R R

What Are Melanin Granules (Iris)?

Melanin granules in the iris are pigment-containing structures, often melanosomes, found in iris cells that store melanin. They help determine iris color and reduce stray light by absorbing light within the eye. Iris pigment is concentrated in both the iris stroma and the iris pigment epithelium on the back surface of the iris. When pigment granules are released abnormally, they can deposit in the front of the eye and sometimes affect eye pressure.

Link to This Resource Page

Provide a valuable resource to your clients or customers by linking to this resource page. Just place the following link on your website.

To display this...

What Are Melanin Granules (Iris)?

Melanin granules in the iris are pigment-containing structures, often melanosomes, found in iris cells that store melanin. They help determine iris color and reduce stray light by absorbing light within the eye. Iris pigment is concentrated in both the iris stroma and the iris pigment epithelium on the back surface of the iris. When pigment granules are released abnormally, they can deposit in the front of the eye and sometimes affect eye pressure.

read more about melanin granules iris ...

Copy this HTML:

Copy HTML Copied!

What Melanin Granules Do

  • Absorb light to reduce glare and internal light scatter
  • Support image quality by limiting stray reflections inside the eye
  • Contribute to iris color based on pigment amount and distribution

Where Iris Pigment Comes From

Iris color and pigment patterns depend on melanin amount, how pigment is packaged, and where it is distributed in the iris. The iris pigment epithelium is heavily pigmented in most people, while the stroma varies more and strongly influences visible eye color. In lighter eyes, stromal pigment is lower and light scattering plays a larger role in appearance. Genetics and age can influence these patterns over time.

When Pigment Granules Are Seen in Eye Exams

Clinicians may observe pigment granules in the anterior chamber or deposited on structures if pigment has been released from the iris. A classic example is pigment dispersion, where pigment from the posterior iris can circulate and deposit on the corneal endothelium or in the drainage system. Pigment can also be seen after trauma, certain surgeries, or inflammation. Eye pressure checks and angle evaluation help determine whether pigment is affecting outflow.

Conditions Linked to Iris Pigment Release

  • Pigment dispersion syndrome and pigmentary glaucoma
  • Trauma-related pigment release
  • Inflammation that disrupts iris pigment epithelium integrity
  • Post-surgical pigment changes in selected cases

FAQs on Iris Melanin Granules

Do melanin granules determine eye color?

Yes, largely. The amount and distribution of melanin in the iris stroma strongly affects visible eye color, while the iris pigment epithelium is typically densely pigmented. Light scattering also contributes to how eye color appears, especially in lighter eyes.

What is pigment dispersion syndrome?

Pigment dispersion syndrome occurs when pigment granules are released from the posterior iris pigment epithelium and disperse within the front of the eye. The pigment can deposit on the cornea, iris, lens, and trabecular meshwork. Some people later develop elevated eye pressure or pigmentary glaucoma.

Can pigment granules raise eye pressure?

Yes. If pigment accumulates in the trabecular meshwork, it can reduce aqueous outflow and raise intraocular pressure in some eyes. Not everyone with pigment release develops glaucoma, but monitoring is important when pigment dispersion is present.

Can iris pigment change over time?

It can. Subtle changes may occur with age, medications, inflammation, trauma, or certain eye conditions. Noticeable or rapid changes should be evaluated by an eye care professional to rule out disease.

References

Pigment Dispersion Syndrome. StatPearls (NCBI Bookshelf). https://www.ncbi.nlm.nih.gov/books/NBK580526/. Date Accessed February 9, 2026.

Biochemistry, Melanin. StatPearls (NCBI Bookshelf). https://www.ncbi.nlm.nih.gov/books/NBK459156/. Date Accessed February 9, 2026.

Oculocutaneous Albinism and Ocular Albinism Overview. NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK590568/. Date Accessed February 9, 2026.

Cyclodestructive Procedures: Types and Techniques. American Academy of Ophthalmology (EyeNet). https://www.aao.org/eyenet/article/cyclodestructive-procedures-types-and-techniques. Date Accessed February 9, 2026.

Melanin in the Retinal Epithelium and Magnetic Sensing. MDPI. https://www.mdpi.com/2673-4125/4/4/30. Date Accessed February 9, 2026.