Test- Ch. 25-26 Flashcards
Hyperopia
If the distance between the lens and retina is too short, the light rays focus behind the retina.
This causes difficulty in seeing objects close at hand and is called farsightedness (hyperopia).
Myopia
If the opposite is true and the eyeball is too elongated, the light rays will converge and focus in front of the retina.
The individual then has difficulty seeing objects at a distance and is referred to as being nearsighted. Nearsightedness is called myopia.
Accommodation
accomplished by ciliary muscles and ligaments that change the shape of the lens, making it more rounded or flatter, thereby allowing light rays to fall on the retina.
Presbyopia
With increasing age, the ciliary muscles become less elastic and cannot readily accommodate the needs of distant and near vision.
Hardening of the ciliary muscles occurs in many people older than 40 years and is known as presbyopia.
Bifocal eyeglasses are usually prescribed for this condition because they allow for two sets of lenses in one pair of eyeglasses, one for viewing distant objects and one for seeing close objects.
Astigmatism
a visual defect that results from warped lens or an irregular curvature of the cornea.
What does astigmatism prevent?
The horizontal and vertical rays from focusing at the same point on the retina.
What happens when there is a serious error of refraction?
The eye will tire easily or the person will have defective vision because the eye cannot change the shape of the lens enough to compensate for the abnormality
What is the treatment for astigmatism?
Treated with prescription eyeglasses or contact lenses that are fitted so that the light rays are brought into proper focus on the retina.
Refractive surgery permits the correction of refraction problems for some people.
Nearsighted (myopic) can undergo one of three procedures: PRK, Lasik, or Smile.
What is Photorefractive Keratectomy (PRK)
An excimer laser is used to remove a thin layer of tissue from the cornea that corrects the excessive curvature of the cornea that is interfering with the proper focus of light rays through the lens.
Takes 30 minutes and start to see improvement within 3 to 5 days.
What is Laser-Assisted in Situ Keratomileusis (LASIK)
Used to treat nearsightedness
The Middle layer of the cornea is reshaped with a laser after a very thin outer layer of the cornea is peeled back.
The outer layer is replaced.
Takes 10 to 15 minutes per eye and is performed as an outpatient procedure.
What is small incision lenticule Extraction (Smile)
A laser procedure in which the cornea is reshaped by the excision of a small piece of corneal tissue, correcting myopia.
What is Uveitis?
The uveal tract consists of the iris, the ciliary body, and the choroid. Uveitis is the inflammation of the uveal tract.
What are the causes of Uveitis?
Herpes virus
Syphilis
Cytomegalovirus
Toxoplasmosis
Tuberculosis
West Nile virus
S/s of Uveitis
Tearing
Blurred vision
Photophobia
Aching around the eye
A bloodshot sclera
A small, nonreactive, irregular pupil
Treatment of Uveitis
Involves resting the ciliary body with a cycloplegic drug.
The pupil is dilated to prevent adhesions of the involved structures.
Analgesics, antibiotics, and oral or ocular steroid therapy may be used.
Cool or warm compresses are used for discomfort.
Sunglasses should be worn to reduce photophobia.
Low light indoors is advisable.