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22 Cards in this Set

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  • Back
Name the times when to use a trial frame.
Pediatrics, Geriatrics, Non-ambulatory, pt's with head tilts, low vision, new Rx, new presbyopes, prism Rx, broken phoropter, high refractive Rx
What is a Distometer and how is it important?
It is an instrument that measures vertex distance and is important because with high Rx (+/- 6.00D), vertex distance changes the Rx more.
Janelli clips/Halberg clips are used to perform what duties?
Fit over patient's glasses and ensure vertex distance. Can place trial lenes in the slots available. 3 for Janelli and 2 for Halberg
What is the best and most flexible starting point for the trial frame refraction?
Durign the monocular subjective refraction, what is the point of finding the best spehere and performing the MPMVA?
To determine the JND (just noticable difference) = smallest amount of change needed to differentiate variation in blur
If pt's VA is 20/100 what is the JND and what lenses are used to adjust the shere power?
JND is 1.00 and the lenses used are +/-0.50D.
If during the shere adjustment the pt likes the plus lens addition, what lens power is placed in the lens bank? example of +/-0.50D.
If pt likes +0.50D JND is 1.00D and you place +1.00 in the bank,
If new VA is 20/60, what is the JND and what lenses should be used next to adjust the power?
JND = 0.6 and lenses used should be +/-0.50D
On the hand held JCC and Phoropter JCC what do the red dots represent?
Minus Cylinder AXIS
Name the steps in order for hand held JCC versus in-phoroter JCC
Power acceptance, axis refinment, power refinment; the steps are the same for in-phoropter
While adjusting the cylinder power, for every 0.50 change in cylinder, how much change must occur in the shpere?
what is performed after the JCC in a trial frame refraction?
2nd best sphere, VA's, and balance (performed the same way if done behind a phoropter)
What tests can be performed with trial frames?
ANY out-of-phoropter tests where the patient needs best VA.
What is the purpose of the stenopaic slit refraction?
Determines the required correction for each major meridian individually.
For what patients would this technique be more useful?
irregualr astigmatism, large astigmatism, reduced VA, bad responders
Optically speaking why does the slit aid in the visual acuity?
It reduces the blur circles in the perpendicular meridian.
The axis of the stenopaic slit when best acuity is reachedis also known as the...
minus cylinder axis
The meridian the runs parallel to the slit and is the location of hte best visual acuity corresponds to what lens power? (sphere or cylinder)
How do you determine the sphere power?
It is the resultant power of the lens rack and the fogging lens
After changing the slit to the meridian of worst acuity and reducing the fog to MPMVA, what value have you found?
the algebraic difference between the lens in place at the end and the beginning is the minus cylinder power
Example problem: with +1.00D fogging lens pt reports best VA with slit at 135. Fogg reduced by -2.25 with ret bars; what is the sphere power of this lens?
-1.25D @135
same example: slit rotated to worst acuity @45, fog reduced to -2.75D. What is the lens power in this meridian and what is the pt's final Rx.
With +1.00 fogging still in place the algebraic difference with -2.75 is -1.75D @45. Pt's Rx will be -1.25 -0.50 X135