UNIT 1: The Dispenser's Role in Solving Problems Flashcards
What are the different types of problems?
- Comfort
- Repair
- Vision
- Psychological/Emotional
Pads digging into sides of nose is what type of problem?
Comfort
What causes pads to dig into the sides of nose?
- Pads too tight
- Temple tension too great
- Pads too small for weight of glasses
- Tender skin
What are solutions for pads digging into the sides of the nose?
- Widen distance between pads
- Reduce temple tension
- Use larger pads
- Toughen skin with witch hazel
Pads digging into nose unevenly is what type of problem?
Comfort
What causes pads to dig into the nose unevenly?
- Pads do not fit flatly against the nose
- Temple angle is greater on one side
What are some solutions for pads digging into the nose unevenly?
- Correct frontal and splay angel
- Correct temple spread
Temples hurting behind ears is what type of problem?
Comfort
What causes temples to hurt behind the ears?
- Tension too great
- Uneven pressure
- Area of contact between temple and ear too small
- Temples too short
What are solutions for temples hurting behind the ears?
- Loosen temple tension
- Bend temples to conform to the shape of the ears and skull.
- Fit longer temples
Spectacles sliding down the nose is what type of problem?
Comfort
What causes spectacle to slide down the nose?
- Distance between pads too great
- Temple tension too weak or temples too long
What are solutions for spectacles sliding down the nose?
- Bring pads closer together
- Increase tension or replace with shorter
temples.
Eyewire touching cheeks is what type of problem?
Comfort
What causes eye wires to touch cheeks?
- Too great distance between pads
- Too great a pantoscopic tilt
- Lenses too large in vertical dimension
What are some solutions for eye wires touching the cheeks?
- Bring pads closer together
- Reduce pantoscopic tilt
- Refit with smaller eyewire.
Lenses touching brows is what type of problem?
Comfort
What causes lenses to touch the brows?
- Lens bevel position
- Resting point on nose is too high
- Too much retroscopic tilt
What are solutions for lenses touching the brows?
- Lengthen pad arms
- Lower spectacles by raising pad arms
- Reduce retroscopic tilt
Lashes touching the lenses is what type of problem?
Comfort
What causes lashes to touch the lenses?
- Distance between pads is too great
- Temple tension too great or temples too short
- Pad arms too short
What are solutions for lashes touching the lenses?
- Bring pads closer together
- Reduce tension
- Replace with longer temples
- Lengthen pad arms
- Use steep base curve
When would you need to repair frames?
- Defective
- Normal wear
- Abuse
When would you need to repair lenses?
- Defective
- Abuse
When comparing previous pairs of glasses, observe
- Large change in RX
- Optical center placement
- Change in base curve
- Change in lens size and material
What is the Tscherning Ellipse?
- A graphical representation of the front surface power as a function of the total lens power in best form lenses.
- There are two possible solutions, those that are least curved and those that are most curved.
What are aspherical lenses?
- non spherical surface that gradually changes
in curvature from the center of the lens
toward the edge. - Delivers the peripheral clarity of a Best - Form
lens with a flatter profile. - With high index, up to 25% thinner and 30%
lighter.
What are the 3 main uses of aspherical curves?
1) Optical aberration control = improved off
center optics for RX’s > +7.00 or -23.00D than
spherical base curve.
2) Cosmetic = Allows the use of flatter base
curves while maintaining good optics.
3) Power changes = used for progressive
addition lenses.
Check fit of new glasses list
- Pantoscopic tilt
- Vertical optical center placement
- Parabolic curve
- Vertex distance
- Segment height, equality
- Frame level
What is used to measure vertex distance?
Distometer or mm ruler
Vertex distance formula
(DxD) / 1000
Anisometropia
Considered to exist when the spherical equivalent refraction of the two eyes differs by 1.00D or more.
Aniseikonia
The relative differences in sizes and/or shapes of the ocular images of the two eyes.
What are causes of vertical imbalance?
- Refractive error
- Refractive surgery
- Cataract surgery
- Injuries
- Presbyopia
- Occupational viewing positions
What are methods of correcting vertical imbalance?
- Contact lenses
- Two pair of glasses
- Adjusting the MRP or seg height
- Fresnel Press on prism
- Dissimilar segs
- Compensated R segs
- Slab off
What is prentice’s rule?
The prismatic effect of a lens on rays of light that pass through it at points other that its optical center is equal to the product of the the dioptric power of the lens and the distance in cm for the optical center to the point of passage.
What is prentice’s formula?
Prism = P x dcm
P= Lens power in diopters
dcm = distance in cm
FILL IN THE BLANK
For horizontal prism problems always find the total power in the _____________ meridian.
Horizontal
FILL IN THE BLANK
For vertical prism problems always find the total power in the _____________ meridian.
Vertical
of degrees away from cyl = % cyl power
CHART
square the sine of the angle between the axis and the 90th meridian.
Vertical prism ( Imbalance)
- Determine the power in the vertical meridian
- Determine the power difference between each
lens. - Determine prism at the reading level (usually
10mm) ^ = P x dcm - If the imbalance is greater than 1.50 ^ consider
slab off, base up atleast plus or highest minus.
Reverse for reverse slab.
When evaluating the need for correction look at
- Age
- Amount of imbalance
- Cause of imbalance - onset
- Reading position
What are some solutions for vision problems?
- Changing the lens material
- Add, change, or remove tints/coatings
- Return to the refractionist
Psychological/Emotional problems include
- Anger
- Appearance
- Cognitive Dissonance
