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19 Cards in this Set
- Front
- Back
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if corneal astigmatism is 2-2.50 DC what type of lenses are needed? |
Bi toric GP lenses |
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what type of lenses are most effective in ATR astigmatism? |
aspheric GP lenses |
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how do you correct residual astigmatism that cant be corrected w/ soft toric lenses? |
with a FRONT surface toric GP lens, as long as the corneal astig < refractive astig. |
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how does the topographer work? |
it uses the placido disk as a target to determine the surface irregularity. its a serioes of circles that when reflected in the cornea can tell the machine if the lines are more seperate or close together which is then interpreted as a change in the curvature of the cornea. |
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if you had to correct irregular astigmatism would you use soft lenses or RGP lenses? |
RGP lenses bc of the tear lens power, that corrects the irregularity |
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describe keratoconus |
progressive condition caused by the thining of the corneal stroma. asymmetric- one eye is more advanced bilatera 96% of the cases non inflammatory stops by itself eventually bc the cornea as it ages it becomes stiffer. |
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What lenticular lens design should be used for prescriptions of -1.75- -4.75? |
NO LENTICULAR LENS NEEDED |
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what lenticular lens design does a -5.00 lens need? |
a PLUS lenticular lens used for ALL negative lenses OVER -5.00D |
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on which rx would you use a NEGATIVE lenticular lens? |
for ALL positive lenses and negative lenses up to -1.50 |
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what effect is induced when a myope converges for a near object? |
a BI effect on a hyperope its a BO effect |
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on a myope if a BI effect is induced how does the obj look? |
FARTHER away on a hyperope its a BO effect so the obj looks CLOSER |
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on a refractive ametrope the relative spectacle mag will be? |
similar to the spectacle mag |
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on an axial ametrope the relative spec mag will be |
different from then spectacle mag |
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between an IOL vs. specs vs. CL which one causes LESS MAGNIFICATION? |
the IOL bc its located at the entrance pupil |
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how much would the CRA be if fitting a spherical RGP will compromise vision? |
if its more than -0.75 if the CRA is small and at 180 then the flexure of an RGP will correct the CRA or reduce it |
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if you increase 0.50 mm of optic zone diameter you have to |
flatten the base curve radious by 0.25 (add +0.25) and viceversa steepen the bcr by adding -0.25 |
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what happens if you increase the base curve radious? |
you flatten the power |
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which lens stabilization method is best for WTR asig? |
prism ballast |
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which lens stabilization method is best for ATR asig? |
thin zones acuvue oasys uses this |
