Environmental Applications Flashcards
consists of two polarized filters, one on the top and one on the bottom of the instrument with their absorption are perpendicular, i.e., cross-polarized
Polariscope (colmascope)
Two tests used to verify impact resistance?
- high mass impact
- high velocity impact
Tempering or toughening of glass lenses
Heat treatment
What are 2 things required for glass lenses hardening?
Heat treatment and chemical treatment
chemical tempering, the process of increasing the impact resistance of glass lenses by immersing them in a bath of molten potassium nitrate
Chemical treatment
What treatment has a greater impact resistance, chemical or heat?
Chemical
What treatment can be applied to objects of complex shape, chemical or heat?
Chemical
What are 2 pros regarding heat treatment?
- its quick
- equipment is inexpensive
A normal lenses placed between the filters of a polariscope appears ___
Uniformly dark
What type of lens demonstrates stress patterns (Maltese Cross)?
Tempered lens
When giving lenses what do you need to put beside a lens with variable tint?
V
When giving lenses what do you need to put beside a lens with special purpose?
S
For a impacted rated plano, how is it marked?
Z87+
For a impact rated rx, what would you mark?
Z87-2+
Glasses aimed at those with color deficiency or those working with veins and blood
Oxy-ISO glasses
What 2 lenses are used for color deficiency?
- enchroma
- oxy-ISO glasses
These glasses enhances the O2 signal from
hemoglobin under the skin -> -> -> amplifies the perception of veins under the skin
Oxy-ISO glasses
Two frames that passed NASA’s rigorous testing and
will be worn by astronauts. And supplies the interchangeable magnetic rx lenses. It takes off weight and keeps you from not bringing multiple glasses.
Switch vision
Movie theaters use these
Close caption glasses
Glasses that record you
Snap spectacles
Bone conduction tech so you don’t need earphones, touch interface to control music and calls
Conduction technology
Liquid lenses that change shape according to the distance of objects
Smart glasses
Smart glasses are made from what?
Glycerin
How many long does it take smart glasses to adjust?
14 milliseconds
How do anti-reflection coating work?
They produce two reflection which interfere destructively with each other
The coating applied to the lens surface is ___of the wavelength of light thick
1/4
The reflected path from the back of the AR coating will be ___ longer
1/2 wavelength
Light reflected from the back of the AR coating is ___ degrees out of phase from light reflected from the front
180
The amplitude of the light reflected at each surface of the AR coating is equal what will happen?
They will cancel each other out
Where the amplitude of light reflected from
each surface of an AR coating is equal and, if 180 degrees out of phase, will cancel each other out. For this to occur, the refractive index of the coating must be equal to the square root of the refractive index of the lens material”
Amplitude condition of AR coating
Why do you need multiple layers of different indices?
Because they are wavelength specific
Original glass photochromic manufacturers
Corning photochromic
The reactions of the glass photochromic lens are mediated by?
Atoms of silver
Designed to reduce glare while driving at night
DriveSafe Lenses
Lenses that changes in the size of the driver’s pupils is taken into account while driving
DriveSafe Lenses with luminance design technology
What 3 things do DriveSafe Lenses do?
- produce better vision in low light conditions for safer and more comfortable driving
- reduced glare at night from oncoming cars or street lights
- accurate view of the road dashboard and mirrors
Progressive lenses that are used for people who want small frames
Short-fit progressives
You would use these if the B measurements are less than 30
Short-fit progressives
lens designed to emphasize intermediate and near vision. Used for computer use, office-related tasks
Occupational PAL
A very wide intermediate, near, with low level of unwanted astigmatism in the periphery
Occupational progressives
For people who work inconfined spaces that need to
see up close, above and below them, without moving their heads
Double segment flat top bifocals
Lenses where the bottom is near, top is near, and remainder is distance
Double segment flat top bifocals
Lenses where the bottom is near, the top is intermediate or near, and the remainder is distance
DD Occupational lens (tri)
lens placed in a frame which looks like the lens for the opposite eye to balance appearance andweight
Balance lens
a lens style where both the front and back surfaces are plus
Bi-convex
A lens style where both front and back surfaces are minus
Bi-concave
Indicates the designated eye is not sighted, so the same number should be entered for both eyes; similar in thickness and style, but no specific Rx power
Balance lenses
distance only correction in one eye, near vision
correction in the other eye
Monovision
With monovision, the eye that sees distance well will be blurred ___ and the eye that sees near will be blurred at ____
Sees distance: blurred up close
Sees near: blurred at distance
What eye is usually used for distance vision
Dominant eye
What are 4 limitations of monovision
- Distant objects appear slightly blurred
- Lack of intermediate vision
- Doesn’t provide adequate near vision for sustained reading
- Although the two eyes still work together, binocular vision is compromised, causing a decrease in depth perception
Lenses generally used to correct extreme hyperopia.
Lenticular lenses
In order to limit the thickness and weight that a
high-powered lens would normally
require, what happens? (In a lenticular lens)
all of the power of the lens is concentrated in a small area in the center
A minus lenticular lens. Used for high minus corrections
Myodisc
What are some ways you can reduce thickness regarding frame shape and size
- smaller lens opening
- less wide, less tall, rounder the better
For a plus rx what do you want to do to reduce thickness (regarding shape and size?
Smaller a good idea but less impact than minus rx
To reduce thickness what type of frame do you want to avoid?
Rimless and semi-rimless
To reduce thickness what type of frame do you want to hide the thickness?
Full plastic frame
What are the pros of polishing lenses?
Exposed edges are polished to enhance finished invisible look of lens
What are the cons of polishing lens?
Seeing rainbows
What are the techniques used to reduce thickness?
- round shape
- smaller lens opening
- full plastic frames
- lens edging choices that hide thickness
- high index lenses
- roll and polish
- centering the OC over GC
- edge painting (edge matched to frame color)
flatter base curves result in ___ lenses, but steeper
base curves have less ___
Thinner lenses and less distortion
How long should it take patients to adapt to small base curves?
Within a week
Do you want to keep base curve similar/same between the two eyes and similar/same as previous base curves?
Yes
What are some complaints people have when they have polycarbonate lenses?
Complaints about VA and chromatic aberrations
Polycarbonate has a ___ abbe value
Low
