Refraction Flashcards
After VA failed we check for __(3)__ one after the other (as each fails), and add __(2)__.
Counting fingers (CF) and specify distance--> Hand motion (HM) --> Light perception (LP). We add Sine Correction (SC) or Cum Correction (CC).
Light perception (LP) can be subdivided to__(3)__.
LPC (creta) - specify direction of light.
LPC (increta) - can’t specify the direction of light.
NLP - no light perception (totally blind)
Diopter equals___
Give examples of negative and positive.
Diopter = 1/focal point
\+5 = 1/0.2 -10 = 1/-0.1
What is the focal point?
distance from the lens to a specific point (in meters). Positive after the lens, and negative before it.
Diopter - The stronger the lens the______.
shorter the distance (more refraction).
Cylindrical lens allows______
only light form a specific axis to refract onto the retina
_____ released by a signal from _____cells encourages the eye to grow in size.
Acetylcholine
Amacrine cells
Atropine caused the children receiving it a _________
Halt in eye growth.
Hypermetropia is______
small eye due to sharp acuity at too early
Accommodation ability is______ related to age.
inversely
A 10 y.o. can accommodate +14
A 30 y.o. can accommodate +8
Accommodation ability decrease with age is due to _____
and not_______
Elasticity decrease and size increases of the lense, and not ciliary muscle weakness.
checking for hyperopia requires_____
paralysis of the ciliary muscle.
Explain PRK (Photo-Refractive Keratectomy).
removal of epithelial lining -> polishing stoma -> epithelial lining grows back (after 3 days). Safer but painful.
Explain LASIK - (laser-assisted in situ keratomileuses).
100 um flap (from epithelial lining and stoma)is cut->polishing stoma -> flap is placed back (no influence to the power of the cornea). No pain and immediate results, but a higher chance of complications.
Refractive surgery - cant leave a cornea at less than _____um
300
