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Dispensing Test 3

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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