eye anatomy

located in the frontal bone of skull, formed by 7 bones: frontal, sphenoid, ethmoid, superior maxillary, zygomatic, lacrimal and palate

bony orbit

cavity which houses the eye, lined with fatty tissue for cushion, Rim is thicker for protection of the eye

bony orbit

each muscle is associated with one primary movement, functions to move the eye in various directions and helps focus them together

extrinsic muscles

what are the 4 rectus muscles

superior, inferior, lateral, medial

what are the 2 oblique muscles

superior, inferior

thin, transparent mucous membrane that lines the eyelids

conjunctiva

• 2 muscular fibrous folds in front of each orbit

• protects the globe and eye from light, injury, dust

• distributes lacrimal secretions

eyelids

inner and outer corner of eye where eyelids meet

canthus

small, pink tissue mass at inner corner

lacrimal caruncle

produces and secretes tears thru a series of ducts into the conjunctival sac

lacrimal apparatus

secretes tears

lacrimal gland

12 separate ducts that carry tears from inner canthus to the lacrimal sac

lacrimal ducts

opening of duct

lacrimal punctum

large opening at the upper end of the nasolacrimal duct, drains into the nose

lacrimal sac

• fine, transparent membrane covering the front of eyeball (anterior)

• joins the sclera at the limbus

cornea

• 5 layers-some inner layers do not regenerate if damaged

• window of the eye, allows light rays to pass to retina

cornea

• encompasses the back ¾ of eyeball (posterior)

• made of collagenous fibers and fascia

• opaque, white

• extension of the cornea

• provides support to the eye

sclera

middle layer

• contains many blood vessels

• main source of eye nourishment

• prevents reflection of light within eyeball

choroid

middle layer

• extension of the choroid layer

• muscle tissue

• forms the aqueous humor

• affects accommodation (focusing) of eye

ciliary body

middle layer

• lies in front of the lens and behind the cornea

• colored part of the eye

• composed of muscle tissue

• radial and circular fibers

• regulates amount of light entering eye

Iris

middle layer

• opening in center of iris

• dilates and constricts

pupil

inner layer

• where the optic nerve enters the eye (blind spot)

optic disc

inner layer

• yellow spot in center of retina

• area of highest resolution and central vision

macula

tiny, depressed area containing only cones

fovea centralis

inner layer

• thin, transparent, many layered membrane

• photoreceptive layer of eye

• rods and cones

• sensory neurons

• nerve fibers converge to become the optic nerve

• responds to light energy-receives images and sends to brain via optic nerve

retina

• greatest refractive power of all the eye structures

• bends light rays-affects visual acuity

• variations in curve of cornea affects visual acuity

cornea

nearsighted

myopic

farsighted

hyperopic

• lies in front of the iris (anterior)

• filled with aqueous humor

anterior chamber

drains excess fluid into the venous system

canal of schlemm

when the duct doesn’t work, fluid backs up, results in increased pressure in eyeball which can lead to blindness

glaucoma

• suspended behind the iris and connected to the ciliary body by zonular fibers

• clear-surrounded by a capsule

lens

reflects light to retina

accommodation

cells compress and harden with age, become cloudy and opaque

cataract

• sometimes called vitreous humor

• transparent, gelatinous mass

• composed of 99% water, 1% collagen, and hyaluronic acid

• fills the posterior 4/5th of eyeball

• adheres to the retina

• maintains shape of eyeball

vitreous body (posterior chamber)

right eye

OD

left eye

OS

both eyes

OU

diagnose glaucoma by measuring the amount of pressure needed to flatten a portion of the cornea

applanation tonometry

specialized computerized tests used to create a “map” of the curvature of the cornea or surface of the retina, can show distortions of the surface of the eye, such as swelling and scarring, astigmatism

corneal and retinal topography

evaluate the blood circulation in the retina, useful in helping diagnose diabetic retinopathy, retinal detachment, and macular degeneration

fluorescein angiogram

drops in the eye that cause the pupil to dilate

dilated pupillary exam

determines your eyeglasses prescription

refraction

looks at the eye with a microscope shining a beam of light shaped like a small slit on the eye, helps to diagnose cataracts, glaucoma, retinal detachment, macular degeneration, injuries to cornea, dry eye disease

slit-lamp exam