Help
Options
Didn't know it?
click below
click below
Knew it?
click below
click below
Don't Know
Remaining cards (0)
Know
retry
shuffle
restart
0:00
Embed Code - If you would like this activity on your web page, copy the script below and paste it into your web page.
Normal Size Small Size show me how
Normal Size Small Size show me how
Contact Lens
CL- 201
| Question | Answer |
|---|---|
| ___ accomodate and converge more with their contacts on? Why | Myopes. The simulus for accomodation is greater. Their eyes will tire more easily and may develop near pt problems. |
| ____ accomodate and converge less with contacts on? Why | Hyperopes, less stimulus for acc |
| The diameter of a lens is determined by | Corneal curvature (steeper=smaller), pupil size (larger pupil larger diameter), palp aperture size, philosophy of lens design (may always come in a certain diameter) |
| ___ is the optic zone/base curve | central posterior curve of the lens (note in SCL it is the frong curve) |
| Optic zone is determined by | Size of the lens (bigger lens needs bigger OZ), Pupil size (needs to be at least size of the pupil) Philosophy (if want bigger OZ may need to inc the dimater) |
| Algined, Steep and flatter all describe | The base curve relative to the corneal curve, compares the flat K of cornea to the BC of the lens. |
| When measuring the BVP of a lens put it on the lensometer ___ side down. BVP is ___ in ___ than FVP | concave side down. BVP is higher in plus power than FVP |
| If the center of gravity is more toward the front of the cornea what occurs? In a minus lens where is the center of gravity? Plus? | If more front, the lens will slide down more. Minus lenses have a further back C of G thus stay on the eye better. Plus lenses act like a watermelon seed with C of G more toward the front. Also note the steeper the lens the further back the CofG moves |
| Why does a minus lens stay on the eye well. | 1. Further back Center of gravity, 2. Good lid grab |
| 3 factors determine the final power of Cl | Pxs rx, effectivity, tear lens |
| When correcting for tear lens and you see steep or flat flourescein patterns what to do? | Steep Add Minus (SAM) Flat Add Plus (FAP) ex minus tear lens want to add plus |
| Center thickness is greater in | plus lenses |
| Peripheral curve system is described by what two parameters | radius and width |
| Edge thickness should be around? why? | .08-.12 Thin edge= comfort otherwise lead to 3 and 9 oclock staining. Can also taper the end by polishing for comfort, or roll it. |
| vertical distance from the lens edge to the extension of the base curve | Axial edge lift |
| Extension of the lens edge perpendicular to the extension of the base curve | Radial edge lift (80% of the AEL) |
| What is edge clearance | space btwn the peripheral lens dege to the cornea measure along the line parallel to the lens optic axis. glows green. PMMA very thick. How much lift the lens has against the peripheral cornea. |
| If edge lift is too great what can occur? what would you do? | discomfort, frothing (bubbles), staining (3 and 9), ejection, excessive movement. Steepen the peripheral curve radius or narrow the periperal curve width. |
| silicone is good for ___ but bad for ___ | permeability to O2, bad for wettability and increases debris buildup |
| Color in RGPs blocks ___ % of light | 2 |
| What new material is good for permeability and wettability | Fluoro Silicone Acrylates (FSAs) |
| Empirical Fitting involves. Major problem? | No lenses on eyes more based on computers K's rx, Major problem is you can't anticipate lid action. Good for weird cases to order initial diagnostic lens. |
| Diagnostic Fitting involves? | Diagnostic lenses, more trials, more time, more costly, More ACCURATE. Store lenses dry. Usually based on corneal K's and palp aperature |
| What are the 3 basic RGP lens designs | 1. Interpalpebral. 2. Basic Tri-Curve 3. Korb or Lid Attachment |
| Interpalpebral lenses | fit btwn the lids. Not used as much, use with a px with large apertures with lid problems. Ultra thins helps comfort. Smaller diamters (8-8.6), fit slightly steep, Bad for big pupils or small eyes. |
| Basic Tri-curve tetra curve (bennett design) | Everyday RGPs, fits under superior lid. Not lid attached. 9.2-9.4mm, base curve depends on corneal toricity |
| Korb or Lid attachement | Anterior front surface periphery of lens attaches to the lid and moves with it. May looks like a tight fit, look for movement via pulling down lower lid. Note lid involved eyes that fit steep ride high |
| Lens adherence = | V=dh or (optic zone diameter * radius of base curve) |
| The SAG increases if you change what | Inc the diamter and keep BC constant. |
| This tells you how the cornea or CL flattens as you go out to the periphery. Avg cornea = | Eccentricity value = .55 |
| An eccentricity value of .6 means | that the cornea flattens in the periphery faster than the avg cornea. Radius normally inc in perphiry flattening base curve. |
| If your cornea has a ecc value that flattens faster you have to watch the | OZ. If inc OZ the lens may fit a little steep on a flat cornea in the periphery. |
| The OZ has an important relationship btwn | the front of the cornea and the back of the lens at the OZ |
| Common diamter/OZ combo | 9.2/7.8 |
| To maintain a constant sag... If the BC is flattened by .25D, steep by .25D? | Need to inc OZ by .5mm, Dec OZ by .5mm |
| In a tri curve lens, the BC is ___ the SCR is ___ the PCR is ___ | say 7.5, the SCR is 1 to 1.5 flatter than BC and PCR is 1.5-2.0 flatter than SCR |
| Overall diameter for Tricurve = | OZ + 2 (SCW) + 2 (PCW) |
| Tetra curve lens is SCR = TCR= PCR = | SCR= BC +.8mm, TCR= SCR +1.0mm PCR= TCR +1.4mm |
| Tetra curve widths | SCW = .3, TCW = .2 PCW =.2 |
| Overal diameter for tetra curve = | OZ + 2 (SCW) + 2(TCW) + 2 (PCW) |
| This is used to smooth out the junctures between the BC and SCR. Tool size | Blends. 8.00mm can be light, med, or heavy 3 blend types J1, J2, J3 |
Created by:
Kswingin