Saturday, February 24, 2007

Eye Color

Eye Color and Human Diseases


Here are some notes on possible links between the eye color and human health & performance:

Light eye colour linked to deafness after meningitis.
PMID: 11238154

Eye colour, hair colour and skin colour are important risk factors for malignant melanoma and non-melanoma skin cancers. PMID: 9602230

In this study we found significant differences in choice reaction time using the McCarthy and Donchin (1981) paradigm, the dark-eyed subjects being faster than the light-eyed. PMID: 8170759

Eye colour and susceptibility to noise-induced permanent threshold shift.257 3rd-year apprentices were given ear, nose and throat examination, electroacoustic impedance tests and audiometry. Their eye colour was also recorded. Average hearing levels of otologically normal left ears were poorer at 4 kHz (p less than 0.05) for apprentices with eye colours indicating no melanin pigmentation of the iris than for apprentices with melanin iris pigmentation.PMID: 7352922

There was a significant linear association between 20 degrees detection thresholds and eye color (r = 0.39), which was substantially improved with a two-line function (part level and part increasing linearly, r = 0.65). CONCLUSIONS: We were generally unable to demonstrate the relationship between eye color and sensitivity reported previously using a Cochet-Bonnet esthesiometer. However, for a subset of subjects with palest irises, there appears to be a linear association between eye color and sensitivity to cooling stimuli. PMID: 16044076

Human pigmentation, including eye color, has been associated with skin cancer risk. These results suggest that P gene, in part, determines normal phenotypic variation in human eye color and may therefore represent an inherited biomarker of cutaneous cancer risk. PMID: 12163334

Eye color and cutaneous nevi predict risk of ocular melanoma in Australia. Risk of choroidal and ciliary body melanoma (n = 246) was increased in people with grey (OR 2.9, 95% CI 1.5-5.5), hazel (OR 2.2, 95% CI 1.4-3.7) and blue eyes (OR 1.7, 95% CI 1.0-2.7) compared with brown eyes. Non-brown eye color was a risk factor for iris melanoma (n = 25). Eye color is the strongest constitutional predictor of choroidal and ciliary body melanoma, and may indicate a protective effect of melanin density at these sites. PMID: 11351315

Eye color and pure-tone hearing threshold. Pure-tone hearing thresholds at test frequencies, 250, 500, 1000, 2000, 4000, and 8000 Hz, were compared for 149 unambiguously blue- vs 172 brown-eyed individuals. Blue-eyed subjects ages 17 to 30 years (M = 20.3) had a significantly elevated mean hearing threshold at the highest frequency tested. PMID: 7899021

Researchers investigating performance differences between light- and dark-eyed individuals have indicated that dark-eyed individuals perform better on reactive activities than light-eyed individuals. College students (61 men, 64 women) performed a forehand rally with different colored racquetballs. Eye color, sex, and total hits were recorded for each subject. Men scored significantly better with balls of each color than did women. Dark-eyed men performed better than other subjects and performance was better with blue balls than yellow or green balls. PMID: 7808908

Eye color and hypertension Compared to persons with each lighter eye color, those with brown eyes were more prone to develop hypertension, with relative risk of 1.5 (95% confidence interval 1.18-1.96) compared to all persons with nonbrown eyes. The association persisted after control for race, sex, body mass index, alcohol use, educational level, parental history of hypertension, and among whites, for ethnic origin as crudely estimated by last name. Partial confirmation was obtained in three largely independent study groups: 1) 25 pairs of eye-color-discordant dizygotic twins; 2) 894 pairs of incident hypertensives and controls selected only with multiphasic screening blood pressure measurements; and 3) cross-sectional analysis of 152,018 multiphasic screenees. The weak association of eye color with hypertension clearly requires further confirmation. Although it has little potential for use in screening or clinical care, it may have implications regarding etiology. Areas for further exploration include the close metabolic relation of melanins to catecholamines, both derived from the amino acid tyrosine, and the possibility that dark-eyed persons react more quickly and strongly to stimuli than light-eyed persons. PMID: 2292985

Effect of eye color on heart rate response to intramuscular administration of atropine. Subjects with more pigmented irides (brown-eyed) showed a more rapid rise in heart rate compared to less pigmented irides (hazel-eyed and blue-eyed subjects). Following injection by the device with a slower atropine absorption rate, these differences were particularly enhanced and an abbreviated bradycardic phase of the heart rate response was observed for the brown-eyed subjects. This observation confirms earlier reports and suggests the possibility of an interference by melanin (in the iris or elsewhere) in atropine accessibility to selected muscarinic target sites.PMID: 3209800

The pigmentation of human iris influences the uptake and storing of zinc. Age-related macular degeneration (AMD) is more prevalent among the elderly Caucasians than in Africans. A significant association between light iris colour, fundus pigmentation and incidence of AMD is reported, suggesting a possible correlation with melanin pigment. Zinc is known to bind to melanin in pigmented tissues and to enhance antioxidant capacity by function as a cofactor or gene expression factor of antioxidant enzymes in the eye. In this in vitro study, we investigated the uptake and storage of zinc in human irides. Irides of blue and brown human eyes were used. The number of melanocytes was measured. Tissues without any treatment served as controls. The irides were incubated with 100 microM zinc chloride in culture medium for 24 h. Specimens of the tissues were stored for the uptake examination. The remained pieces were further incubated for 3 and 7 d to investigate the storage of zinc. The concentration of zinc was measured by inductively coupled plasma mass spectrometry (ICP-MS). Melanocytes count was significantly higher in the brown tissues (P < or =" 0.01)" or =" 3.0," or =" 1.5," or =" 1.1," p =" 0.05)." trend =" .001)." ratio =" 7.3;" interval =" 2.6-20.1" n =" 246)" or =" 4.1" or =" 4" or =" 3.4)," or =" 2.8)," x2 =" 15.04," p =" .02)."> 45 years, p <>age-associated increases in lens OD.PMID: 11045246

See also:

Color Atlas of the Eye in Systemic Disease
by Daniel H.,Gold and Thomas A. Weingeist (Editors)

Book Info
Univ. of Texas Medical Branch, Galveston. Combines features of a color atlas with a quick reference, tabular format. Includes most of the major and more common systemic disorders with significant ocular manifestations, along with less common ocular-systemic diseases. Abundant, high-quality color illustrations are included. DNLM: Eye Manifestations--Atlases.

Key words:
eye color, eye colour, diseases, health, performance, deafness, malignant melanoma, non-melanoma skin cancer, hearing levels, sensitivity to cooling stimuli, ocular melanoma, hearing threshold, reactive activities, hypertension, rise in heart rate, macular degeneration.

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