UV absorption is different than a tint
Tint refers to merely the the color of the lens
UV protection is necessary b/c much of the light in the UV and IR regions of the spectrum that strikes the eye will reach the retina
Transmission is the mount of light that passes through a lens
Glass, sand, snow, pavement and metal are all good polarizers of light by reflection
Photochromic lenses can also be referred to as variable tint lenses
A photochromic lens will change its transmission when exposed to light
When glass photochromic lenses are activated by UV the silver and halogen combine to form silver halide
Response and recovery time for glass photochromic lenses is dependent on the glass material
A
B
C
All of the above
A and C
A
B
C
A and C
B and D
A
B
C
A and B
B and C
Are a number of thin optical coatings applied to one side of the lens to reduce reflections
Result in reduced reflections that increase light transmission through the lens
Eliminate the specularly reflected light and improves visual acuity
Reflect light that will be perpendicular to the plane of incident light
Correct increased retinal contrast
Chemically tempered glass are more impact resistant than CR-39 against large slow moving objects such as a softball but CR-39 is more impact resistant against small high velocity objects
Benefits of Trivex include easier tinting, and less chromatic aberration. Trivex is also the lens of choice for drill mounted lenses.
By law, all eyeglass and sunglass lenses must be impact resistant EXCEPT when such a lens will not otherwise fulfill the patient’s visual requirements
Anyone edging, coating or tinting a lens is considered a “manufacturer” of the lens and can be held liable for the impact resistance of that lens
Plastic lenses must be heat treated and treated with a chemical bath in order to become impact resistant.
True
False
Chemical tempering can only be done on Crown or high index glass
Chemical tempering creates more impact resistance than thermal tempering
Air/Thermal tempering can be done on all materials
During thermal/air tempering the lenses are heated to 650C and then rapidly cooled, producing surface compression and internal tension
Chemical tempering takes longer than Air/thermal tempering and the end product is not as impact resistant as the end product of chemical tempering
True
False
A
B
C
D
All of the above
B and D
A
B
C
D
A and D
A, C and D
True
False
AR coatings and scratch resistance coatings will increase impact resistance
AR coatings and and scratch resistance coatings absorb the impact energy and increase resistance in plastic
Without a coating, plastic will not flex on impact
Glass is weakend more my scratching than CR-39
Monocular individuals
Athletes
Children
Low myopes
Machine operators and plumbers
The spectacle frame test evaluates the strength of the temples and side shields. It requires that the frame or lenses much not come into contact with the eye
The purpose of the high velosity impact test is to proive that a frame can withstand the impact of small objects traveling at high speeds.
In order to pass the high velocity impact test no frame or lens breakages may result, and the lens can't come out of the frame
The high mass impact test is done the same way as the the high velocity impact test
"B" dimension
DBL
Manufacturer's identifying trademarks
"Z87" for 3.0mm thickness lenses - basic impact lenses
"A" dimension
There are 2 classes of multifocal lenses: segmented multifocals and progressive addition lenses (PALs)
As the patient's add power increases the near working distance increases
If you prescribe according the patient's age you would start off my giving a 40 year old b/t 1.00-1.75 Add
According to Dr. Y by 60's and older you would be giving your patient 3.00D add/Absolute add
A
B
C
D
Image jump at the seg top
Image jump at the reading level
Overall lens thickness
Chromatic aberration
Total displacement at the reading level
If the prismatic power of the distance portion differes from the prismatic effect of the seg, the images "jumps"
The image jump decreases the farther the segment OC is away from the top of the segment line
Image jump results from the vertical prismatic effect at the line b/t the carrier lens and the segment
The differential displacement of light at the top of a seg results in an apparent scotoma
Image displacement through a seg occursif the reading level is NOT coincident with the seg OC
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Here's an interesting quiz for you.