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Dispensing Test 3
| Question | Answer |
|---|---|
| Who invented the Snellen Chart? | Hermann Snellen |
| What year was the Snellen Chart created, and during what war? | 1862, Civil War |
| Who did Snellen use to determine what was normal vision? | sharp shooters |
| Sharp shooter could discern a feature that subtended an angle of ___ to their eye? | 1' (minute) |
| How many minutes are in one angle? | 60 |
| How tall are the letters on the 20/20 line of the Snellen chart? | 8.87 |
| A whole letter subtends an angle ___ from the eye, but able to discern features at ___? | 5' ; 1' |
| The first number in the phrase "20/20" symbolizes what? | distance at which the test is done |
| The second number in the phrase "20/20" symbolizes what? | distance at which a person with normal vision could read the letters |
| What is a person's visual acuity if they see the big E on the Snellen chart? | 20/200 |
| How can you determine the size of the letters of any line on the chart? | divide the denominator by the numerator, and multiply by 8.87 |
| What are some things that effect visual acuity? | Contrast; lighting (illumination); pupil size |
| If a pinhole doesn't correct or help vision problem is not refractive, it is...? | neurological |
| Which would help visual acuity a larger pupil size or smaller? | smaller |
| What is presbyopia? | Loss of sufficient accommodation at near; crystalline lens can't get as plus anymore |
| How much of total accommodation can be used comfortable for a long amount of time? | Half |
| What are symptoms of presbyopia? | blur, headaches, double vision |
| How is presbyopia corrected? | More plus power, convex lens |
| What are some options for prebyopes? | Bifocals, trifocals, single vision readers; two pairs of glasses; monocle; contacts monovision; slide glasses down nose; half-eyes |
| What is used to check near VA? | Reduced Snellen Chart; Jaeger system |
| What are the differences in the Snellen chart and Jaeger? | The distance at which the charts are read, and the Jaeger system is slightly larger. Snellen chart is more accurate |
| What distance is the reduced Snellen read at? | 16 inches |
| What distance is the Jaegar system read at? | 14 inches |
| What is early presbyopia? | When the near point of the distance prescription is closer than the far point of the add; there is an area that can be seen through distance and add |
| What is middle presbyopia? | When the near point of the distance and the far point of the add are at the same place. |
| What is advanced presbyopia? | When a gap exists between the near point of the distance and the far point of the add; use trifocal to fill in gap. Used when add power gets to +2.00 |
| What are some fitting problems with first time bifocal wearers? | restricted field of view; upsets depth perception (things look bigger and closer); nuisance to wear; cylinder changes shapes of objects; reflections; changes in reading habits; bifocal lines bisect field of view; curbs and stairs |
| How well a patient adapts to wearing bifocals depends on.... | how the glasses fit into lifestyle; your measurements; your adjustments; and how well you prepare them |
| Where do we measure for a lined bifocal? | lower lash line |
| Where do we measure for a trifocal? | bottom of pupil |
| Where do we measure for a child's bifocal? | center of pupil |
| Where do we measure for a progressive lens? | center of pupil |
| What type of frames are good for first time bifocal wearers? | frames with adjustable nosepads; gives some leeway to adjust segment |
| If you have a previous bifocal wearer is it good to set their bifocal where they've always had it? | Yes, it may bother them if you change it. But ask, the patient may want you to change it. |
| How do you want to set a child's bifocal? | High and wide so they don't look around it; bisect the pupil |
| What is accommodation? | when your eye accommodates for different distances. |
| The near point _______ as you age. | recedes |
| What is the formula for accommodation power? | (5-Age/4)=Accommodative power |
| What is the difference in myopes and hyperopes when fitting for bifocals? | Myopes can get along without glasses when needing to read up close; can get away with smaller/lower segments |
| When specifying center thickness, what is the minimum for dress eyewear? | 2 mm |
| When specifying center thickness, what is the minimum for safety eyewear? | 3 mm |
| When is it important to pay attention to center thickness on a bifocal? | When using a fused segment |
| Most bifocals are set too ___? Why? | low; opticians are afraid to set bifocal correctly, afraid the patient will see the line |
| If a patient has a stooped posture, their bifocal needs to be set...? | higher |
| If a patient has a very erect posture, we need to set their bifocal...? | lower |
| If a patient is really short their bifocal should be set...? | higher |
| If a patient is really tall their bifocal should be set ...? | lower |
| What methods are used to measure seg height? | mm ruler (PD stick); seg measures (not used anymore); transparent tape; marker; white marker; electronic |
| Should seg heights be set equally? | Yes, it's best for optics, but not good cosmetically; progressive is best |
| Closer VD = _____ field of view | wider |
| Farther VD = _______ field of view | smaller (narrower) |
| Segs are less noticeable when what is used? | AR coating |
| If a patient does alot of near work, we want their segment to be...? | wider and set higher than normal |
| If patient doesn't use their near vision as much their seg can be...? | narrower and can be set lower |
| With a high power distance Rx how do we want the seg set? | Get bifocal as close as possible; set bifocal higher |
| How does panto affect seg height? | Increase the panto, it lowers the apparent seg height |
Created by:
griffiskr
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