Normal retina, ophthalmoscope image. The retina is the light-sensitive membrane that lines the back of the eye. Blood vessels (red) radiate out from the optic disc (yellow, centre). The optic disc is the area where the optic nerve and blood vessels enter the eye. Due to this, it has no light- sensitive cells, and is the cause of the blind spot. The dark red area at centre is the macula. This is the region of the retina with the highest concentration of light-sensitive cells, and is responsible for the sharp vision at the centre of the visual field.