1. The Human Retina

3. Retina Function To detect movement To detect color To detect detail.

4. Retina structure The retina is an extension of the brain! The retina is made of 2 types of photoreceptors (neurons). – Rods for detecting (motion) dim light (no color) – Cones for detecting color and detail

5. Front of eye near lens (almost all rods) Sides of retina middle of eye (more rods than cones) Back/Center of retina (Macula/fovea/dark spot) only cones Optic disk (no photoreceptors – it is a blind spot)

6. The cones are fewer (only about 5% of the photoreceptors in the eye! ) 3 types of cones, each detects one color – Red – Blue – Green 125 million rods – only 6 million cones Cones need light to function Cones are not at the front of the eye, only middle and back.

7. Two spots on the retina 1 spot is the dark red macula (fovea in center) – This is where the detailed reading image of your vision straight ahead (0 to 5 degrees) is projected on your retina. 1 spot is the optic disk – This is the spot which looks bright in the picture. – It is where the optic nerve that goes to the brain attaches. – Many blood vessels come from here. – There are no photoreceptors (rods or cones) here.

8. Why don’t we see the blind spot? Our left eye sees the part that is “blind” or missing from the right eye (and vice versa).

9. Retinal imaging Retinal imaging is the shape a pattern created by the blood vessels on the retina. Each individuals retinal pattern is unique like a fingerprint. Therefore some high-security fields use retinal scans to identify people.

10. Regions of Vision Peripheral vision (180°) – outer most edges of vision – mostly motion is detected – very little color seen – almost all rods Intermediate zone – (90 ° to 120 ° ) between peripheral and straight ahead – Details are not defined – Color if light is intense – Mix of rods and cones Straight ahead – (10°) – Only cones (object falls on the macula/fovea) – Good detail – Subtle color differences detected here.

11. color blindness test