by Juan Ding, OD, PhD
I want to tell another story of pigment… in the back of the eye. A bit like the previous post, but no one has poor vision this time and it’s all happy… at least till now.
You know you can tell if a person is white or black or Asian or Hispanic usually by their appearance, right? A large part is the difference in skin color- no brainer here. But do you know that eye doctors can tell the racial differences by the color of the retina? Like the skin and iris (blue or brown eyed), the retina, the tissue in the back of the eye, is also lined by pigment cells that show different amounts of pigment. Similar to skin color, white people typically have less pigment in their retina, which shows up more pinkish in color compared to those of darker colors, eg, Asians. However, most of the time, the two eyes will be identical in coloration. So this lady’s eyes are really unique.
I first met her a few years ago, a healthy middle aged white female interested in new glasses and contact lenses. Her vision was normal and eyes healthy in every aspect, except when I looked at her retina with a lighted magnifier, I felt very confused. Her right and left retinas looked like they belonged to two different people- the right one being very light, just like from a typical white person, but her left retina looked much darker, as if she were Asian (Figure 1). I checked everywhere and both retinas looked completely healthy. There was absolutely nothing wrong with the retinas, just with different shades of pigment. This almost felt like a person had two arms or legs of different skin tones and that is not commonly seen unless a tanning session was done only on one side of the body.
Though everything looked normal, I did refer her to a retinal specialist.
She came back next year with a diagnosis of ocular melanocytoma in the left eye.
This is a condition that usually looks like this (Figure 2a) or this (Figure 2b). It’s typically a cluster of pigment cells forming a defined area of pigmentation that can be easily identified.
In my patient’s case, her pigment cells are diffused and dispersed, with almost no visible clumps, that it looks natural, smooth and just belongs. There is also no other pigment difference between the two eyes, including on eyelids, conjunctiva and iris. The secret only lies behind the eyes, unrevealed by a dilated retinal exam.
I think it’s marvelous that a pigment disorder turns out just right for her. It’s as beautiful as those people who have different eye colors, iris heterochromia (Figure 3), but it’s well hidden and more mysterious.