Refractive Errors Flashcards
What are refractive errors?
Refractive errors are a common cause of impaired vision.
How are refractive errors corrected?
Refractive errors can often be corrected with glasses.
What is hyperopia?
Hyperopia is when the eye is too short for refractive power of the cornea and lens resulting in light focused behind the retina. Often referred to as farsightedness. Patients can see better at a distance compared to up close.
What is myopia?
Myopia is when the eye is too long for refractive power of the cornea and lens resulting in light focused in front of the retina. It is often referred to as nearsightedness. Patients can see better up close than at a distance.
What is astigmatism?
Astigmatism is when there is abnormal curvature of the lens resulting in different refractive power at different axes.
What is presbyopia?
Presbyopia is age-related impaired accommodation (focusing on near objects). It primarily results from decreased lens elasticity. Presbyopia often necessitates reading glasses.
If patients have vision less than 20/20, what does improvement of vision when looking through a pinhole indicate?
Improvement of vision while looking through a pinhole indicates that spectacles will improve vision.
How is hyperopia corrected?
A convex lens will correct hyperopia.
How is myopia corrected?
A concave lens will correct hyperopia.
What are 3 common problems with wearing contact lenses?
- Corneal abrasions
- Irritation of the upper palpebral conunctiva
- Infected corneal ulcers
What are 3 types of refractive surgery?
- Laser in situ keratomileusis (LASIK)
- Photorefractive Keratectomy (PRK)
- epi-LASIK
What is Lasik Surgery?
Lasik surgery involves creating a flap of epithelium, Bowman’s membrane, and stroma using a laser. A different laser, called an excimer, is used to ablate and thin the underlying stromal bed.
What are disadvantages of LASIK?
- Resulting decrease in ocular rigidity.
- Damage to corneal nerve fibers results in dry eyes
- epithelilization under the corneal flap
What is photorefractive keratectomy (PRK)?
PRK eliminates a need for a flap by mechanically creating a central corneal abrasion to remove the epithelium.
What is the advantage of PRK?
It leaves more functional stroma.
