In which retinal location is the internal limiting membrane (ILM) not present?

In which retinal location is the internal limiting membrane (ILM) not present?

• A. Fovea
• B. Macula
• C. Peripheral retina
• D. Optic disc

Answer: (D)

The inner limiting membrane is the basement membrane produced by Müller cells that lines the inner surface of the retina, forming the boundary between retina and vitreous. It is present across most of the retina, including the fovea, macula, and peripheral retina. At the optic disc, however, the retina ends and the optic nerve fibers exit the eye, so there is no continuous Müller-cell–derived surface to form an inner limiting membrane. The boundary at the optic disc is provided by other tissues as the nerve fibers pass through, not by the ILM. That’s why the ILM is not present at the optic disc.

The inner limiting membrane is the basement membrane produced by Müller cells that lines the inner surface of the retina, forming the boundary between retina and vitreous. It is present across most of the retina, including the fovea, macula, and peripheral retina. At the optic disc, however, the retina ends and the optic nerve fibers exit the eye, so there is no continuous Müller-cell–derived surface to form an inner limiting membrane. The boundary at the optic disc is provided by other tissues as the nerve fibers pass through, not by the ILM. That’s why the ILM is not present at the optic disc.