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LDO Review

QuestionAnswer
What is the refractive index of CR-39? 1.49
What is the refractive index of Crown Glass? 1.523
What is the refractive index of Trivex? 1.53
What is the refractive index of Polycarbonate? 1.58
Higher the ABBE number, the ________ the material is. Heavier
What is the refractive index's of High Index? 1.60, 1.67, 1.71, and 1.74
What is the ABBE value for crown glass? 59
What is the ABBE value of CR-39? 58
What is the ABBE value of polycarbonate? 30; very poor optical quality
What is the ABBE value of Trivex? 43
What is ANSI Z87.1 standards for? occupational or safety glasses
What is minimum thickness for safety eye wear? 3 mm; plus lenses over 3.00 D can have a minimum thickness of 2.5 mm
The point on the lens where a ray of light will pass through without any deviation? Optical Center
The point on the lens that equals the amount of prism prescribed, if any? Major Reference Point
The point equal distance from the lens edge? Geometric Center
The point at which a lens is edged? Mechanical Center
An optical unit of measure that describes the deviation of light after it passes through a lens? Diopter
The distance from the back vertex of a lens to the focal point? Focal length
What lens has identical curvature in all meridians? Spherical lens
What lens has unequal curvature in all meridians? Cylindrical lens
In this condition the globe of the eye is too short? Hyperopia
In this condition the globe of the eye is too long? Myopia
This condition causes a Virtual Image on the retina? Myopia
This condition causes a Real Image on the retina? Hyperopia
This lens type has against motion? Plus lenses
This lens type has with motion? Minus lenses
This lens type has scissor motion? Cylinder lenses
What technique is used to show the Rx of an ophthalmic lens in its primary meridians? Optical cross
What is the curve from which all other curves are determined? Base curve
If you flatten the base curve the image gets what? Smaller
If you steepen the curve the image gets what? Bigger
The lens clock is calibrated to what? 1.53
When light enters a prism it is deviated towards the what? The base
Chromatic aberration is measured by what? Abbe Value
True or False. The higher the abbe value the lower the amount of chromatic aberration. True
The bending of light as it passes obliquely from one medium to another is what? Refraction
What is the speed of light in air? 186,000 mps
What indicates how much the material will refract or bend light as it enter the material from air? Refractive index
What material has a abbe value of 58? CR-39
What material has a abbe value of 59? Crown glass
What material has a abbe value of 43? Trivex
What is the abbe value of polycarbonate? 30
If a plus lens is moved away from the face the Rx gets what? Stronger
If a plus lens is moved closer to the face the Rx gets what? Weaker
If a minus lens is moved closer to the face the Rx gets what? Stronger
If a minus lens is moved away from the face the Rx gets what? Weaker
Determining the portion of cylinder power away from the axis is called what? Oblique Cylinder Power
What percent of cyl power is there 90 degrees away from the axis? 100%
How much cyl power is there on the axis? none
What is the most common way to correct for vertical imbalance? Slab off prism
What is used to verify slab off? Lens Clock
What is the formula for prentice rule? Prism=Diopters x Distance mm/ 10
Where are trifocals measured from? the bottom of the pupil
Where are bifocals measured from? The lower lid
Where are progressives measured from? center pupil
Overexposure to UV light can cause what? Cataracts and ARMD
What type of UV is the most harmful to the eye? UV-B
What type of UV is the least harmful to the eye? UV-A
When an eye is suppressed for too long it results in what? Amblyopia
A FIXED turning of the eye is what? tropia
A TENDENCY for the eye to turn is what? Phoria
OD: +1.00 OS: -1.00. What would this Rx be an example of? Antimetropia
When one eye is markedly stronger than the other? Anisometropia
A condition where the patient sees different image sizes in each eye? Aniseikonia
What are the 5 layers of the cornea in order? 1.Epithelium 2.Bowman's Membrane 3.Stroma 4.Descemet's membrane 5.Endothelium
A thick transparent substance that is mainly water and 2/3 of the eyes volume is what? The Vitreous
One meridian is plano and the other is myopic, Ex PL-2.00x180. Simple myopic astigmatism
One meridian is plano and the other is hyperopic, Ex PL+2.00x180 Simple hyperopic astigmatism
Both meridians are myopic, Ex -2.00-2.00x180 Compound myopic astigmatism
Both meridians are hyperopic, Ex +2.00+2.00x180 Compund hyperopic astigmatism
One meridian is myopic and other is hyperopic, Ex -1.00+2.00x180. Mixed astigmatism
Instrument used to neutralize a lens? Lensometer
How thick is the cornea? .5mm
What regulates the amount of light entering the eye? Iris
What must be adjusted prior to using the lensometer? The eye piece
What type of bifocal can be manufactured as a fused segment? flat-top
according to ANSI standards, when is it important to consider vertex changes? When the power exceeds +/- 7.00D
What is a lens shape called that has one convex surface and one concave surface? a meniscus lens
Where is the optical center located on a round bifocal? In the geometric center
What is the most common intermediate power for trifocal lenses? 50% of the add power
What type of bifocal segment has the least amount of image jump? Flat-top
light rays that originate at a distance point can be described as what? Parallel
What is the focal length of a 2.50D lens? 40cm
What is double vision called? Diplopia
What type of coating allows more light transmission through the lens? Antireflective coating
How do you find total lens power? Adding the front surface power and the back surface power together. F1+F2=total lens power
What is the formula for focal length? FL=1meter/Diopters or Diopters=1meter/FL
How many centimeters are in a meter? 100cm
If a lens has a front surface power of +6.00D and a back surface power of -7.00D. What is the focal length 100cm
Which of the following lenses have NO power in the 90 degree meridian, +1.25-1.25x090 or +1.50-1.50x180? +1.50-1.50x180
if a lens has a front surface power of +6.50D and a back surface power of -8.00D. What is the total power of the lens? -1.50
A +10.00D lens is moved 5mm closer to the eye. What new power will be needed to compensate this change in vertex distance? +10.50D
A patient has an Rx of -10.00D and was refracted at 12mm. If he is fit at 7mm what is the effective power of the lens?? -10.50D
Where is the vertex distance measured from? from the back surface of the lens to the front surface of the cornea
If your patient is blind in one eye, what is the best lens material to use in there glasses? Polycarbonate
A minus lens moved up created what type of prism? Base down prism
What type of zyl frame allows the frame to rest entirely on the nose? saddle
How many layers does the retina have? 10
What is responsible for peripheral and night vision? Rods
What is responsible fore central and color vision? Cones
What is the outer most layer of the eye responsible for protection? Sclera
How many muscles are attached to the eye? 6
What muscle moves the eye upward? Superior Rectus
What muscle moves the eye downward? Inferior Rectus
What muscle moves the eye nasally? Medial Rectus
What muscle moves the eye temporally? Lateral Rectus
What muscle rotates the eye inward and down? Superior Oblique
What muscle rotates the eye outward and up? Inferior Oblique
What does the Superior Rectus muscle do? Moves the eye upward
What does the Inferior Rectus muscle do? Moves the eye downward
What does the Medial Rectus muscle do? Moves the eye nasally
What does the Lateral Rectus muscle do? Moves the eye temporally
What does the Superior Oblique muscle do? Rotates the eye inward and down
What does the Inferior Oblique muscle do? Rotates the eye outward and up
What is the refractive index of the crystalline lens? 1.427
What is the clouding of the crystalline lens called? Cataracts
What is known as the silent thief of sight? Glaucoma
What are the colors of the electromagnetic spectrum? ROYGBIV
What are wavelengths measured in? Nanometers
How many millimeters are in a meter? 1,000mm
In the electromagnetic spectrum what is considered visible light? 380-760nm
What colors is the eye most efficient at detecting? yellow and green(535nm)
What type of lens is Bi-Concave? Minus lens
What type of lens is Bi-Convex? Plus lens
The prescription -3.25+4.25x180, can also be written as? +1.00-4.25x090
In safety glasses how thick do the lenses have to be? 3mm thick
What is the condition in which the crystalline lens is missing from the eye? Aphakia
What is the condition in which the brain suppresses one eye due to disuse? Amblyopia
An object viewed through a prism appears towards the what? The apex
When a lens is placed on a neoprene gasket and a 5/8" steel ball weighing .56oz is dropped from 50 inches is called what? The drop ball test
What are the two ways to increase impact resistance of a lens? heat treating and chemical tempering
How long does the FDA require records to be kept? 3 years
What is it called when a frame front is parallel to the patients face? orthoscopic tilt
What is it called when the lower eye wire is closer to the patients face then the top of the frame? pantoscopic tilt
What is it called when the top of the frame is closer to the patients face then the bottom eyewire? retroscopic tilt
The horizontal distance between the furthest temporal and nasal edges of the lens is known as what? The A measurement or the eye size
The vertical distance between the furthest top and bottom edges of the lens is know as what? The B measurement
The shortest distance between the nasal edges of each lens is known as what? The DBL
Twice the distance from the geometric center of the lens furthest edge of the lens is known as what? The ED
The running distance between the middle of the center barrel screw hole and the end of the temple is what measurement? Temple length
What is the end piece on a frame? the point where the temple attaches to the chassis
What is the basic metal nickel based material called? Monel
What are the benefits of a titanium frame? light weight, durable, hypo-allergenic, and corrosion resistent
What are the benefits of flexon frames? light weight, hypo-allergenic, and corrosion resistant
A steel gray metal, that is a lower cost alternative to titanium and is light weight, strong and flexible? Beryllium
What is the frame material that is used in high end eye wear and is light weight and corrosion resistant? Aluminum
What material is commonly used for sports and performance frames? Nylon
What frame material is nylon-based, hypo-allergenic, and light weight? Cellulose Acetate
What frame material is a cold insert and shrinks or stretches when heated? Polyamide
What frame material has to be heated to 83 degrees celsius to be adjusted? Optyl
What frame material is rigid, strong, light weight and very popular with designers? carbon fiber
A lens has a front surface power of +2.00D and a back surface power of -8.25D. What is the total or corrective power of the lens? -6.25D
Using the prescription -1.00-1.50x90, what is the power of the lens at the 180th meridian? -2.50D
What is the spherical equivalence of the lens +1.00+2.50x090? +2.25D
A lens having one concave and one convex surface is called what? meniscus lens
What lens treatment best reduces glare from water and road surfaces? Polarized
Slab off is used to compensate for differences in induced prism between the eyes caused by what? Anisometropia
Internal lens stress can be detected using what? a polariscope
What is used to measure vertex distance? Distometer
A lensometer reticle is divided in quadrants to measure what? the direction of prism
Who is the private agency that sets commercial and industry standards? ANSI
which lenses are not exempt from drop ball testing? Aspheric
According to ANSI standards, a lens with 0.50D of cyl must have an axis within how many degrees? 7 degrees
What is the corneas refractive index? 1.37
The rim around the lenses is known as what? the eyewire
the area of the frame front that rests on the nose? the bridge
The outer areas of the frame front where the temples attach is called what? endpieces
What holds the temples to the frame front? Hinges
The place on the temple where it first bends down to go over the ear is called what? The bend
What temple bends down behind the ear and follows the contour of the skull? Skull temple
What temple is practically straight and holds the glasses on by pressure against the head? Library temple
What temple can be bent down around the ear and also straight back on the head? Convertible temple
What temple curves around the ear, following the crotch of the ear where the ear and the head meet and extend to the level of the earlobe? Riding bow temple
What temple is the same shape as the riding bow but is of metal construction? Comfort Cable temple
What type of frame only holds the lenses in place at their nasal edge? Numont
Before the lens has been edged it is called what? A lens blank
What is the lens blank called when it has the correct powers called for in the prescription and only needs to be edged? Finished
What is the lens blank called that has only one side finished and the other still needs to be ground and polished to the correct prescription? semi-finished
Where must the center thickness of a lens be measure from? the OC
According to ANSI standards what is the axis tolerance of a 0.25D cyl power lens? 14 degrees
According to ANSI standards what is the axis tolerance of a 0.50D cyl power lens ? 7 degrees
According to ANSI standards what is the axis tolerance of a 0.75D cyl power lens? 5 degrees
According to ANSI standards what is the axis tolerance of a 1.00D, 1.25D, and 1.50D cyl power lens? 3 degrees
According to ANSI standards what is the axis tolerance of a >or = to 1.75D cyl power? 2 degrees
In a sphere lens what is the error tolerance according to ANSI standards? 0.12D
According to ANSI standards, a cyl power of 2.00D has a power tolerance of what? 0.13D
Accordign to ANSI standards, cylinder powers between 2.25D and 4.50D has a power tolerance of what? 0.15D
How do you find spherical equivalence? take half the cylinder and add it to the sphere
sagittal depth is used for what? determining lens thickness
Moving the optical center of a plus lens downward will produce what type of prism? base down
Moving the optical center of a minus lens down will produce what type of prism? Base up
A prism made from thin flexible material and consists of small rows of equal powered prisms resulting in the same effect of a conventional prism is called what? Fresnel prism
The ABBE value is commonly used to identify what? Chromatic abberation
What type of lens design does not have a spherical lens surface? Aspheric
When is it necessary to use an aspheric lens? With a high plus or minus lens
True or false, you can use an aspheric lens when the prescription has cylinder in it? False, you would need an atoric lens
When should an atoric lens be recommended and why? when the cyl is 2.00 or higher to improve peripheral vision
What type of lens has a central area with the prescribed power surrounded by an outside area of little or no power? Lenticular
what is the inner part of a lenticular lens called? Aperture
what is the outer part of a lenticular lens called? carrier
How do you find the frame PD? Add the A measurement and the DBL together
What does the Uveal tract consist of? Choroid, Ciliary body, and the Iris
What is the dioptric power of the cornea? +43.00D
What is the axial length of the eye? 24.4mm
The fitting cross is how far above the start of the progressive corridor? 4mm
What type of lens has a spherical front surface and a toric back surface? cylinder lens
When the wearer drops the eyes below the OCs of the lens and vertical prismatic effect of unequal values results for the two eyes, the differential prismatic effect induced is referred to as what? Vertical imbalance
What are a few things to help correct vertical imbalance? contact lenses, dropping the MRP height, fresnel press on prism, and slab off
What part of the lab creates the lens power needed? Surfacing lab
What is the finishing department in a lab responsible for? edging the lens in the frame
In order, list the steps in the edging process? Spotting, Centration, Blocking, then Edging
What point should always appear exactly in front of the wearer's pupil? MRP
A lens is to be edged for a frame with an A dimension equal to 48mm and a DBL equal to 18mm. If the wearer has a PD of 60mm, what is the decentration per lens? 3mm per lens
How much decentration per lens is required to correctly position these lenses for edging? A=52 B=49 DBL=16 PD=70 1mm out per lens
How much decentration per lens is required for an Rx with the following specifications? A=52 B=43 DBL=18 OD PD=32 OD PD=33.5 OD 3mm in OS 1.5mm in
How many rods and cones are there in the eye? 120 million rods and 6 million cones
Aqueous humor is produced by the what? Ciliary body
Light rays pass through a lens and converge at a point 50 cm behind the lens, what is the power? 2.00D
What is the prismatic effect 8 mm below the optical center of a +3.00D lens? 2.4 Base up
A +5.00D lens decentered 2 mm creates how many diopters of prism? 1.00D
A patient wearing 2.00D of prism base up OD and 6.00D base up OS experiences a total prismatic effect of what? 4.00D base up OS
How much prism is generated 8mm from th OC of a +4.00 D lens? 3.2 prism
How far do you decenter a +4.00D lens to create 2 diopter of prism? 5mm
A -4.00 lens must be decentered _____mm to induce 1.00 prism Diopter? 2.5mm
What 4 things affect refraction? curvature, angle of incidence, thickness, and index of refraction
What is snells law used for? to find index of refraction
What is another name for an executive bifocal? the franklin
Where is the OC located on a Franklin bifocal? on the seg height
What type of bifocal has the most amount of image jump? Ultex
What type of bifocal is made of glass and the power in the near is made of a higher index than the carrier? fused bifocal
In a lined bifocal, where is the near OC located? 5mm below the seg
What is another name for slab off? bi-centric grinding
When is it necessary to calculate vertical imbalance? When the patient has 1.50D of anisometropia
For conventional slab off, what type of prism would you order and what lens would you put it in? Base Up Most Minus
For reverse slab off, what type of prism would you order and what lens would you put it in? Base Down Least Minus
What are the steps to calculate slab off? find the power at 90, prentice rule, then difference between the two prisms.
What type of slab off would you use on a glass lens? conventional slab off
What type of slab off would you use on a plastic lens? Reverse slab off
What type of lenses are EXEMPT from the drop ball test? glass, lenticular, slab off, and raised multifocal
When does heat treating not work? plus or minus 7 diopters
What causes the lens to be strong after heat treating? the molecules tense up and creates tension
What happens during chemical tempering? Exchanging ions, sodium and lithium are replaced by potassium
What percent of cyl power is there 60 degrees away from the axis? 75%
What percent of cyl power is there 45 degrees away from the axis? 50%
What percent of cyl power is there 30 degrees away from the axis? 25%
Created by: Kayla Carpenter