Sensory Flashcards
refraction
Bends light rays from the outside into the eye through curved surfaces and refractive media and finally to the retina
pupillary constriction
Constriction and dilation control the amount of light that enters the eye
Accommodation
Allows the healthy eye to focus images sharply on the retina whether the image is close to the eye or distant
Convergence
The ability to turn both eyes inward toward the nose at the same time
Coordinated eye movements ensure that both eyes…
eyes receive an image at the same time so only a single image is seen
The muscles around the eye are innervated by cranial nerves
III oculomotor
IV trochlear
VI abducens
the optic nerve II is
the nerve of sight, connecting the optic disc to the brain
the trigeminal nerve V stimulates
the blink reflex when the cornea is touched
the facial nerve VII innervates
the lacrimal glands and muscles for lid closure
Vision testing:
visual acuity tests to measure both distance (using the Snellen eye chart) and near vision (using the Rosenbaum Pocket Vision Screener)
Record findings as a comparison between what the patient can read at 20 feet and the distance that a person with normal vision can read the same line
Arcus senilis
an opaque, bluish white ring within the outer edge of the cornea, is caused by fat deposits
presbyopia
near objects, especially reading material must be placed farther from the eye to be seen clearly
age-related problem which the lens loses its elasticity and is less able to change shape to focus the eye for close work
ectropion
the lower eyelid may relax and fall away from the eye, leading to dry eye manifestations
structural changes occur with aging including…
decreased eye muscle tone that reduces the ability to keep the gaze focused on a single object
how does the clarity and shape of the cornea change with age
The cornea flattens, and the curve of its surface becomes irregular. This change causes or worsens astigmatism and blurs vision
with age, the iris has less ability to dilate which…
which leads to difficulty in adapting to dark environments
emmetropia
is the perfect refraction of the eye in which light rays from a distant source are focused into a sharp image on the retina
Hyperopia (farsightedness)
occurs when the eye does not refract light enough; as a result, images actually converge behind the retina
hyperopia signs and symptoms
Distant vision is normal
Near vision is poor
hyperopia treatment
Corrected with a convex lens in eyeglasses or contact lenses
Myopia (nearsightedness)
occurs when the eye overbends the light and images converge in front of the retina
myopia signs and symptoms
Near vision is normal
Distance vision is poor
myopia treatment
Corrected with a biconcave lens in eyeglasses or contact lenses
Astigmatism
is a refractive error caused by unevenly curved surfaces on or in the eye, especially of the cornea. These uneven surfaces distort vision
Because light rays are not refracted equally in all directions, the image does not focus on the retina
Astigmatism nursing interventions
Eyeglasses
Contact lenses
Laser in-situ keratomileusis (LASIK) surgery or photorefractive keratectomy (PRK)
Both procedures can correct nearsightedness, farsightedness, and astigmatism
Powerful laser pulses reshape the deeper corneal layers
blindness
is 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
can occur in one or both eyes
blindness nursing interventions
Communication
Safety
Ambulation
Self-care
Support
glaucoma is
a group of eye disorders resulting in increased IOP (intraocular pressure)
a normal IOP requires a…
balance between production and outflow of aqueous humor
if the 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
Tissue damage starts in the periphery and moves inward toward the fovea centralis
When aqueous fluid production and drainage are in balance, the IOP is between 10 and 21 mmHg
Primary open-angle glaucoma (POAG)
also known as wide angle glaucoma; is the most common form of primary glaucoma; outflow of aqueous humor through the chamber angle is reduced
Usually affects both eyes and has no manifestations in the early stages
Primary angle-closure glaucoma (PACG)
also known as acute glaucoma or narrow angle glaucoma; is a forward displacement of the iris, which presses against the cornea and closes the chamber angle, suddenly preventing outflow of aqueous humor
Has a sudden onset and is an emergency
angle-closure glaucoma signs and symptoms
Severe pain in the eye or forehead
Redness
Decreased or blurred vision
Seeing halos or rainbows
Headache
N/V
open-angle glaucoma signs and symptoms
Early manifestations:
None
Painless
Loss of peripheral vision
Halos
glaucoma nursing interventions
Pharmacological
Prostaglandins agonists drugs reduce IOP by increasing aqueous humor outflow
Adrenergic agonists and 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 and IV mannitol
Surgery