Photons not absorbed by the outer segments are mostly absorbed by which retinal layer?

• A. Inner nuclear layer
• B. Ganglion cell layer
• C. Nerve fiber layer
• D. Retinal pigment epithelium (RPE)

Answer: (D)

Light is mainly captured by the photoreceptor outer segments, but any photons that slip past are absorbed by the retinal pigment epithelium. The RPE is a pigmented layer right behind the photoreceptors and contains melanin that soaks up stray light, preventing backscatter that would blur vision. This absorption helps improve image contrast and protects photoreceptors. Beyond absorbing light, the RPE supports vision by recycling visual pigments and renewing outer segments, but its role as a light sink is why photons not captured by the outer segments end up there. The deeper neural layers—the inner nuclear layer, ganglion cell layer, and nerve fiber layer—are involved in processing and transmitting signals rather than absorbing light.