bright yellow background. Foveal sensitivity of the pi-1 mechanism driven by the S cones was measured with 440-nm light. Photopic increment thresholds not determined by the pi-1 mechanism were measured with 550-nm light. Sensitivity was specified at the photoreceptor outer segments by individually correcting for psychophysically determined lens density and MP density. Dark-adapted (scotopic) sensitivity of rod-dominated visual mechanisms was measured in the parafovea with 550-nm light at 8 degrees eccentricity. RESULTS: Consistent with past reports, photopic sensitivity declined significantly with age for both 440-nm (P < 0.025) and 550-nm (P < 0.0003) light. For older subjects, photopic sensitivity was positively related to MP density, although more strongly for 440-nm (P < 0.001) than for 550-nm (P < 0.01) light. Parafoveal scotopic sensitivity of the older subjects was also positively related to MP density (P < 0.02). Visual sensitivity of the young subjects was not significantly related to MP density. CONCLUSIONS: For subjects older than 60 years, visual sensitivity of those with high MP density was not significantly different from that of young subjects. Conversely, older subjects with low MP density had lower sensitivity than young subjects. Although this study cannot prove causality, the results show that high MP density was associated with the retention of youthful visual sensitivity, which suggested that MP may retard age-related declines in visual function.

Adaptation, Ocular↗

PubMed1997

Density of the human crystalline lens is related to the macular pigment carotenoids, lutein and zeaxanthin.

PURPOSE: Although oxidative stress may play an important role in the development of age-related cataract, the degree of protection reported for antioxidant vitamins and carotenoids has been inconsistent across studies. These varied results may be due in part to the lack of good biomarkers for measuring the long-term nutritional status of the eye. The present experiments investigated the relationship between retinal carotenoids (i.e., macular pigment), used as a long-term measure of tissue carotenoids, and lens optical density, used as an indicator of lens health. METHODS: Macular pigment (460 nm) and lens (440, 500, and 550 nm) optical density were measured psychophysically in the same individuals. Groups of younger subjects--7 females (ages 24 to 36 years), and 5 males (ages 24 to 31 years)--were compared with older subjects--23 older females (ages 55 to 78 years), and 16 older males (ages 48 to 82 years). RESULTS: Lens density (440 nm) increased as a function of age (r = 0.65, p < 0.001), as expected. For the oldest group, a significant inverse relationship (y = 1.53-0.83x, r = -0.47, p < 0.001) was found between macular pigment density (440 nm) and lens density (440 nm). No relationship was found for the youngest group (p < 0.42). CONCLUSIONS: The main finding of this study was an age-dependent, inverse relationship between macular pigment density and lens density. Macular pigment is composed of lutein and zeaxanthin, the only two carotenoids that have been identified in the human lens. Thus, an inverse relationship between these two variables suggests that lutein and zeaxanthin, or other dietary factors with which they are correlated, may retard age-related increases in lens density.

Adult↗

PubMed1997

Individual variations in the spatial profile of human macular pigment.

Individual variations in the spatial profile of macular pigment (MP) density were measured for 32 subjects. Peak density of MP measured with a 460-nm, 12-arcmin stimulus averaged 0.58, standard deviation (SD) = 0.26, with a range of 0.175 to 1.39. To assess the symmetry of the MP distribution, MP density was measured on the horizontal and vertical meridians at +/-1 deg eccentricity. The density varied by no more than 16% at these four locations, indicating a basically symmetric distribution. Based on a linear interpolation between measured locations, the width of the spatial distribution of MP at half the maximal density averaged 1.03 deg, SD = 0.38, with a range of 0.25 to 1.9 deg. The average spatial profile of MP density across subjects was fitted with both an exponential and a Gaussian function. An exponential decay with eccentricity explained more variance in the data than did a Gaussian function. Assuming an exponential decay with eccentricity, once MP density has been measured in the center of the retina (denoted A), MP density at more eccentric locations (X, deg) can be predicted with a standardized equation (MP = A x 10(-0.42x)). For individual cases, small deviations from an exponential function suggest the existence of minor flanking peaks or shoulders for 40% of the subjects. We also examined the temporal stability of the MP profile of four subjects over a time span of 4-14 months and for a single spatial location for ten subjects over a time span of 1-16 years. These longitudinal data show that differences in MP density among subjects are maintained over time, if dietary patterns are stable.

Adult↗

PubMed1997

Dietary modification of human macular pigment density.

PURPOSE: The retinal carotenoids lutein (L) and zeaxanthin (Z) that form the macular pigment (MP) may help to prevent neovascular age-related macular degeneration. The purpose of this study was to determine whether MP density in the retina could be raised by increasing dietary intake of L and Z from foods. METHODS: Macular pigment was measured psychophysically for 13 subjects. Serum concentrations of L, Z, and beta-carotene were measured by high-performance liquid chromatography. Eleven subjects modified their usual daily diets by adding 60 g of spinach (10.8 mg L, 0.3 mg Z, 5 mg beta-carotene) and ten also added 150 g of corn (0.3 mg Z, 0.4 mg L); two other subjects were given only corn. Dietary modification lasted up to 15 weeks. RESULTS: For the subjects fed spinach or spinach and corn, three types of responses to dietary modification were identified: Eight "retinal responders" had increases in serum L (mean, 33%; SD, 22%) and in MP density (mean, 19%; SD, 11%); two "retinal nonresponders" showed substantial increases in serum L (mean, 31%) but not in MP density (mean, -11%); one "serum and retinal nonresponder" showed no changes in serum L, Z, or beta-carotene and no change in MP density. For the two subjects given only corn, serum L changed little (+11%, -6%), but in one subject serum Z increased (70%) and MP density increased (25%). CONCLUSIONS: Increases in MP density were obtained within 4 weeks of dietary modification for most, but not all, subjects. When MP density increased with dietary modification, it remained elevated for at least several months after resuming an unmodified diet. Augmentation of MP for both experimental and clinical investigation appears to be feasible for many persons.

Adult↗

PubMed1996

Iris color and macular pigment optical density.

The present study was designed to assess the relationship between iris color and macular pigment optical density. Both melanin and carotenoids (responsible for iris color and macular pigment composition, respectively) appear to protect the retina through similar mechanisms and higher concentrations may reduce the incidence of retinal degenerations. To evaluate this relationship, 95 subjects were examined and the following variables were measured: iris color; macular pigment optical density (MP); plasma concentrations of lutein and zeaxanthin and beta-carotene; dietary intake of lutein and zeaxanthin and beta-carotene; and total fat intake. Iris color was determined by self assessment and classified as blue or gray (group I), green or hazel (group II) or brown or black (group III). MP density was measured psychophysically by measuring foveal and parafoveal sensitivities to lights of 460 and 550 nm, using the method of heterochromatic flicker photometry. Plasma carotenoid concentrations were measured using reverse-phase high-performance liquid chromatography. Dietary intake was determined by a detailed food-frequency questionnaire. Despite similarities in diet and in blood concentrations of carotenoids, significant differences in macular pigment density (P < 0.02) were found for different colored irises (group I, n = 38, MP = 0.25; group II, n = 26, MP = 0.32; group III, n = 31, MP = 0.38). The covariation of iris color and MP indicates that past epidemiologic studies have not adequately determined the independent effects of either factor. The relationship of MP and iris color may be the result of one or two factors: the evolution of a shared tendency to accumulate melanin and carotenoids due to similar environmental pressures (e.g. light and oxygen); and/or MP might be depleted due to the tendency for eyes with light irises to transmit more light than eyes with dark irises, thus causing increased oxidative stress.

Adult↗

PubMed1996

Sex differences in macular pigment optical density: relation to plasma carotenoid concentrations and dietary patterns.

Sex differences in macular pigment (MP) optical density (measured psychophysically) were examined. Concentrations of lutein and zeaxanthin (L and Z) (non-separated) and beta-carotene (BC) in the blood were determined using reverse phase high-performance liquid chromatography. Dietary intake of L and Z, BC, fat, and iron were estimated by questionnaire. Males had 38% higher MP density than females (P < 0.001) despite similar plasma carotenoid concentrations and similar dietary intake (except for fat). Dietary intake of carotenoids, fat and iron, as well as plasma concentrations of L and Z were positively related to MP density in males. Conversely, only plasma L and Z was related to MP density for females, and dietary fat was negatively related to MP density. Sex differences in protection of the retina by MP and in the relationship between the retina, blood and diet could be a factor in the incidence of retinal diseases, especially age-related macular degeneration.

Adult↗