Anatomy & Physiology of The Eye

The Visual System

Eyes Accessory structures Sensory neurons

Eyes Action potentials Brain

Action potentials convey the visual information from the eyes to the brain.

Visual input(Ex. reading words and numbers, light vs. dark, movement, color)

Accessory Structures of the Eye Eyebrows

Eyelids

Accessory Structures of the Eye Conjunctiva

Lacrimal Apparatus

Accessory Structures of the Eye Extrinsic Eye Muscles

Accessory Structures of the Eye….

Eyebrow

Eyelid

Accessory Structures of the Eye….

Conjunctiva

Accessory Structures of the Eye….

Lacrimal Apparatus

Accessory Structures of the Eye….

Extrinsic Eye Muscles

INTRODUCTION

The human eye is an organ that reacts to light allowing vision.

Vision is by far the most relied on / used of the five sense.

More than 70% of the information receive consists of visual information

Orbit

The orbit is the bony socket of the skull. The eye is cushioned within orbit by pads of fat. It also contains the muscles that move the eye, blood vessels and nerves.

The orbit also contains the lacrimal gland that is located underneath the outer portion of the upper eyelid.

The lacrimal gland produces tears that lubricate and moisten the eye, which may flush any foreign matter. Tears drain away from the eye through the nasolacrimal duct, located in the inner corner of the eye

Eyelids and Eyelashes

Both help protect the eye from foreign matter.

The eyelids also help spread tears over the surface of the eye.

The eyelids also prevent incoming light that may damage the eye.

Conjunctiva contains blood vessel that are visible against the white

background of the sclera. Prevents bacteria and other foreign bodies from getting

to the back of the eye.

Anterior Chamber fluid-filled (Aqeuous Humourso funny~) space immediately

behind the cornea. the aqeuous humour huehuehue helps nourish the cornea

and the lenses. For refractive index n=c/vo

Maintains intraocular pressure Presence of immunoglobulins indicate role in immune

response

Posterior Chamber Contains aqueous humour

Fovea It is a small, central pit composed of closely

packed cones. Responsible for sharp central vision Point of maximum visual acuity

Macula An oval-shaped pigmented area near the

center of the retina. Contain the fovea and foveola Absorbs excess blue and UV light.

Vitreous Cavity The vitreous cavity is located behind the lens

and in front of the retina. It is filled with a gel-like fluid, called the vitreous humour.

The vitreous humor helps maintain the shape of the eye.

Lens A clear, flexible structure that is located just

behind the iris and pupil. A ring of muscular tissue, called the ciliary

body, surrounds and is connected to the lens by zonules (of Zinn).

help control fine focusing light into the retina

Iris the coloured part of the eye Controls the amount of light that enters the

eye by acting as a diaphragm; Contains muscles around the:

Pupil -which constricts/dilates during

increased/decreased illumination Anterior Chamber

Located where the cornea meets the iris The Trabecular Network is where the

aqueous humour drains out of the eye

“Tunica”

Three Tunics Fibrous Tunic (tunica fibrosa occuli)

Sclera Cornea

Vascular Tunic (tunica vasculosa occuli) / Uvea Choroid Ciliary Body Iris

Nervous Tunic (Retina) (tunica interna) Aqeous Humour Vitreous Body Lens

Fibrous Tunic

Sclera hard, dense, firm that maintains the form of

the bulb. Opaque; the white part of the eye. extraocular muscles are attached to

sclera. These muscles pull on the sclera when looking in different directions.

Cornea transparent. A clear dome over the iris. Helps focus light as it enters the eye. * this is where contact lenses rest on.

VASCULAR TUNIC / UVEA

Composed of: Iris Ciliary body Choroid

Functions to: Produce aqueous humour Accommodation Holding the lens in place

Ciliary Body Produces aqueous humour accomodation:

ciliary muscles contract = makes lens more convex -> focus on closer objects

Ciliary muscles relax = flattens lens -> focus on farther objects

Choroid Layers of blood vessels located between the

sclera and the retina Provide nourishment to the back of the eye Contains melanin that can limit uncontrolled

reflection within the eye that may distort images.

Nervous Tunic / RETINA

The retina acts like the film in a camera to create an image.

When focused light strikes the retina, chemical reactions occur within specialized layers of cells.

These chemical reactions cause electrical signals, which are transmitted through nerve cells into the optic nerve, which carries these signals to the brain, where the electrical signals are converted into recognizable images.

Photoreceptors: cones cones cones… rods rods rods…

Rods more sensitive to light Allow vision in low light situations Used in peripheral vision Concentrated on the outer edges of the

retina Cones

less sensitive to light Allows to see colours

Find your Blind Spot!~

Functions of the eye

- Light refraction

- Focusing images on the retina The cornea is a convex structure and as light rays pass from the air through the cornea, they converge.

Chambers of the eye

- Anterior and posterior chambers are filled with aqueous humor which helps maintain pressure within the eye, refracts light. If flow through venous ring is blocked, pressure in the eye increase resulting to glaucoma.

- Vitreous chamber holds the lens and the retina in place but unlike the aqueous humor it doesn’t circulate.

Pathway

Color blindness

Color blindness is the absence of perception of one or more colors. Color perception may be decreased or completely lost. The loss may involve perception of all three colors or of one or two colors. Most forms of color blindness occur more frequently in males and are x linked genetic.