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Melanocytes and iris color. Electron microscopic findings
P D Imesch1, C D Bindley, Z Khademian
1Department of Ophthalmology and Visual Sciences, University of Wisconsin, Madison, USA.
Archives of Ophthalmology (Chicago, Ill. : 1960)
|April 1, 1996
Summary
Iris color differences are linked to the amount and area of melanosomes in superficial melanocytes. These findings quantify pigment variations, explaining diverse iris hues.
Area of Science:
- Ophthalmology
- Cell Biology
- Genetics
Background:
- Iris color is a complex trait influenced by melanin pigment.
- Previous studies have suggested a link between iris color and melanosome content, but quantitative data is limited.
Purpose of the Study:
- To quantitatively correlate iris color with the pigment content of melanocytes.
- To investigate the role of melanosome characteristics in determining iris pigmentation.
Main Methods:
- Autopsy eyes were categorized by iris color (blue, hazel, brown, or with a peripupillary ring).
- Electron microscopy and computerized image analysis were used to measure melanosome area, number, and size in superficial stromal melanocytes.
- Measurements focused on melanosomes within the perinuclear and/or peripheral cytoplasmic areas.
Main Results:
- Significant differences in average melanosomal area per perinuclear cytoplasmic area (AMAC) and average number of melanosomes per perinuclear area (AMNC) were observed across iris color groups (P<.001).
- A notable distinction was found between blue irises and other color groups.
- While melanosome size did not vary significantly, AMAC and AMNC showed trends correlating with iris color, particularly a ringed pattern.
Conclusions:
- Variations in AMNC and AMAC within superficial iris melanocytes contribute to the observed differences in iris color.
- This study provides quantitative evidence linking melanosome characteristics to iris pigmentation, offering insights into the biological basis of eye color.