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22 Cards in this Set
- Front
- Back
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Name the times when to use a trial frame.
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Pediatrics, Geriatrics, Non-ambulatory, pt's with head tilts, low vision, new Rx, new presbyopes, prism Rx, broken phoropter, high refractive Rx
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What is a Distometer and how is it important?
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It is an instrument that measures vertex distance and is important because with high Rx (+/- 6.00D), vertex distance changes the Rx more.
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Janelli clips/Halberg clips are used to perform what duties?
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Fit over patient's glasses and ensure vertex distance. Can place trial lenes in the slots available. 3 for Janelli and 2 for Halberg
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What is the best and most flexible starting point for the trial frame refraction?
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Retinoscopy
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Durign the monocular subjective refraction, what is the point of finding the best spehere and performing the MPMVA?
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To determine the JND (just noticable difference) = smallest amount of change needed to differentiate variation in blur
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If pt's VA is 20/100 what is the JND and what lenses are used to adjust the shere power?
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JND is 1.00 and the lenses used are +/-0.50D.
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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.
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If pt likes +0.50D JND is 1.00D and you place +1.00 in the bank,
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If new VA is 20/60, what is the JND and what lenses should be used next to adjust the power?
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JND = 0.6 and lenses used should be +/-0.50D
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On the hand held JCC and Phoropter JCC what do the red dots represent?
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Minus Cylinder AXIS
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Name the steps in order for hand held JCC versus in-phoroter JCC
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Power acceptance, axis refinment, power refinment; the steps are the same for in-phoropter
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While adjusting the cylinder power, for every 0.50 change in cylinder, how much change must occur in the shpere?
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0.25D
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what is performed after the JCC in a trial frame refraction?
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2nd best sphere, VA's, and balance (performed the same way if done behind a phoropter)
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What tests can be performed with trial frames?
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ANY out-of-phoropter tests where the patient needs best VA.
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What is the purpose of the stenopaic slit refraction?
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Determines the required correction for each major meridian individually.
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For what patients would this technique be more useful?
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irregualr astigmatism, large astigmatism, reduced VA, bad responders
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Optically speaking why does the slit aid in the visual acuity?
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It reduces the blur circles in the perpendicular meridian.
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The axis of the stenopaic slit when best acuity is reachedis also known as the...
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minus cylinder axis
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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)
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Sphere
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How do you determine the sphere power?
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It is the resultant power of the lens rack and the fogging lens
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After changing the slit to the meridian of worst acuity and reducing the fog to MPMVA, what value have you found?
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the algebraic difference between the lens in place at the end and the beginning is the minus cylinder power
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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?
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-1.25D @135
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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.
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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
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