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Contacts Test 4
| Question | Answer |
|---|---|
| Light refracts first through the contact lens and then through the ____________? | lacrimal lens |
| How is the lacrimal lens formed? | The tears collected between the back of the CL and the front of the eye. |
| The spectacle Rx is a combination of the....? | Contact lens power + lacrimal lens power |
| What is the lacrimal lens equal to...? | The difference between the Ks |
| What is the first thing to do when finding the power? | Put the spectacle Rx in minus cylinder form |
| When do you compensate for vertex distance in contact fitting? | When the prescription is 4.00 D or greater |
| What does SAM stand for? | Steeper Adds Minus |
| What does FAP stand for? | Flatter Add Plus |
| What is the first thing you do to find the base curve? | Determine the flat K |
| What are the three different ways to fit contacts? | On K, steeper than K (STK), flatter than K (FTK) |
| When fitting flatter or steeper than K what power is corrected? | Only the sphere power |
| When fitting flatter or steeper than K, you are accommodating for the _____, and the effective sphere power....? | accommodating for the tears; effective spherical power stays the same |
| What is residual astigmatism? | difference between the refracted astigmatism and corneal astigmatism |
| What causes residual astigmatism? | internal or lenticular astigmatism |
| How is residual astigmatism found? | refracted astigmatism - corneal astigmatism = residual astigmatism |
| Anytime corneal astigmatism is greater, the residual will be a plus or minus? | plus |
| For every 0.25D change in K's the radius of curvature changes approximately ____ mm? | 0.05 |
| For every 0.50D change in K's the radius of curvature changes approximately ___ mm? | 0.10 |
| How are rigid lenses packaged? | dry in a flat pack |
| How are the lenses cleaned? | with 2-4 drops of Boston cleaner; using pinky rub from center to the outer edge (not in circles) flip over, clean the other side; hold lens and rinse with saline or water; pat dry |
| If lenses are being dispensed to the patient they are stored in...? | Boston conditioning |
| What is verified and inspected on the rigid lenses? | Base curve; power; diameter; POZ width; PPC width; bifocal seg height; center thickness; blends; edge contour; surface quality |
| What is used to verify base curve? | radiuscope; radius gauge; microspherometer; contactoguage; attachment to keratometer (con-ta-check) |
| What are two other names for the base curve? | radius of curvature; central posterior curve |
| What is used to measure the power of the lens? | Lensometer (vertometer; focimeter; lensmeter) |
| What is BVP? | Back vertex power |
| What is FVP? | front vertex power |
| When measuring BVP, what side of the lens is towards the lens stop? | concave side |
| When measuring FVP, what side of the lens is towards the lens stop? | convex side |
| Which side will measure more plus, BVP or FVP? | BVP |
| What is used to measure diameter? | diameter gauge (slot gauge, v-groove); measuring magnifier (monocular magnifier, measuring loupe); shadowgraph (projection magnifier) |
| What is used to measure the posterior optical zone width? | measuring magnifier and shadowgraph |
| What is used to measure the posterior peripheral curve width? | measuring magnifier and shadowgraph; if you have a light blend you can measure PPC and PIC; if you have med or heavy blend, you won't be able to tell the difference |
| What is used to measure the bifocal seg height? | measuring magnifier and shadowgraph |
| Where is the seg height measured? | from the truncated part of the lens to the top of the seg |
| What is the center thickness measured with? | Thickness gauge (dial gauge); attachment to the radiuscope |
| What is used to inspect and analyze the blends? | profile analyzer and fluorescent light (fluorescent tube). |
| What are you looking for when inspecting the blends? | The reflection of light on the lens to make a J or ski-edge |
| When using the fluorescent light to inspect the blends the light must be where in relation to the examiner? | in front of and higher than the examiner |
| What is used to check the edge contour and finish? | measuring magnifier; shadowgraph; lens on finger using slit lamp |
| What are you looking for when checking edge contour? | Edge shouldn't be too thick or too thin, and should be smooth and clear |
| What is used to check the surface quality of the lens? | Measuring magnifier; shadowgraph; slit lamp |
| What are you looking for when checking the surface quality? | nice clear lens with no lathe marks or scratches |
| What does an orange peel effect mean when inspecting surface quality? | The lens was not polished enough |
| What does a black dot on a lens mean? | Right eye |
| What is fenestration? | a hole (or many holes) in the lens to get more oxygen |
| What does ANSI stand for? | American National Standards Institute |
| What is ANSI? | A non-governmental, national organization that has standards that are recommendations not requirements |
| The ANSI standards are a guideline, and your standards can be ________? | stricter |
| If you don't receive what is ordered what should you do? | Send it back |
| What order should you use when verifying and ordering lenses? | Base Curve; Power; Diameter; OZ, CT |
| ANSI standards for Base Curve? | +(-)0.05 |
| ANSI standards for power 0.00 to 5.00 D | +(-)0.12 |
| ANSI standards for power 5.12 to 10.00 D | +(-)0.18 |
| ANSI standards for power 10.12 to 15.00 D | +(-)0.25 |
| ANSI standards for power 15.12 to 20.00 D | +(-)0.37 |
| ANSI standards for power over 20.00 D | +(-)0.50 |
| ANSI standards for Diameter | +(-)0.05 |
| ANSI standards for Posterior Optical Zone | +(-)0.10 |
| ANSI standards for Center Thickness | +(-)0.02 |
Created by:
griffiskr
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