chapter 54 ppt
DESCRIPTION
N315 Pathophysiology PPT chapter 54TRANSCRIPT
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