Vision

Lacrimal Apparatus:

1. What: Tear gland and multiple ducts that drain tears into the nasal cavity

2. Function: Cleanse and lubricate the eye surface, protect from infection, deliver oxygen/nutrients to the conjuctiva

Tunic 1: Outer Fibrous Area

1. Sclera

   1. What: White of eye

   2. Function: Protective cover and attachment of muscles to move it

2. Cornea

   1. What: Anterior, transparent region

   2. Function: Transmits light to eye

Tunic 2: Middle Vascular Layer

1. Uvea

   1. What: Contains iris, choroid, and ciliary body

2. Choroid

   1. What: Vascular, pigmented layer behind retina

   2. Function: Vessels provide oxygen, nutrients, and waste-removal for outer layer of retina

3. Ciliary Body

   1. What: Extension of choroid to form muscle ring around lens

   2. Function: Supports iris and secretes aqueous humor

4. Iris:

   1. What: Color part of eye/adjustable

   2. Function: Support pupil

5. Pupil:

   1. What: Black dot of eye

   2. Function: Opening to eye

6. Chromatophores

   1. What: Pigments in the eye that give it color

Tunic 3: Inner Eye

1. Retina

   1. What: The layer of photoreceptor cells

   2. Function: Detect light and convert it into neural signals.

2. Optic Disc

   1. What: The point where the optic nerve exits the eye, leading to a temporary blind spot in the visual field.

   2. Function: Transmit visual information from the retina to the brain for interpretation.

3. Optic Nerve

   1. Function: Carries the electrical impulses generated by the retina to the visual cortex.

Optic Components

1. Aqueous Humor

   1. What: The clear fluid that fills the space between the cornea and the lens

   2. Function: Maintains intraocular pressure and provides nutrients to the avascular structures.

2. Posterior Chamber

   1. What: Between iris and lens

3. Anterior Chamber

   1. What: Between iris and cornea

4. Lens:

   1. What: Many compacted lens fibers

5. Suspensory Ligaments

   1. What: Ring of fibers behind the pupil

   2. Function: Attaches lens to ciliary body

6. Vitreous Body:

   1. What: Jelly thats fills the vitreous chamber behind lens

   2. Functions: Keeps the eye’s intraocular pressure, supports circle shape, allows muscles to move the eye without squishing it

Neural Components

1. Retina

   1. What: Part of the brain

2. Optic Disc

3. Ora Serrata

   1. What: The part of the eye where the optic nerve exits, known for lacking photoreceptors.

Image Formation

1. Pupillary Constrictor  

   1. What: Smooth muscle encircling eye, stimulated by parasympathetic nervous system

   2. Function: Narrows pupil to admit less light to eye

2. Refraction:

   1. What: Bending of light rays

Near Response: Close-range vision adjustment

1. Convergence of Eyes

   1. Both eyes orient in the same direction

   2. Diplopia

      1. Double vision resulting from one eye’s muscle being weaker than the other

2. Pupil Constriction

   1. Causes focus on nearby objects

3. Accommodation of Lens

   1. Accommodation

      1. Change in lens curve to focus on nearby object

   2. Near Point of Vision

      1. The closest an object can be without appearing blurry

Retina

Pigmented Retina Layer

1. Contains stray light

2. Stray light doesn’t reflect back to degrade image

Neural Retina Layer

1. Photoreceptor Cells

   1. Reabsorb light to create a chemical/mechanical signal

   2. Rods

      1. Shape: Resemble a wrapped stack of coins

      2. What: Contain visual pigment rhodopsin

      3. Function: Scotopic/Night vision and Monochromatic/Grey shade vision

   3. Cones

      1. What: Contain visual pigment photopsin

      2. Function: Photopic/Day vision and Trichromatic/Color vision

   4. Bipolar cells

      1. What: First-order neurons of visual pathway

      2. Function: Synapse with rods and cones then with ganglion cells

   5. Ganglion Cells

      1. What: Largest neuron in retina/form optic nerve/ contain sensory pigment melanopsin

      2. Function: Absorb light, transmit signals to brainstem nuclei for pupillary diameter control and circadian rhythm