Vision Correction Flashcards
Methods of Correcting vision problems
- corrective lenses
- contact lenses
- surgical correction
- nutrition
Refraction def
bending of light rays as they pass from one transparent medium through another of different density
Myopia
-corrective lens type
concave spherical, minus and divergent
Hyperopia
-corrective lens type
convex, plus and convergent
Astigmatism
-corrective lens type
-corrected w/ spherical lens
Myopia & astigmatism
-corrective lens type
Hyperopia & astigmatism
-lens type
- concave divergent and spherical lens
- convex converging and spherical lens
Refractive Keratoplasty
- what is this?
- types
generic term that includes all surgical procedures on the cornea to improve vision by changing the shape, and thus the refractive index of the corneal surface.
- Keratotomies= corneal incisions
- keratectomies= removal of corneal epithelium
- keratomileusis= reshaping a stromal layer of the cornea.
Patient Selection of Surgery
- general CI
- autoimmune, collagen vascular and immunodeficiency disease affect corneal healing
- pregnant women/nursing (must wait 1 year after breastfeeding)
- pts w/ abnormal wound healing (keloids
- Diabetes Mellitus (can perform if well controlled, without cataract or diabetic retinopathy)
Patient Selection of Surgery
-Ocular CI
- keratconjunctivitis sicca (really really dry eyes)
- exposure keratitis
- neurotrophic kerratitis
- lid disorder affecting tear layer
- patient w/ hx of herpetic keratitis
- pt w/ abnormal cornea
- severe rosacea
*essentailly if you have
Radial Keratotomy
- first commonly used for what vision correction
- what is this procedure?
- first commonly practiced in myopia, though not used much anymore.
- incision created produce bulge in peripheral portion of cornea which flattens the central cornea. Done in both eyes, wait 6wks in-between.
LASIK
- what does this stand for?
- corrects which type of vision
- explain this procedure.
- compare to PRK (photorefractive keratotomy)
laser in-situ Keratomileusis
- myopia and hyperopia, astigmatism
- uses excimer laser to resect corneal flap and then either steepen(hyperopia) or flatten a too steep cornea(myopia), return original corneal flap.
- similar to PRK except corneal epithelium remains intact
- much faster recovery
Disadvantages & Advantages to LASIK
- changes made to cornea are irreversible.
- technically complex
- can rarely cause a loss of best vision (which is best corrected vision with glasses or contacts)
- costs $500-1000
- 90% will have desired vision
- very little pain
- vision corrected nearly immediately
- no bandages/stiches
- adjustments can be made years after
SE of LASIK
- discomfort
- glare
- see halos around images
- difficulty driving at night
- fluctuating vision
- dry eyes
Photorefractive Keratoectomy (PRK)
- what type of vision correction?
- describe procedure.
- compare to LASIK
- circumstances in which this procedure is preferred
- myopic, hyperopic, astigmatism
- laser removes part of outside cornea, reshaping the eye to correct refractive errors.
- recovery is longer and more painful than LASIK, longer to see final results
- when pt have thin or irregular shaped corneas or evidence of scarring
LASEK
- describe procedure
- advantages
- disadvantages
- cut thin corneal flap. few drops of 20% alcohol solution instilled and left on cornea for 30seconds, this is washed and dried. eximer laser treats the stroma just like in LASIK
Advantages:
- thinner corneal flap may avoid corneal ectasia
- LASIK requires more complicated equipment
- risk of infection are easier to manage with thinner flap.
Disadvantages:
- thin corneal flap may dislodge post-op causing greater pain
- slower optical recovery time
- can cause stromal haze in treated myopic pt
