In the lateral geniculate nucleus (LGN) the large neurons of the magnocellular layers are functio... more In the lateral geniculate nucleus (LGN) the large neurons of the magnocellular layers are functionally distinct and anatomically segregated from the small neurons of the parvocellular layers. This segregation of large and small cells is not maintained in the primary visual cortex (V1); instead a heterogeneous mixture of cells occurs, particularly in the output layers. Nevertheless, our results indicate that for the middle and upper layers of V1, cell size remains a predictor of physiological properties. We recorded extracellularly from neurons in V1 of alert monkeys and analyzed the amplitude, duration, and polarity of the action potentials of 199 cells. Of 156 cells that could be assigned to specific cortical layers, 137 (88%) were localized to the middle and upper cortical layers, layer 4 and above. We summarize evidence that the large-amplitude spikes are discharged by large cells, whereas small-amplitude spikes are the action potentials of smaller cells. Large spikes were predominantly negative and of longer duration, whereas small spikes were predominantly positive and briefer. The putative large cells had lower ongoing activity, smaller receptive field activating regions and higher selectivity for stimulus geometry and stimulus motion than the small cells. The contrasting properties of the large and the small cells were illustrated dramatically in simultaneous recordings made from adjacent cells. Our results imply that there may be an anatomic pairing or clustering of small and large cells that could be integral to the functional organization of the cortex. We suggest that the small and the large cells of area V1 have different roles, such that the small cells may shape the properties of the large output cells. If some of the small cells are also output cells, then cell size should be a predictor of the type of information being sent to other brain regions. Because of their high activity and relative ease of stimulation, the small cells also may contribute disproportionately to in vivo images based on metabolic responses such as changes in blood flow.
In the creation of a digital version of this manuscript, D. Max Snodderly's name was erroneously ... more In the creation of a digital version of this manuscript, D. Max Snodderly's name was erroneously reproduced as D. Ma Snodderly. The publisher would like to apologize for the error.
When we view a scene, saccades separate brief periods of fixation during which the information is... more When we view a scene, saccades separate brief periods of fixation during which the information is acquired and processed. Mounting evidence indicates that the retinal motion introduced by fixational drift enhances fine detail, but physiological studies have not analyzed its effect. Responses of visual neurons to natural images are generally studied as if the eye is stationary during fixation. One reason for this situation is the challenge of measuring ocular drift with high accuracy and precision. Here we assess precision and resolution of two eyetracking systems, an eye coil (Remmel labs EM6) and a dual-Purkinje image eyetracker, (DPI v.6), to support neural and psychophysical studies of natural images with high precision during drift periods. We examined these systems noise with a model eye and eye coil mimicking the signal from a real eye. The impact of system noise on the measurements was characterized. The optimized eye coil system with a bandpass of 0-320 Hz had an RMS noise level of 0.18'~0.27', and the slow drift over a period of 7 min was 0.52' ± 0.16' (N=10). The RMS noise level of a DPI eyetracker was of 0.35' for both the horizontal and the vertical axes, and the slow drift over a period of 10 min was 0.7' ± 0.20' (N=6). By comparing the power spectrum of the system noise with ocular drift recorded from human subjects and a monkey, we determined the optimal filter to characterize drift speed. We also identified a high frequency tremor that varied between 50 and 100 Hz. Our results across the humans and the monkey consistently showed that ocular speed during fixation is much faster than previously thought, and tremor is sometimes larger than expected. These results can facilitate the development of standard procedures for optimizing study of the dynamics of microscopic ocular motion. Meeting abstract presented at VSS 2015.
To examine the association between intermediate age-related macular degeneration (AMD) and the op... more To examine the association between intermediate age-related macular degeneration (AMD) and the optical density of macular pigment (MPOD), which is composed of lutein and zeaxanthin from the diet. Design: Cross-sectional cohort study. Participants: We included 1698 of 2005 women ages 54 to 86 years and participating in the Carotenoids in Age-Related Eye Disease Study, an ancillary study of the Women's Health Initiative. Methods: The MPOD was measured noninvasively by heterochromatic flicker photometry. Fundus photographs were taken to document prevalent AMD. Main Outcome Measures: Intermediate AMD (n ϭ 305) and two subtypes-large drusen (n ϭ 233) and pigmentary abnormalities (n ϭ 157). Results: After adjusting for covariates, the odds ratio (OR) and 95% confidence interval (CI) for AMD among women in quintile (Q) 5 (n ϭ 339) versus 1 (n ϭ 340) for MPOD was 1.4 (0.9, 2.1). However, after excluding women with possible unstable diets and recent supplement use due to chronic disease history, associations reversed (OR Q2-5 vs. 1, 0.8; 95% CI, 0.5-1.2), but remained nonsignificant. Associations also differed between middle-aged (54-69 years) and older (Ն70 years) women (P-interaction ϭ 0.09), but less so, after excluding women who were likely to have unstable diets: adjusted ORs (95% CI) were 0.5 (0.3-1.0; P ϭ 0.08) for intermediate AMD among middle-aged women (n ϭ 516) with MPOD in Q2 to Q5 versus 1 and 1.0 (0.5-2.0; P ϭ 0.90) for older women (n ϭ 422). Conclusions: The MPOD is not cross-sectionally associated with AMD. The inconsistency of relationships across age groups and in subgroups of women who are likely to have more stable diets suggests that cross-sectional associations may be biased and highlights the need to study these relationships prospectively. Ophthalmology 2008;
Investigative Ophthalmology & Visual Science, Mar 28, 2013
PURPOSE. To investigate genetic determinants of macular pigment optical density in women from the... more PURPOSE. To investigate genetic determinants of macular pigment optical density in women from the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study of the Women's Health Initiative Observational Study. METHODS. 1585 of 2005 CAREDS participants had macular pigment optical density (MPOD) measured noninvasively using customized heterochromatic flicker photometry and blood samples genotyped for 440 single nucleotide polymorphisms (SNPs) in 26 candidate genes related to absorption, transport, binding, and cleavage of carotenoids directly, or via lipid transport. SNPs were individually tested for associations with MPOD using least-squares linear regression. RESULTS. Twenty-one SNPs from 11 genes were associated with MPOD (P 0.05) after adjusting for dietary intake of lutein and zeaxanthin. This includes variants in or near genes related to zeaxanthin binding in the macula (GSTP1), carotenoid cleavage (BCMO1), cholesterol transport or uptake (SCARB1, ABCA1, ABCG5, and LIPC), long-chain omega-3 fatty acid status (ELOVL2, FADS1, and FADS2), and various maculopathies (ALDH3A2 and RPE65). The strongest association was for rs11645428 near BCMO1 (b A ¼ 0.029, P ¼ 2.2 3 10 À4). Conditional modeling within genes and further adjustment for other predictors of MPOD, including waist circumference, diabetes, and dietary intake of fiber, resulted in 13 SNPs from 10 genes maintaining independent association with MPOD. Variation in these single gene polymorphisms accounted for 5% of the variability in MPOD (P ¼ 3.5 3 10 À11). CONCLUSIONS. Our results support that MPOD is a multi-factorial phenotype associated with variation in genes related to carotenoid transport, uptake, and metabolism, independent of known dietary and health influences on MPOD.
Eye position of two macaques and two humans was recorded while they detected the unpredictable di... more Eye position of two macaques and two humans was recorded while they detected the unpredictable dimming of a hxation spot in a dark or a light environment. Fixational saccades often had complex waveforms that resulted from clustering of two or more saccadic displacements with no intervening drift periods. In the dark, all subjects had low frequencies of saccade clusters (0.15-0.61/set). Three of the subjects increased the frequency of saccade clusters and decreased the magnitude of the displacements when the task was performed in the normally lighted laboratory. The higher saccade frequencies in the light did not automatically result in greater dispersion of eye position. One of the humans, who had the lowest saccade frequency, was relatively unaffected by the stimulus conditions. The change in stimulus conditions had a more pronounced effect on the fixational eye movements of the macaques than the humans. In the dark, the macaques made saccades mostly down and nasal, but in the light the saccadic displacements occurred over a wider range of angular directions. Mean eye position was higher in the dark than in the light. The humans altered the direction of their saccadic displacements very little and did not change their mean eye position when they switched from a dark to a lighted environment. The influence of a lighted environment is interpreted as an interaction between foveolar and peripheral retinal inputs. The results suggest that tlxational saccades may have mom than one role, perhaps including stimulation of pathways originating in the peripheral retina. These peripheral field inputs have a stronger effect on the fixational control system of macaques than of humans. Eye movements Fixation Saccades Primates
Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye ... more Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye movements. While these movements are often disregarded as noise, the temporal modulations they introduce to retinal receptors are significant. However, analysis of these input modulations is challenging because the intersaccadic eye motion is close to the resolution limits of most eyetrackers, including widespread pupil-based video systems. Here, we analyzed in depth the limits of two high-precision eyetrackers, the Dual-Purkinje Image and the scleral search coil, and compared the intersaccadic eye movements of humans to those of a non-human primate. By means of a model eye we determined that the resolution of both techniques is sufficient to reliably measure intersaccadic ocular activity up to approximately 80 Hz. Our results show that the characteristics of ocular drift are remarkably similar in the two species and that a clear deviation from a scale-invariant spectrum occurs in the range between 50-100 Hz, generally attributed to ocular tremor. The amplitude of this deviation differs on the two axes of motion. In addition to our experimental observations, we suggest basic guidelines to evaluate the performance of eyetrackers and to optimize experimental conditions for the measurement of ocular drift and tremor.
The American Journal of Clinical Nutrition, Jun 1, 2000
Background: Lutein and zeaxanthin are the only carotenoids in the macular region of the retina (r... more 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.
In many ocular diseases the retinal thickness is altered due to edema or atrophy. We have develop... more In many ocular diseases the retinal thickness is altered due to edema or atrophy. We have developed a method to measure the retinal thickness and thus provide earlier diagnosis and improve therapy monitoring. The application in humans has provided encouraging results. (1,2) To establish the method further, comparison between in vivo and in vitro thickness measurements in the same eye are desirable. The layers from which light is reflected and detected by the in vivo method can be identified and more information about the presence of tissue distortions arising from the in vitro method during preparation can be acquired. We present the comparison between locally measured thickness values in a cynomolgus monkey and measurements made by light microscopy of the whole mounted retina.
PURPOSE. To compare action spectra for visual discomfort in the fovea and the parafovea and to de... more PURPOSE. To compare action spectra for visual discomfort in the fovea and the parafovea and to determine the effect of macular pigment (MP). METHODS. Visual discomfort thresholds to lights from 440 to 600 nm were obtained for six young (<35 y), visually normal subjects with a wide range of MP densities (0.10-0.71 at 30 0 eccentricity). Foveal and parafoveal conditions were assessed. Discomfort thresholds were also obtained for xenon-white light (partially absorbed by MP), and a broadband yellow (outside the absorption band of MP). MP was measured psychophysically using heterochromatic flicker photometry (HFP). RESULTS. For the parafovea, discomfort sensitivity (1/threshold) increased sharply with decreasing wavelength for all subjects. Commensurate with a subject's MP level, MP significantly reduced visual discomfort to short wavelengths (including xenon-white light) for central viewing. CONCLUSIONS. MP simultaneously reduces visual discomfort and protects from light damage at short wavelengths. As a result, MP increases the range of safe and comfortable light levels. Because higher light levels enable improved visual sensitivity for fine detail, these findings indicate that the spectral absorption properties and spatial distribution of MP combine to protect the retina while enhancing visual performance. The action spectrum for visual discomfort closely matches the risk for acute light damage to the retinal pigment epithelium, and it is consistent with a major influence from the intrinsically photosensitive retinal ganglion cells containing melanopsin. We suggest that MP interacts with nonimage-forming retinal input to achieve the dual outcomes of visual discomfort reduction and protection from light damage.
In the lateral geniculate nucleus (LGN) the large neurons of the magnocellular layers are functio... more In the lateral geniculate nucleus (LGN) the large neurons of the magnocellular layers are functionally distinct and anatomically segregated from the small neurons of the parvocellular layers. This segregation of large and small cells is not maintained in the primary visual cortex (V1); instead a heterogeneous mixture of cells occurs, particularly in the output layers. Nevertheless, our results indicate that for the middle and upper layers of V1, cell size remains a predictor of physiological properties. We recorded extracellularly from neurons in V1 of alert monkeys and analyzed the amplitude, duration, and polarity of the action potentials of 199 cells. Of 156 cells that could be assigned to specific cortical layers, 137 (88%) were localized to the middle and upper cortical layers, layer 4 and above. We summarize evidence that the large-amplitude spikes are discharged by large cells, whereas small-amplitude spikes are the action potentials of smaller cells. Large spikes were predominantly negative and of longer duration, whereas small spikes were predominantly positive and briefer. The putative large cells had lower ongoing activity, smaller receptive field activating regions and higher selectivity for stimulus geometry and stimulus motion than the small cells. The contrasting properties of the large and the small cells were illustrated dramatically in simultaneous recordings made from adjacent cells. Our results imply that there may be an anatomic pairing or clustering of small and large cells that could be integral to the functional organization of the cortex. We suggest that the small and the large cells of area V1 have different roles, such that the small cells may shape the properties of the large output cells. If some of the small cells are also output cells, then cell size should be a predictor of the type of information being sent to other brain regions. Because of their high activity and relative ease of stimulation, the small cells also may contribute disproportionately to in vivo images based on metabolic responses such as changes in blood flow.
In the creation of a digital version of this manuscript, D. Max Snodderly's name was erroneously ... more In the creation of a digital version of this manuscript, D. Max Snodderly's name was erroneously reproduced as D. Ma Snodderly. The publisher would like to apologize for the error.
When we view a scene, saccades separate brief periods of fixation during which the information is... more When we view a scene, saccades separate brief periods of fixation during which the information is acquired and processed. Mounting evidence indicates that the retinal motion introduced by fixational drift enhances fine detail, but physiological studies have not analyzed its effect. Responses of visual neurons to natural images are generally studied as if the eye is stationary during fixation. One reason for this situation is the challenge of measuring ocular drift with high accuracy and precision. Here we assess precision and resolution of two eyetracking systems, an eye coil (Remmel labs EM6) and a dual-Purkinje image eyetracker, (DPI v.6), to support neural and psychophysical studies of natural images with high precision during drift periods. We examined these systems noise with a model eye and eye coil mimicking the signal from a real eye. The impact of system noise on the measurements was characterized. The optimized eye coil system with a bandpass of 0-320 Hz had an RMS noise level of 0.18&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;~0.27&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;, and the slow drift over a period of 7 min was 0.52&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; ± 0.16&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; (N=10). The RMS noise level of a DPI eyetracker was of 0.35&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; for both the horizontal and the vertical axes, and the slow drift over a period of 10 min was 0.7&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; ± 0.20&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; (N=6). By comparing the power spectrum of the system noise with ocular drift recorded from human subjects and a monkey, we determined the optimal filter to characterize drift speed. We also identified a high frequency tremor that varied between 50 and 100 Hz. Our results across the humans and the monkey consistently showed that ocular speed during fixation is much faster than previously thought, and tremor is sometimes larger than expected. These results can facilitate the development of standard procedures for optimizing study of the dynamics of microscopic ocular motion. Meeting abstract presented at VSS 2015.
To examine the association between intermediate age-related macular degeneration (AMD) and the op... more To examine the association between intermediate age-related macular degeneration (AMD) and the optical density of macular pigment (MPOD), which is composed of lutein and zeaxanthin from the diet. Design: Cross-sectional cohort study. Participants: We included 1698 of 2005 women ages 54 to 86 years and participating in the Carotenoids in Age-Related Eye Disease Study, an ancillary study of the Women's Health Initiative. Methods: The MPOD was measured noninvasively by heterochromatic flicker photometry. Fundus photographs were taken to document prevalent AMD. Main Outcome Measures: Intermediate AMD (n ϭ 305) and two subtypes-large drusen (n ϭ 233) and pigmentary abnormalities (n ϭ 157). Results: After adjusting for covariates, the odds ratio (OR) and 95% confidence interval (CI) for AMD among women in quintile (Q) 5 (n ϭ 339) versus 1 (n ϭ 340) for MPOD was 1.4 (0.9, 2.1). However, after excluding women with possible unstable diets and recent supplement use due to chronic disease history, associations reversed (OR Q2-5 vs. 1, 0.8; 95% CI, 0.5-1.2), but remained nonsignificant. Associations also differed between middle-aged (54-69 years) and older (Ն70 years) women (P-interaction ϭ 0.09), but less so, after excluding women who were likely to have unstable diets: adjusted ORs (95% CI) were 0.5 (0.3-1.0; P ϭ 0.08) for intermediate AMD among middle-aged women (n ϭ 516) with MPOD in Q2 to Q5 versus 1 and 1.0 (0.5-2.0; P ϭ 0.90) for older women (n ϭ 422). Conclusions: The MPOD is not cross-sectionally associated with AMD. The inconsistency of relationships across age groups and in subgroups of women who are likely to have more stable diets suggests that cross-sectional associations may be biased and highlights the need to study these relationships prospectively. Ophthalmology 2008;
Investigative Ophthalmology & Visual Science, Mar 28, 2013
PURPOSE. To investigate genetic determinants of macular pigment optical density in women from the... more PURPOSE. To investigate genetic determinants of macular pigment optical density in women from the Carotenoids in Age-Related Eye Disease Study (CAREDS), an ancillary study of the Women's Health Initiative Observational Study. METHODS. 1585 of 2005 CAREDS participants had macular pigment optical density (MPOD) measured noninvasively using customized heterochromatic flicker photometry and blood samples genotyped for 440 single nucleotide polymorphisms (SNPs) in 26 candidate genes related to absorption, transport, binding, and cleavage of carotenoids directly, or via lipid transport. SNPs were individually tested for associations with MPOD using least-squares linear regression. RESULTS. Twenty-one SNPs from 11 genes were associated with MPOD (P 0.05) after adjusting for dietary intake of lutein and zeaxanthin. This includes variants in or near genes related to zeaxanthin binding in the macula (GSTP1), carotenoid cleavage (BCMO1), cholesterol transport or uptake (SCARB1, ABCA1, ABCG5, and LIPC), long-chain omega-3 fatty acid status (ELOVL2, FADS1, and FADS2), and various maculopathies (ALDH3A2 and RPE65). The strongest association was for rs11645428 near BCMO1 (b A ¼ 0.029, P ¼ 2.2 3 10 À4). Conditional modeling within genes and further adjustment for other predictors of MPOD, including waist circumference, diabetes, and dietary intake of fiber, resulted in 13 SNPs from 10 genes maintaining independent association with MPOD. Variation in these single gene polymorphisms accounted for 5% of the variability in MPOD (P ¼ 3.5 3 10 À11). CONCLUSIONS. Our results support that MPOD is a multi-factorial phenotype associated with variation in genes related to carotenoid transport, uptake, and metabolism, independent of known dietary and health influences on MPOD.
Eye position of two macaques and two humans was recorded while they detected the unpredictable di... more Eye position of two macaques and two humans was recorded while they detected the unpredictable dimming of a hxation spot in a dark or a light environment. Fixational saccades often had complex waveforms that resulted from clustering of two or more saccadic displacements with no intervening drift periods. In the dark, all subjects had low frequencies of saccade clusters (0.15-0.61/set). Three of the subjects increased the frequency of saccade clusters and decreased the magnitude of the displacements when the task was performed in the normally lighted laboratory. The higher saccade frequencies in the light did not automatically result in greater dispersion of eye position. One of the humans, who had the lowest saccade frequency, was relatively unaffected by the stimulus conditions. The change in stimulus conditions had a more pronounced effect on the fixational eye movements of the macaques than the humans. In the dark, the macaques made saccades mostly down and nasal, but in the light the saccadic displacements occurred over a wider range of angular directions. Mean eye position was higher in the dark than in the light. The humans altered the direction of their saccadic displacements very little and did not change their mean eye position when they switched from a dark to a lighted environment. The influence of a lighted environment is interpreted as an interaction between foveolar and peripheral retinal inputs. The results suggest that tlxational saccades may have mom than one role, perhaps including stimulation of pathways originating in the peripheral retina. These peripheral field inputs have a stronger effect on the fixational control system of macaques than of humans. Eye movements Fixation Saccades Primates
Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye ... more Intersaccadic periods of fixation are characterized by incessant retinal motion due to small eye movements. While these movements are often disregarded as noise, the temporal modulations they introduce to retinal receptors are significant. However, analysis of these input modulations is challenging because the intersaccadic eye motion is close to the resolution limits of most eyetrackers, including widespread pupil-based video systems. Here, we analyzed in depth the limits of two high-precision eyetrackers, the Dual-Purkinje Image and the scleral search coil, and compared the intersaccadic eye movements of humans to those of a non-human primate. By means of a model eye we determined that the resolution of both techniques is sufficient to reliably measure intersaccadic ocular activity up to approximately 80 Hz. Our results show that the characteristics of ocular drift are remarkably similar in the two species and that a clear deviation from a scale-invariant spectrum occurs in the range between 50-100 Hz, generally attributed to ocular tremor. The amplitude of this deviation differs on the two axes of motion. In addition to our experimental observations, we suggest basic guidelines to evaluate the performance of eyetrackers and to optimize experimental conditions for the measurement of ocular drift and tremor.
The American Journal of Clinical Nutrition, Jun 1, 2000
Background: Lutein and zeaxanthin are the only carotenoids in the macular region of the retina (r... more 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.
In many ocular diseases the retinal thickness is altered due to edema or atrophy. We have develop... more In many ocular diseases the retinal thickness is altered due to edema or atrophy. We have developed a method to measure the retinal thickness and thus provide earlier diagnosis and improve therapy monitoring. The application in humans has provided encouraging results. (1,2) To establish the method further, comparison between in vivo and in vitro thickness measurements in the same eye are desirable. The layers from which light is reflected and detected by the in vivo method can be identified and more information about the presence of tissue distortions arising from the in vitro method during preparation can be acquired. We present the comparison between locally measured thickness values in a cynomolgus monkey and measurements made by light microscopy of the whole mounted retina.
PURPOSE. To compare action spectra for visual discomfort in the fovea and the parafovea and to de... more PURPOSE. To compare action spectra for visual discomfort in the fovea and the parafovea and to determine the effect of macular pigment (MP). METHODS. Visual discomfort thresholds to lights from 440 to 600 nm were obtained for six young (<35 y), visually normal subjects with a wide range of MP densities (0.10-0.71 at 30 0 eccentricity). Foveal and parafoveal conditions were assessed. Discomfort thresholds were also obtained for xenon-white light (partially absorbed by MP), and a broadband yellow (outside the absorption band of MP). MP was measured psychophysically using heterochromatic flicker photometry (HFP). RESULTS. For the parafovea, discomfort sensitivity (1/threshold) increased sharply with decreasing wavelength for all subjects. Commensurate with a subject's MP level, MP significantly reduced visual discomfort to short wavelengths (including xenon-white light) for central viewing. CONCLUSIONS. MP simultaneously reduces visual discomfort and protects from light damage at short wavelengths. As a result, MP increases the range of safe and comfortable light levels. Because higher light levels enable improved visual sensitivity for fine detail, these findings indicate that the spectral absorption properties and spatial distribution of MP combine to protect the retina while enhancing visual performance. The action spectrum for visual discomfort closely matches the risk for acute light damage to the retinal pigment epithelium, and it is consistent with a major influence from the intrinsically photosensitive retinal ganglion cells containing melanopsin. We suggest that MP interacts with nonimage-forming retinal input to achieve the dual outcomes of visual discomfort reduction and protection from light damage.
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