How many layers are in the retina?

• A. 8
• B. 9
• C. 11
• D. 10

Answer: (D)

The retina is organized into a set of distinct layers that reflect how visual information is processed and transmitted. In standard histology and exam references, there are ten layers described in the retina and its boundary structures. Moving from the inner to the outer surface, these are the nerve fiber layer, the ganglion cell layer, the inner plexiform layer, the inner nuclear layer, the outer plexiform layer, the outer nuclear layer, the external limiting membrane, the photoreceptor layer (inner and outer segments considered together in many texts), the retinal pigment epithelium, and the adjacent Bruch’s membrane. Counting these gives ten. Some diagrams differ by how they group the photoreceptor segments or whether Bruch’s membrane is included as part of the retinal layers, which can shift the count to nine or eleven, but ten is the usual number tested.