What is the main component and organization of the iris stroma?

• A. Loose connective tissue with melanocytes and vasculature
• B. Dense collagen with few cells
• C. Smooth muscle bundles
• D. Elastic cartilage

Answer: (A)

The iris stroma is a loose connective tissue layer behind the anterior border layer, organized as an open, wavy network that contains melanocytes, fibroblasts, extracellular matrix, and a rich supply of blood vessels. This loose arrangement allows diffusion of nutrients and provides space for the vascular network that powers rapid changes in the iris in response to light and autonomic signals. Melanocytes within the stroma contribute to iris color, with higher pigment making the eye darker. While smooth muscle fibers of the dilator and sphincter are associated with the iris and interspersed within the tissue, they are not the main constituent; the stroma’s defining feature is its loose connective tissue with pigment cells and vessels, not dense collagen, elastic cartilage, or primarily muscle.