Iris photography helps separate pigment from pathology, ophthalmic imager says | AAO 2026

Color alone cannot tell a clinician whether a spot on the iris is harmless pigment or a sign of disease—the way an eye is lit and photographed over time often makes the difference, Kathleen Warren, OCT-C, CPT, said during an educational session at the annual meeting of the American Academy of Ophthalmology (AAO) held Oct. 9 through Oct. 12, 2026, in New Orleans.

Warren is the senior ophthalmic photographer at Massachusetts Eye and Ear at Massachusetts General Hospital. She presented ‘Iris Color, DNA and Genetics: The Thumbprints to the Soul,’ which began with a volunteer portion in which attendees had the opportunity to have their iris photographed and examined for added context.

Following this, the session began in earnest, as Warren walked attendees through the basics of iris anatomy, the genetics of eye color and the lighting techniques imaging staff use to document disease.

Where eye color comes from

Iris color is shaped by the amount of melanin in the iris, the structure of the stroma and the way light scatters through it, Warren said. Blue eyes, for example, contain no blue pigment. The color is an optical effect that occurs when the anterior stroma holds less melanin and lets more light in.

Eye color is also polygenic, Warren said, which means the simple model of dominant brown and recessive blue taught in school does not explain the full range of shades seen in clinic. Pigment level has practical consequences as well. Patients with darker irises take longer to dilate, she said, while lighter irises respond to dilating drops quickly.

Lighting reveals what the eye hides

“Sometimes you can’t see pathology just looking at a patient’s eye, so that’s where we come in with the lighting,” Warren said.

Direct illumination shows the eye straight on, and diffuse lighting softens harsh reflections. Retroillumination, which bounces light off the back of the eye through a dilated pupil, can expose areas where the iris has thinned. Specular lighting highlights reflective surfaces and contours. During the session’s hands-on workshop, lighting from the side allowed the group to capture a clear, unpigmented strand of tissue moving in a volunteer’s anterior chamber. To judge whether an iris freckle, also called a nevus, is flat or elevated, imagers can use a gonioscopy lens to look into the curvature of the eye.

Separating normal variation from disease

“A color alone is never a diagnosis,” Warren said. Heterochromia, sectoral color differences and freckles can all be normal variation, but imaging staff should note whether a spot is elevated, whether there is more than one, and whether its size, shape or location has changed.

Pathologic findings Warren described included inflammation such as uveitis, atrophy, unexpected vessels feeding tissue that should not be there, pupil shape changes after trauma or surgery and pigment that may originate from a choroidal melanoma at the back of the eye. She also recalled a patient who developed endophthalmitis after an intraocular injection. The eye was bloodshot and cloudy, and what initially raised concern as an abnormal growth turned out to be infection at the injection site.

During the question-and-answer period, Warren explained the eyes can offer clues to conditions elsewhere in the body, citing high cholesterol as one that can appear as a ring in the eye. Ophthalmic photography also supports patients after vision loss. For scleral shell prostheses, Warren said, iris photographs must be precise so the prosthetic could be painted to match closely enough that others could not tell the difference.

Documentation as a clinical tool

Repeat imaging lets clinical teams track a lesion across visits and communicate concerns, Warren said.

“Photographers sometimes get that we're at the bottom of the totem pole, but a lot, if not all, the information we provide, is what helps the doctors see the changes over time,” Warren said. “Don't ever take for granted what we do for people every day. The details you capture might change everything.”