Disorders of the eyelids and optic globe (conjunctiva, cornea, and uvea)

Intraocular pressure (glaucoma) Lens (cataract) Vitreous humor and retinas Dual pathways and visual cortex Extraocular muscles and eye

movement

Sclera Outer supporting layer

Choroid Middle vascular layer

Retina Composed of the neuronal retinal layer and

the outer pigmented layer

Visual receptor function of the eyeball The optic nerve Visual pathways that carry and

distribute sensory information from the optic glove to the CNS

Primary and visual association cortices that translate the sensory signals into visual images

Description A hollow spherical structure that functions

in the reception of the light rays that provide the stimuli for vision

Mechanism of vision The refractive surface of the cornea and

accommodative properties of the lens focus the light signals from near and far objects on the photoreceptors in the retina

Palpebrae Modified folds of skin that protect the

eyeball Palpebral fissure

The oval opening between the upper and lower eyelids

Canthus Found at the corners of the eye, where the

upper and lower lids meet

Tarsus (plate of dense connective tissue) Gives the lid its shape Contains modified sebaceous glands,

called meibomian glands, the ducts of which open onto the eyelid margins

Seborrheic form Usually associated with seborrhea (i.e.,

dandruff) of the scalp or brows Staphylococcal blepharitis

May be caused by Staphylococcus epidermitis or S. aureus

The lesions are often ulcerative

Major lacrimal gland Produces the tears

The puncta and tear sac Collect the tears

Nasolacrimal duct Empties the tears into the

nasal cavity

Conjunctivitis Infectious conjunctivitis

Bacterial conjunctivitis Viral conjunctivitis Chlamydial conjunctivitis Ophthalmia neonatorum

Allergic conjunctivitis

An extremely thin outer epithelial layer Continuous with the

bulbar conjunctiva A middle layer called

the substantia propria or stroma Composed of regularly

arranged collagen bundles embedded in a mucopolysaccharide matrix

An inner endothelial layer Lies next to the aqueous

humor of the anterior chamber

Corneal trauma (image 1)

Keratitis (image 2)

Herpes simplex keratitis (image 3)

Abnormal corneal deposits Arcus senilis (image 4)

Controls the size of the pupil Is controlled by the autonomic nervous

system The parasympathetic nervous system

controls pupillary constriction The sympathetic nervous system controls

pupillary dilation

The aqueous humor Serves to maintain the intraocular pressure

and Provides for the nutritive needs of the lens

and posterior cornea Mediates the exchange of respiratory gases Contains a low concentration of protein and

high concentrations of ascorbic acid, glucose, and amino acids

Definition An optic neuropathy characterized by optic

disk cupping and visual field loss Causes

An increase in intraocular pressure that results from abnormalities in the balance between aqueous production and outflow

Most common cause is an interference with aqueous outflow from the anterior chamber, rather overproduction of aqueous humor

Seeing through glaucoma patients’

eyes

Angle-closure (narrow-angle) vs. open-angle (wide-angle) Depends on location, circulation, and

resorption Congenital vs. acquired condition Primary vs. secondary disorder

Primary: no evidence of preexisting ocular or systemic disease

Secondary: results from inflammatory processes affecting the eye, tumors, or blood cells of trauma-produced hemorrhage

Excessive lacrimation and photophobia Affected infants tend to be fussy, have

poor eating habits, and rub their eyes frequently

Diffuse edema of the cornea usually gives the eye a grayish-white appearance

Enlargement of the entire globe (buphthalmos)

The lens is an avascular, transparent, biconvex body, the posterior side of which is more convex than the anterior side

A thin, highly elastic lens capsule is attached to the surrounding ciliary body by delicate suspensory radial ligaments called zonules, which hold the lens in place

When changing lens shape, the tough elastic sclera acts as a bow, the zonule and the lens capsule act as the bowstring

The suspensory ligaments and lens capsule are normally under tension, causing a flattened shape for distant vision

Contraction of the muscle fibers of the ciliary body produces a more spherical or convex shape for near vision

Hyperopia or farsightedness The anterior-posterior

dimension of the eyeball is too short, the image is focused posterior to (behind) the retina

Myopia or nearsightedness The anterior-posterior

dimension of the eyeball is too long, the focus point for an infinitely distant target is anterior to the retina

See what they see...

Refers to changes in vision that occur because of aging

Cataract Lens opacity that

interferes with the transmission of light to the retina

The most common cause of age-related visual loss in the world

Effects of aging Genetic influences Environmental and metabolic

influences Drugs Injury

Definition A colorless, amorphous biologic gel that fills

the posterior cavity of the eye Composition

Approximately 99% water, some salts, glycoproteins, proteoglycans, and dispersed collagen fibrils

Location Attached to the ciliary body and the

peripheral retina in the region of the ora serrata and to the periphery of the optic disk

Receive visual images Partially analyze them Transmit this modified information to

the brain

Three layers of neurons A posterior layer of photoreceptors A middle layer of bipolar cells An inner layer of ganglion cells that

communicate with the photoreceptors

Rods, capable of black–white discrimination

Cones, capable of color discrimination

Ischemia of the retina Papilledema Central Retinal Artery Occlusion Central Retinal Vein Occlusion

Diabetic retinopathy Hypertensive retinopathy Atherosclerosis of retinal vessels Retinopathy of prematurity

‘Dry” form An atrophic non-exudative

“Wet” form Exudative

Visual field defects Retinal defects

Disorders of the optic pathways Disorders of the Visual Cortex

Amblyopia A condition of diminished vision in which no

detectable organic lesion of the eye is present

Strabismus Any abnormality of eye coordination or

alignment that results in loss of binocular vision

Paralytic strabismus Non-paralytic strabismus

Innervated by three cranial nerves The abducens nerve (CN VI) innervates

the lateral rectus The trochlear nerve (CN IV) innervates

the superior oblique The oculomotor nerve (CN III)

innervates the remaining four muscles