eye anatomy and sight L9pt3

Innermost layer: Retina
- Delicate membrane lining the posterior segment.
- Contains photoreceptors: rods (sensitive to light, help with low-light vision) and cones (color vision).
Optic Nerve: Transmits electric signals to the brain from photoreceptors.
- Optic Disc / Blind Spot: Area without photoreceptors where optic nerve exits the eye.
Lens:
- Clear, flexible structure behind the iris and pupil.
- Focuses light onto the retina.
- Must be transparent for proper function.

Anterior Cavity (Segment):
- Contains aqueous humor (clear watery liquid).
- Secreted by ciliary processes, provides nutrients, oxygen, and maintains intraocular pressure.
- Drained through scleral venous sinus (canalis Schlemm).
Posterior Cavity (Segment):
- Contains vitreous humor (jelly-like substance).
- Supports posterior lens surface and holds retina in place.

Light Reception: Light rays enter through the pupil, focused by the lens onto the retina.
Retinal photoreceptors convert light to electric signals sent to the brain.

Rods:
- Cylinder-shaped, assist in low-light/night vision, peripheral vision, and produce indistinct images in shades of gray.
Cones:
- Cone-shaped, enable color vision in bright light.
- Types: respond to blue, green, and red light.
- Concentrated in macula lutea; highest in fovea centralis for high-acuity color vision.

Light consists of energy packets traveling in wave-like fashion, visible at 400-700 nanometers.
Focusing requires bending (refraction) through cornea, lens, and vitreous humor.
Image formed on retina is upside down and reversed; brain interprets this.

Normal Eye: Able to see at or beyond 20 feet (20/20 vision).
Depth Perception: Created by both eyes viewing from different angles; absence of this leads to 2D vision.