sensory disorders Flashcards
are the 4 eye functions that provides clear images and vision (4)
- refraction
- pupillary constriction
- accommodation
- convergence
refraction
bends light rays from the outside into the eye through curved surfaces and refractive media and finally into the retina
pupillary constriction
- constriction and dilation control the amount of light that enters the eyes
accommodation
allows the healthy eye to focus images sharply on the retina whether the image is close to the eye or distant
convergence
- ability to turn both eyes inward toward the nose at the same time
coordinated eye movements ensure?
- both eyes receive an image at the same time so only a single image is seen
muscles around the eye are innervated by
cranial nerves 3 (oculomotor), 6 (trochlear), and 11 (abducens)
the optic nerve (CN 2) is
nerve of sight, connecting the optic disc to the brain
the trigeminal nerve (CN 5)
stimulates the blink reflex when the cornea is touched
the facial nerve (CN 7) innvervates
lacrimal glands and muscles for lid closure
assessment of the the eyes include: (2)
- assess muscle function (eyes will NOT turn to a particular position if the muscle is weak or if the controlling nerve is affected)
- vision testing: visual acuity tests to measure both distance (snellen eye chart) and near vision (rosenbaum pocket vision screener) -> findings recorded as a comparision between what the patient can read at 20 feet and the distance that a person with normal vision can read that the same time
ex:
- 20/50 means that the patient sees at 20 feet from the chart what a healthy eye sees at 50 feet
age related changes for vision (5)
1) arcus senilis
2) presbyopia
3) ectropion
4) clarity and shape of the cornea change with age (cornea flattens, curve of its surface becomes irregular, this change worsens with astigmatism and blurred vision)
5) iris has less ability to dilate, which leads to difficulty in adapting to dark environments
arcus senilis
an opaque, bluish white ring within the outer edge of the cornea, caused by fat deposits (will look like blue eyes)
presbyopia
- near objects, especially reading material must be placed farther from the eye to be seen clearly (bifocals)
ectropion
- the lower eyelid may relax and fall away from the eye, leading to dry eye manifestations
refraction
bending of light rays for the ability of the eye to focus images on the retina and depends on the length of the eye from front to back and the refractive power of the lens system
types of refraction (4)
1) emmetropia
2) hyperopia
3) myopia
4) astigmatism
emmetropia
perfect refection of the eye in which light rays from a distant source are focused into a sharp image on the retina
presbyopia (what, as a result, begins in)
age related problem in which the lens loses its elastricity and is less able to change shape to focus the eye for close work
- as a result, images fall behind the retina (hyperopia)
- begins in people in their 40s
hyperopia (farsightedness) (what, s/sx, tx)
- occurs when the eye does not refract light enough, as a result, images actually converge behind the retina
- s/sx: distant vision is normal, near vision is POOR
- tx: corrected with a convex lens in eyeglasses or contact lenses
tips: difficulty driving/reading, can see far away, reading glasses
myopia (nearsightedness) (what, s/sx, tx)
- occurs when the eye over bends the light and images converge in front of the retina
- s/sx: near vision is normal, distance vision is POOR
- tx: corrected with a biconcave lens in eyeglasses or contact lenses (LASIK)
astigmatism (3)
- refractive error caused by unevenly curved surfaces on or in the eye, especially of the cornea
- these uneven surfaces distort vision
- d/t light rays are not refracted equally in all directions, the image does not focus on the retina
refractive errors nursing interventions (3)
- eyeglasses
- contact lenses
- last in-situ kertamileusis (LASIK) surgery or photorefractive keratectomy (PRK): both procedures correct nearsightedness, farsightedness, and astigmatism, powerful laser pulses reshape the deep corneal layers
extra:
- side effects: halos, glares (decreased visual acuity)
- meds: corticosteroids, NSAIDs, antibiotics
blindess
having best corrected visual acuity that can range from 20/400 to no light perception
- legally defined by visual acuity with corrective lenses is 20/200 or less in the better eye or if the visual field is 20 degrees or less
- blindness can occur in one or both eyes
blindness nursing interventions (5)
- communication
- safety
- ambulation
- self care
- support
glaucoma
group of eye disorders resulting in increased OP (intraocular pressure)
- tissues damage starts in the periphery and moves inward toward the fovea centralis
IOP
normal IOP requires a balance between production and outflow of aqueous humor
- if IOP becomes too high, the extra pressure compresses retinal blood vessels and photoreceptors and their synapsing nerve fibers
- this compression results in poorly oxygenated photoreceptors and nerve fibers
- these sensitive nerve tissues become ischemic and die. when too many have died, vision is lost permanently
what is normal IOP when aqeuous fluid production and drainage are in balance
10-21 mmhg
primary open angle glaucoma (POAG) (3)
- wide angle glaucoma
- most common form of primary glaucoma, outflow of aqeuous humor through the chamber angle is reduced
- usually affects both eyes and has no manifestations in the early stages
primary angle closure glausoma (PACG) (3)
- acute glaucoma or narrow angle glaucoma
- forward displacement of the iris, which presses against the cornea and closes the chamber angle, suddenly preventing outflow of aqueous humor
- sudden onset, EMERGENCY
glaucoma s/sx angle closure glaucoma (6)
- severe pain in the eye or forehead
- redness
- decreased or blurred vision
- seeing halos or rainbows
- headache
- N/V
glaucoma s/sx open angle glaucoma (3)
- early manifestations: none, painless
- loss of peripheral vision
- halos
glaucoma nursing interventions (pharm (5), surgery (2))
pharm:
- prostaglandins agonists drugs: reduce IOP by increasing aqueous humor outflow
- adrenergic agonists, beta adrenergic blockers: reduce IOP by limiting the production of aqueous humor and by dilating the pupil
- cholinergic agonists: reduce IOP by increasing the outflow of the aqueous humor
- carbonic anhydrase inhibitors: directly and strongly inhibit production of aqueous humor
- systemic osmotic drugs may be given for angle closure glaucoma to rapidly reduce IOP (oral glycerin, IV mannitol)
surgery:
- shunts, implants (helps aqueous humor to flow)
cataract (what, s/sx (4))
lens opacity that distorts the image
- both eyes may have cataracts, but the rate of progression in each eye is different
s/sx:
- early manifestations: slightly blurred vision, decreased color perception
- blurred vision
- double vision
- opacity: prevents light from producing images
cataracts nursing interventions (3, post surgery (4))
- prevention: smoking cessation, weight reduction, optimal blood sugar control, sunglasses, etc.
- promote safety and independence
- surgery when symptoms interfere with ADLs (cataract removal surgery -> outpt.)
post surgery:
- educate on the importance of close adherence to the eye drop regimen after surgery
- wear a light eye patch at night to prevent accidental rubbing
- assess for signs of infection
- remind the patient to avoid activities that might increase IOP
macular degeneration
deterioration of the macula (area of central vision)l with the most common type being the age related macular degeneration (AMD)