As we learned more about genetics and cell chemistry, it was determined that melanin, a brown pigment, is controlled by the brown-blue gene on chromosome 15 and the green-blue gene on chromosome 19. This model has repeatedly been shown to be wrong, yet is still presented as an explanation for eye color. Based on the color of the mother and father's eyes, little Johnny or little Jill would have blue or brown eyes. This model promoted the notion that blue eye color is a simple recessive trait. Many of us learned in school the so-called simple Mendelian, or "two gene" genetic model to predict eye color. This results in a brown ring around the pupil, which can look quite unusual in an otherwise “blue” eye. Sometimes, the pigment from the back surface “rolls” up onto the front surface right at the pupil border. There's a rare genetic condition called albinism in which those individuals do not have pigment on the back of the iris and their iris color appears pink. The red color interacts with the blues and browns to create aqua and violet iris colors. This is also what causes the red reflex in the iris pupil seen in photographs taken with a flash. The retina reflects red from the network of blood vessels contained within its structure. Although the majority of irises have similar pigment density on the back surface (called the iris pigment epithelium), some people have less and that allows for some reflection from the retina in the back of the eye.
The size and spacing of the fibers and stromal cells determines the "blueness" or "greenness' of the reflected light. The light interacts with the gray iris fibers and the iris stromal cells and reflects as blue.
Sometimes there is little or no pigment on the front surface. If the iris contains pigment on both the front and back surface, the incident light that reflects off the iris is brown. The hole in the middle is called the pupil and it changes size to regulate the amount of light entering the eye. The iris is located inside the eye, between the cornea (front most surface) and the internal crystalline lens. How much do we really know about eye color?Įye color is determined primarily by the concentration and distribution of melanin pigment on the iris fibers. Many children a born with non-descript gray eyes and some become blue, some brown. There's also gray, "hazel", a mixed brown/green/blue, golden brown or amber, even violet. These are the "standard" eye colors, but we've all seen people with even different eye colors. The information is presented here to educate and inform and to guide you to an understanding of cause, prevention as well as treatment.īrown eyes, blues eyes, and green eyes. The reader should regularly consult a physician in matters relating to his or her health and particularly with respect to any symptoms that may require diagnosis or medical attention. PLEASE READ THIS: The information contained herein is not intended as a substitute for medical advice and care from qualified, licensed health care providers. This is a really great site that calculates percentage wise the eye color of your potential children. What Color Eyes Would Your Children Have? Children & Understanding Family Building.Building Family Through Embryo Donation.
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