Eye Anatomy

Eye Structure enclosed and cushioned by fat and walls of bony orbit

filled with fluid = humors composed of 3 layers = tunics filled with fluid = humors to maintain shape lens for focusing divides eye into anterior and posterior chambers

3 Layers: Tunics

1. Fibrous Tunic outermost 2 parts sclera “white of the eye” Tough Anchors muscles

1. Fibrous tunic 2 parts Sclera 2. Cornea “clear window” lacks blood vessels easy to transplant nutrition via diffusion from aqueous humor - fluid behind

2. Vascular Tunic 3 regions middle choroid (coat) vascular pigmented posterior part absorbs light and prevents scattering

2. Vascular Tunic 3 regions choroid ciliary body encircles lens made of smooth muscle - ciliary muscles controls lens shape

2. Vascular Tunic 3 regions choroid ciliary body folds secrete aqueous humor - ciliary processes suspensory ligaments hold lens up

2. Vascular Tunic 3. iris visible colored area contain melanin amount and distribution = different colors

2. Vascular Tunic 3. iris made of muscles that control pupil size - regulating light pupil is hole in center of iris

pupillary reflex also responds to interests or emotions appealing subject matter, problem solving = dilates boredom or repugnant material = constriction of pupil

3. Sensory tunic = retina 2 layers outer is pigmented to absorb light inner layer transparent photoreceptor neurons (rods and cones)

Detached Retina separation of pigmented from transparent Warning signs include: seeing many new flashing lights showers of many floaters blurred vision a curtain-like blockage  

3. Sensory tunic = retina optic disc where optic nerve leaves eye Fovea optic disc where optic nerve leaves eye “blind spot” off center optic nerve has blood vessels in center

Photoreceptors Rods dim light black and white just outside fovea peripheral vision

Photoreceptors Cones bright light color vision Optic Disc concentrated in center fovea centralis

nervous flow is opposite (→ = light) light → ganglion cells → bipolar neurons → photoreceptors→ back up and to optic nerve

Chambers and Humors

Posterior Chamber with Vitreous Humor transmits light supports back surface of lens supports eye shape vitreous humor thick and clear lasts a lifetime

Anterior Chambers with Aqueous Humor chamber between cornea and lens formed in ciliary processes watery constantly produced and drained via canals of Schlemm

Glaucoma if canals are blocked unable to drain

Glaucoma if canals are blocked unable to drain = nerve cells gradually destroyed by pressure treated with drugs

Lens

Lens biconvex transparent flexible becomes less elastic with age

Cataracts lens clouding