# Shared Flashcard Set

## Details

ABO study material
Opticianry Certification
315
Physics
Professional
05/14/2012

## Cards Return to Set Details

Term
 How many millimeters are in an inch?
Definition
 25.4 mm = 1 inch
Term
 What is the spectrum of visible light, in nm?
Definition
 from ~400nm to ~700nm
Term
 List the colors of the spectrum, from longest wavelength to shortest.
Definition
 Red, Orange, Yellow, Green, Blue, Indigo, Violet
Term
 What is the spectrum of UV light, in nm?
Definition
 from ~200nm to ~400nm
Term
 How are the bands in the UV spectrum categorized?
Definition
 A, B, & C (with C being blocked by the Earth's atmosphere)
Term
 What distance is considered at infinity? Why?
Definition
 20 feet- because after light leaves its source, it diverges and becomes parallel at 20 feet
Term
 What is the speed of light?
Definition
 186,000 miles/second
Term
 What happens when light enters a transparent medium at 90 degrees?
Definition
 It slows down and continues onward.
Term
 What happens when light enters a transparent medium at an oblique angle?
Definition
 Refraction- it changes the angle of light
Term
 Each time light encounters a different material, (blank) occurs.
Definition
 Refraction
Term
 Define "Index of Refraction"
Definition
 the degree that light is bent in a given material based on that material's density
Term
 How is Index of Refraction determined?
Definition
 speed of light/speed through the material
Term
 What is the index of refraction of polycarbonate?
Definition
 1.589
Term
 What is the index of refraction of CR39?
Definition
 1.49
Term
 Is material more or less dense with a higher index of refraction?
Definition
 more
Term
 What is the index of refraction of glass?
Definition
 1.523
Term
 What is the index of refraction of flint glass?
Definition
 1.7
Term
 What is the standard index of refraction in the optical industry, which all instruments are calibrated to?
Definition
 1.53
Term
 Define Dispersion
Definition
 when light is broken down into basic colors causing a rainbow effect
Term
 What is abbe value (or Nu value)?
Definition
 measure of how easily dispersion happens
Term
 Abbe values are between what numbers?
Definition
 29 and 60
Term
 Do higher or lower abbe values result in the least dispersion and best vision?
Definition
 higher
Term
 What is the abbe value for plastic?
Definition
 59-60
Term
 What is the abbe value for glass?
Definition
 60
Term
 What is the abbe value for high index resin?
Definition
 43
Term
 What is the abbe value for polycarbonate?
Definition
 29-31
Term
 What is the abbe value for flint glass?
Definition
 38-40
Term
 What 3 things happen as light hits a medium?
Definition
 RefractionAbsorptionReflection
Term
 As light enters and exits any medium, what percent of light is lost (assuming medium is non-coated)?
Definition
 ~8% loss of light (~4% on each surface)
Term
 What is the normal?
Definition
 a line drawn at right angles to the material's surface at the ray's point of entry
Term
 What is the incident ray?
Definition
 the ray coming into the material (before it enters)
Term
 When does the incident ray become the refracted ray?
Definition
 As it enters and leaves the material
Term
 More curve induces (more or less?) refraction
Definition
 more
Term
 What is a diopter?
Definition
 the measure of the power of a lens to refract light
Term
 A lens that can focus parallel light to a point at one meter has what power?
Definition
 1 diopter
Term
 What is the formula for determining diopter power? D=?
Definition
 D = 1/f where f is the focal length of the lens in meters
Term
 How do you determine focal point, given the power of a lens in diopters?
Definition
 f = 1/D
Term
 How do you convert magnification to diopter power?
Definition
 multiply the magnification by 4 (2x is 8 diopters)
Term
 What are the 3 types of plus lens configurations?
Definition
 Bi-convex ()plano convex [)meniscus ))
Term
 What type of lens magnifies an image?
Definition
 plus lens
Term
 What type of lens is thicker in the center and thinner at the edges?
Definition
 plus lens
Term
 What type of lens demonstrates "against" motion (if the lens is moved side to side, the image seems to go the opposite direction)?
Definition
 plus lens
Term
 What are the three types of refractive errors that plus lenses correct for?
Definition
 hyperopiapresbyopiaaphakia
Term
 What are the 3 types of minus lens configurations?
Definition
 Bi-concave )(plano concave )]meniscus ))
Term
 What type of lens minifies an image?
Definition
 minus lens
Term
 What type of lens is thicker at the edges and thinner in the middle?
Definition
 minus lens
Term
 What type of lens demonstrates "with" motion (if the lens is moved side to side, the image seems to go the same direction)?
Definition
 minus lens
Term
 What type of refractive error do minus lenses correct for?
Definition
 myopia
Term
 How do you determine power in diopters using a lens clock?
Definition
 take the front side measurement (usually +) and combine algebraically with the backside measurement (usually -). F + B = P where F= front curve, B= back curve, and P = power
Term
 If the front curve of a lens is clocked at +6 and the back curve is clocked at -5, what is the power of the lens?
Definition
 +1
Term
 How do you transpose an rx?
Definition
 algebraically add the sphere power and the cylinder power to get the new sphere power, use the same cylinder power but switch the sign, and add 90 degrees to the axis
Term
 When prism changes the direction of light, this is known as _________ or _______.
Definition
 diffraction or deviation
Term
 If a prism is strong enough, light can be separated into different colors. This is called ________.
Definition
 dispersion
Term
 Which direction does light entering a prism bend?
Definition
 toward the normal
Term
 The image appears toward the _________ of a prism when looking in while it is actually toward the __________.
Definition
 apexbase
Term
 What measurement is used to indicate the amount of deviation of a prism?
Definition
 diopter
Term
 The ________ a prism, the more light it will bend.
Definition
 larger
Term
 T or F: A prism focuses light.
Definition
 False. A prism only deviates/shifts light, not focuses it
Term
 T or F: A prism does not magnify or minify an image.
Definition
 True. it only shifts/deviates
Term
 Does a steeper angle on a prism result in more or less deviation?
Definition
 more (greater angle of deviation)
Term
 If light passes through the center of a lens, it will neither converge nor diverge. This represents the _________ or the ___________.
Definition
 optical centeraxial ray
Term
 What type of lens converges light?
Definition
 plus lens
Term
 What type of lens diverges light?
Definition
 minus lens
Term
 In a minus lens, if the pupil is below the optical center of the lens, what type of prism is induced?
Definition
 Base down prism
Term
 In a minus lens, if the pupil is above the optical center of the lens, what type of prism is induced?
Definition
 Base up prism
Term
 In a minus lens, if the optical center of the lens is moved toward the nasal, this induces what type of prism?
Definition
 Base out prism
Term
 In a minus lens, if the optical center of the lens is moved toward the temple, this induces what type of prism?
Definition
 Base in prism
Term
 In a plus lens, if the pupil is below the optical center of the lens, what type of prism is induced?
Definition
 Base up prism
Term
 In a plus lens, if the pupil is above the optical center of the lens, what type of prism is induced?
Definition
 Base down prism
Term
 In a plus lens, if the optical center of the lens is moved toward the nasal, this induces what type of prism?
Definition
 Base in prism
Term
 In a plus lens, if the optical center of the lens is moved toward the temple, this induces what type of prism?
Definition
 Base out prism
Term
 What formula determines the prism in a lens at a given point, or how much to decenter a lens to induce prism?
Definition
 Prentice's Formula
Term
 Prentice's Formula
Definition
 P = (h x D)/10P = power in prism dioptersh = OC distance in mmD = dioptric power of lens
Term
 How much prism is induced when a 3D lens is decentered by 5 mm?
Definition
 5x3/10 = 1.5 diopters of prism
Term
 How much prism is induced in a -4.25 lens decentered by 4 mm?
Definition
 4 x -4.25/10 = 1.7 diopters of prism
Term
 How much prism is a person inducing if he looks 6 mm below the OC in a lens -3.00 -3.25 x 180?
Definition
 3.75 diopters of prism*use power at 90 degrees since shifting down, which is -6.25
Term
 How far is a lens moved to have 5D of prism in a 2D power lens?
Definition
 (5*10)/2=h25 mm = h
Term
 Given a +2.00 -5.00 x 180, how far must the lens be decentered to get 1 BU prism and in what direction?
Definition
 (1*10)/-3.00 = 3.3 mm*power at 90 degrees is -3.00. for minus lens, BU prism is induced by moving OC down
Term
 A pair of glasses has been found to be 4 mm off in the PD. OD: -2.00 +2.00 x 90OS: -0.75 sphWhat is the prism induced?
Definition
 OD: P= (2x0)/10 = 0 dioptersOS: P= (2 x -0.75)/10 = .15 diopters prism*assume off by 2 mm in each eye*OD at 180 degrees is plano
Term
 How many diopters of difference between eyes will induce double vision when looking away from the optical center?
Definition
 2+ diopters of difference
Term
 What is another name for slab off prism?
Definition
 bicentric grinding
Term
 When 2 separate optical centers are ground into one lens, what is it called?
Definition
 slab off prism or bicentric grinding
Term
 How do you determine which eye slab off prism should be done in?
Definition
 the most minus (or least plus) lens
Term
 If a patient has an RX of OD +2.00 sph and OS +0.25 -4.00 x 135, which eye should have slab off prism?
Definition
 the left eye (it is the most minus)
Term
 OD: +2.00OS: +5.00What amount of prism will a patient experience with a reading gaze 10 mm below the OC with this RX?
Definition
 OD: 2x10/10= 2D BU prismOS: 5x10/10= 5D BU prism
Term
 What is diplopia?
Definition
 double vision
Term
 Why don't you need to use slab off prism with single vision lenses?
Definition
 patient can move head to look through OC
Term
 OD: -2.00 -2.00 x 135 +2.50OS: +2.00 -0.50 x 45 +2.50Patient is ordering a FT28 in a 56/17 metal frame and has a PD of 68. Seg ht is 15. The OC difference between the distance and near is 12 mm.1. What is the total prism needed for a slab off?2. Which side will the slab off be on?3. Which side would the slab off be on if it were reverse slab?
Definition
 *power at 90 degrees for each lens isOD: -3.00, OS: +1.75*difference in power is 4.75D1. using Prentice's rule (h=12, D=4.75)12x4.75/10=5.7 diopters prism2. OD3. OS
Term
 What is the RX for the split prism version of this RX?OD: -0.50 3 BDOS: -1.00
Definition
 OD: -0.50 1.5 BDOS: -1.00 1.5 BU
Term
 What is the RX for the split prism version of this RX?OD: -1.00 -1.00 x 90 5 BUOS: -1.25 -2.50 x 90 3 BO
Definition
 OD: -1.00 -1.00 x 90 2.5 BU 1.5 BOOS: -1.25 -2.50 x 90 2.5 BD 1.5 BO
Term
 When splitting prism, base out and base in are split in what direction?
Definition
 the same direction (both eyes BO or both eyes BI)
Term
 When splitting prism, base up and base down are split in what direction?
Definition
 opposite directions (one eye of each)
Term
 How many tunics (layers) make up the outer part of the eye? What are they (listed from outermost to innermost)?
Definition
 3- fibrous tunic, vascular tunic, and nervous tunic
Term
 What is the name of the outer tunic of the eye that is mostly composed of dense connective tissue?
Definition
 The fibrous tunic
Term
 The fibrous tunic is divided into the __________ and the ____________.
Definition
 sclera, cornea
Term
 How much refractive power (in diopters) does the cornea have?
Definition
 43 diopters
Term
 Which outer tunic contains the blood vessels that supply the retina with nutrients?
Definition
 choroid tunic
Term
 What is the name for the white part of the eye?
Definition
 sclera
Term
 What part of the eye is translucent and serves as a passageway for light to enter the eye?
Definition
 cornea
Term
 Which tunic is also known as the choroid tunic?
Definition
 vascular tunic
Term
 The ___________ helps to refract light and to focus on the retina.
Definition
 cornea
Term
 What layer contains a high concentration of dark pigments that help absorb excess light?
Definition
 choroid
Term
 The _________ is primarily composed of nerve tissue and forms a thin internal membrane of the eye.
Definition
 retina
Term
 The vascular tunic consists of...?
Definition
 iris, choroid, & ciliary body
Term
 The inner layer of photoreceptors and neurons (the nervous tunic) consists of...?
Definition
 the retina
Term
 How many segments/chambers are contained within the inner part of the eye? What are they?
Definition
 3- anterior chamber, posterior chamber, & vitreous chamber
Term
 The fluid filled area between the cornea and the iris is the ________.
Definition
 anterior chamber
Term
 The fluid filled area between the iris and the lens is know as the __________.
Definition
 posterior chamber
Term
 The anterior and posterior chambers contain a fluid known as _____________.
Definition
 aqueous humour
Term
 Define aqueous humour.
Definition
 watery fluid produced in ciliary body which fills the anterior and posterior chambers that maintains pressure in the eye and provides nutrients to the lens and cornea
Term
 Aqueous humor is continually drained from the eye through the ____________.
Definition
 Canal of Schlemm
Term
 The greatest volume of the inner chambers, forming about four-fifths of the eye, is the ________________.
Definition
 vitreous chamber
Term
 The vitreous chamber is found between the _________ and the __________.
Definition
 retina, lens
Term
 What is vitreous humour?
Definition
 a thicker gel-like substance contained within the vitreous chamber which maintains the shape of the eye
Term
 What does vitreous humour do?
Definition
 maintains the shape of the eye
Term
 What does aqueous humour do?
Definition
 maintains IOP, provides nutrients to the lens and cornea
Term
 The cornea consists of how many distinct layers?
Definition
 5epitheliumBowman's MembraneStromaDescemet's MembraneEndothelium
Term
 The outermost layer of the cornea is called the ___________.
Definition
 epithelium
Term
 The outermost layer of the cornea, the epithelium, rests on ______________.
Definition
 Bowman's Membrane
Term
 The _________ and the ____________ serve to protect the cornea from injury.
Definition
 epithelium, Bowman's Membrane
Term
 The ____________ protects the cornea through its ability to quickly regenerate.
Definition
 epithelium
Term
 ___________ protects the cornea by providing a tough, difficult to penetrate barrier
Definition
 Bowman's Membrane
Term
 The innermost layer of the cornea which rests on Descemet's Membrane is called the ___________________.
Definition
 endothelium
Term
 What is the function of the endothelium?
Definition
 It removes water from cornea, helping to keep the cornea clear.
Term
 What layer of the cornea accounts for 90% of its thickness?
Definition
 the stroma
Term
 The __________ controls how much light enters the pupil.
Definition
 iris
Term
 How many muscles are found in the iris? What are their names?
Definition
 2- dilator muscle and sphincter muscle
Term
 The ________ muscle opens the pupil, allowing more light into the eye.
Definition
 dilator
Term
 The ___________ muscle closes the pupil, restricting light into the eye
Definition
 sphincter
Term
 The ___________ is just behind the pupil. Its purpose is to focus light on the retina.
Definition
 crystalline lens
Term
 Define accommodation.
Definition
 the process of focusing on objects based on their distance
Term
 The __________ surround the lens, helping it achieve accomodation.
Definition
 Ciliary Body
Term
 What are zonules?
Definition
 fibrous strands that attach the ciliary body to the lens
Term
 Describe the process of how the lens allows the eye to focus up close.
Definition
 the ciliary body contracts and the zonules relax, allowing the lens to thicken and add power
Term
 Describe the process of how the lens allows the eye to focus at distance.
Definition
 the ciliary body relaxes and the zonules contract, drawing the lens outward, making the lens thinner and decreasing power
Term
 The retina consists of photoreceptor cells called _______ and ________.
Definition
 rodscones
Term
 Which photoreceptor cells are the more numerous ones (apprx. 120 million)?
Definition
 rods
Term
 Which photoreceptor cells are contained mostly at the periphery?
Definition
 rods
Term
 Which photoreceptor cells are suited to night vision and peripheral vision?
Definition
 rods
Term
 Which photoreceptor cells have the primary function of detail and color detection?
Definition
 cones
Term
 Which photoreceptor cells are the less numerous ones (apprx. 6 million)?
Definition
 cones
Term
 Which photoreceptor cells are largely concentrated in the fovea?
Definition
 cones
Term
 How many types of cones are there? Describe them.
Definition
 3- Each type receives only a narrow band of light corresponding largely to a single color.
Term
 What colors do the three types of cones correspond to?
Definition
 red, green, or blue
Term
 The signals received by the cones are sent via the ________ to the brain where they are interpreted as color
Definition
 optic nerve
Term
 _________ refers to an eye free of refractive errors.
Definition
 emmetropia
Term
 Define myopia. When does it occur?
Definition
 near-sightednessIt occurs if the eye is longer than normal or the curve of the cornea is too steep, causing light rays focus in front of the retina.
Term
 What type of refractive error causes light rays to focus in front of the retina?
Definition
 myopia
Term
 Define hyperopia. When does it occur?
Definition
 far-sightednessIt occurs if the eye is too short or the curve of the cornea is too flat, causing light rays to focus behind the retina.
Term
 What type of refractive error causes light rays to focus behind the retina?
Definition
 hyperopia
Term
 When does astigmatism occur?
Definition
 It occurs when the cornea has an oblong, football-like shape in one or more directions (or axes) causing light rays to focus on more than one point on the retina.
Term
 What type of refractive error causes light rays to focus on more than one point on the retina?
Definition
 astigmatism
Term
 When does presbyopia occur?
Definition
 When, because of aging, the crystalline lens begins to lose elasticity and is no longer able to accomodate to focus at near points.
Term
 Around what age does presbyopia occur?
Definition
 begins at 40
Term
 Around what age is the loss of elasticity of the crystalline lens complete?
Definition
 65
Term
 What is the term for the condition in which two eyes have unequal refractive power.
Definition
 Anisometropia
Term
 _________is an extreme case of anisometropia where one eye is myopic and the other is hyperopic.
Definition
 Antimetropia
Term
 The unequal refractive states in antimetropia can lead to __________ and ___________.
Definition
 diplopia (double vision) asthenopia (eye strain)
Term
 If there is a large difference between the two eyes, the brain will often suppress the vision of the blurrier eye. What is this condition called?
Definition
 amblyopia
Term
 What is the name of the group of muscles responsible for the stabilization of eye movement?
Definition
 extraocular muscles
Term
 How many extraocular muscles are there? Name them.
Definition
 6:Lateral rectusMedial rectusSuperior rectus Inferior rectusSuperior obliqueInferior oblique
Term
 What is the name of the muscle that moves the eye outward, away from the nose?
Definition
 Lateral rectus
Term
 What is the name of the muscle that moves the eye inward, toward the nose?
Definition
 Medial rectus
Term
 What is the name of the muscle that moves the eye upward and slightly outward?
Definition
 Superior rectus
Term
 What is the name of the muscle that moves the eye downward and slightly inward?
Definition
 Inferior rectus
Term
 What is the name of the muscle that moves the eye outward and downward?
Definition
 Superior oblique
Term
 What is the name of the muscle that moves the eye outward and upward?
Definition
 Inferior oblique
Term
 What is diplopia?
Definition
 double vision
Term
 Difficulty with fusion can cause double vision (diplopia), or it can cause the brain to "turn off" one image in an effort to eliminate diplopia. This condition is called ____________.
Definition
 suppression
Term
 What is suppression?
Definition
 When one of more of the extraocular muscles are either too strong or too weak, causing difficulty with image fusion. Suppression results when the brain "turns off" one image in order to eliminate double vision.
Term
 Define phoria.
Definition
 when the eye has a tendency to turn from its normal position (such as when the patient is tired)
Term
 Define tropia.
Definition
 when the eye has a definite or obvious turning from its normal position
Term
 What is it called when the eye has a tendency to turn downward?
Definition
 hypophoria
Term
 What is it called when the eye has a tendency to turn inward?
Definition
 esophoria
Term
 What is it called when the eye has an obvious upward deviation?
Definition
 hypertropia
Term
 What is it called when the eye has an obvious outward deviation?
Definition
 exotropia
Term
 What is the name of electromagnetic radiation that lies just above the visible spectrum (750nm-1mm)?
Definition
 infrared
Term
 What is the name of electromagnetic radiation that lies just below the visible spectrum (1nm-400nm)?
Definition
 ultraviolet
Term
 List the types of electromagnetic radiation in order of increasing wavelength.
Definition
 gamma raysx raysUVVisible spectrum (VIB G YOR)InfraredMicrowaveRadio waves (FM-AM)Long radio waves
Term
 What notation is used to indicate index of refraction?
Definition
 n
Term
 What is the index of refraction (n) of air?
Definition
 1
Term
 What is the index of refraction (n) of vitreous humour?
Definition
 1.33
Term
 What is the index of refraction (n) of aqueous humour?
Definition
 1.33
Term
 What is the index of refraction (n) of the cornea?
Definition
 1.37
Term
 What is the index of refraction (n) of the crystaline lens?
Definition
 1.42
Term
 What is the index of refraction (n) of CR-39?
Definition
 1.49
Term
 What is the index of refraction (n) of crown glass?
Definition
 1.52
Term
 What is the index of refraction (n) of polycarbonate?
Definition
 1.58
Term
 Light rays pass through a lens and converge 0.50 m from the lens. What is the power of the lens?
Definition
 P=1/f = 1/.5 = 2D
Term
 What is the ideal base curve for a mild rx (-1.75 to +2.00)?
Definition
 6
Term
 For plus powers, base curves should ideally be __________ than 6.
Definition
 more
Term
 For minus powers, base curves should ideally be __________ than 6.
Definition
 less
Term
 What would be the ideal base curve for moderate plus powers (+2.25 to +5.25)?
Definition
 8
Term
 What would be the ideal base curve for high plus powers (+5.50 to +8.75)?
Definition
 10
Term
 What would be the ideal base curve for very high plus powers (+9.00 to +10.50)?
Definition
 12
Term
 What would be the ideal base curve for super high plus powers (+10.75 to +12.25)?
Definition
 14
Term
 What would be the ideal base curve for extremely high plus powers (+12.25 and up)?
Definition
 16
Term
 What would be the ideal base curve for moderate minus powers (-2.00 to -4.50)?
Definition
 4
Term
 What would be the ideal base curve for high minus powers (-4.75 to -8.00)?
Definition
 2
Term
 What would be the ideal base curve for very high minus powers (-8.00 to -9.00)?
Definition
 0.5
Term
 What would be the ideal base curve for super high minus powers (-9.00 and up)?
Definition
 plano or minus
Term
 A lens clock is calibrated to read materials with a refractive index of __________.
Definition
 1.53
Term
 Hi-index materials will have true power _________ than the measurement given by a lens clock. Why is this?
Definition
 greater thanThe lens clock is calibrated to read materials with a refractive index of 1.53
Term
 Using a lens clock, if we find the curve on the front surface of the lens to be +6.00 D and determine the back surface to be toric with a measurement of -8.00 D in the 90ΒΊ meridian and -5.00 in the 180ΒΊ meridian, what is the true power of the lens?
Definition
 +1.00 -2.00 x180
Term
 How many types of refractive errors are there? What are they?
Definition
 7HyperopiaMyopiaSimple hyperopic astigmatismSimple myopic astigmatismCompound hyperopic astigmatismcompound myopic astigmatismmixed astigmatism
Term
 _____________ has a plano meridian with a plus meridian.
Definition
 simple hyperopic astigmatism
Term
 _____________ has a plano meridian with a minus meridian.
Definition
 simple myopic astigmatism
Term
 _____________ has two plus meridians.
Definition
 compound hyperopic astigmatism
Term
 _____________ has two minus meridians.
Definition
 compound myopic astigmatism
Term
 _____________ has one plus and one minus meridian.
Definition
 mixed astigmatism
Term
 What type of refractive error is the following rx?-1.00 -1.50 x079
Definition
 compound myopic astigmatism
Term
 What type of refractive error is the following rx?+1.00 -1.00 x126
Definition
 simple hyperopic astigmatism
Term
 What type of refractive error is the following rx?pl -2.50 x008
Definition
 simple myopic astigmatism
Term
 What type of refractive error is the following rx?+5.25 -2.50 x169
Definition
 compound hyperopic astigmatism
Term
 What type of refractive error is the following rx?+0.75 -2.50 x098
Definition
 mixed astigmatism
Term
 What type of refractive error is the following rx?+3.00 sph
Definition
 hyperopia
Term
 What type of refractive error is the following rx?-2.50 sph
Definition
 myopia
Term
 What material accepts tint best?
Definition
 CR-39
Term
 ____________ is twice as heavy as CR-39 but very durable.
Definition
 crown glass
Term
 The tints available with glass are...?
Definition
 grays, photochromics, pinks, some browns and greens
Term
 Why is UV coating not applied to glass?
Definition
 gives it a yellow tint
Term
 ____________ is the recommended material for safety glasses.
Definition
 polycarbonate
Term
 Plus cylinder- when the cylinder is surfaced on the front of the lens rather than the back- is mainly used in what circumstance?
Definition
 diving masks when power calls for a plus lens with cylinder
Term
 _________ are added to glass to create basic tints.
Definition
 metallic oxides
Term
 __________ are added to glass to create photochromic effects.
Definition
 silver halides
Term
 _________ is the original material used to make AR coatings.
Definition
 magnesium flouride
Term
 AR coatings work through ______________.
Definition
 destructive interference
Term
 A plano base curve should be used on what powers?
Definition
 -6.00 and up
Term
 A 2.00 base curve should be used on what powers?
Definition
 -4.00 to -6.00
Term
 A 4.00 base curve should be used on what powers?
Definition
 -2.00 to -4.00
Term
 A 6.00 base curve should be used on what powers?
Definition
 -2.00 to +2.00
Term
 A 8.00 base curve should be used on what powers?
Definition
 +2.00 to +4.00
Term
 A 10.00 base curve should be used on what powers?
Definition
 +5.00 to +8.00
Term
 A 12.00 base curve should be used on what powers?
Definition
 +8.00 and up
Term
 Specific gravity describes what?
Definition
 the density of a material by comparing its density to the density of water
Term
 The higher the specific gravity of a lens material, the _________ the density, and consequently, the ________ a lens of that material will be for a given power and size.
Definition
 higherheavier
Term
 What is the standard fitting distance for a reading power?
Definition
 16 inches or 40 cm
Term
 The standard fitting distance for the intermediate distance in a trifocal is generally _________.
Definition
 30 inches
Term
 The intermediate distance in a trifocal is ________ % of the add power.
Definition
 50%
Term
 Where is the fitting height measured for a bifocal?
Definition
 lower lid line
Term
 Where is the fitting height measured for a trifocal?
Definition
 bottom of the pupil
Term
 What type of bifocal is the heaviest?
Definition
 executive
Term
 Is image jump greater in round top or flat top bifocals?
Definition
 round tops
Term
 What is the power through the intermediate segment of a trifocal lens with the following rx?+0.50 +1.00 x043 Add: 2.50
Definition
 +1.75 +1.00 x043
Term
 Image jump will be more dramatic in a bifocal when ____________.
Definition
 The OC of the distance area and the OC of the reading portion are far apart
Term
 Progressives are fit at what point?
Definition
 pupil center
Term
 If a patient has cataract surgery and the crystalline lens is removed and not replaced with an implant, the patient will need what type of lens to compensate?
Definition
 full field and aspheric lenticular
Term
 What power range is usually used for lenses for a cataract patient after surgical removal of the crystalline lens?
Definition
 +10.00 to +16.00 or more
Term
 As a lens moves away from the eye, it becomes more _________.
Definition
 plus
Term
 As a lens moves closer to the eye, it becomes more ________.
Definition
 minus
Term
 Modification to a power should be made to accommodate for change in effective power at what point?
Definition
 7.00 diopters or more
Term
 If a lens sits closer to a patient's eye than the distance at which he was refracted, the power should be altered in what way?
Definition
 more plus
Term
 What is the standard instrument vertex?
Definition
 14mm
Term
 For a +10 power lens, every millimeter closer vertex distance should result in approximately ______ diopters of ________ power.
Definition
 .1 additional
Term
 When light enters a prism, shorter wavelengths are bent to a __________ degree than longer wavelengths.
Definition
 greater
Term
 Define chromatic aberration.
Definition
 the tendency of a material to separate/disperse light that enters it into its various colors
Term
 A material's level of chromatic aberration can be gauged by its ___________.
Definition
 abbe value
Term
 The Abbe value of a material is __________ proportional to the chromatic aberration induced as light passes through it.
Definition
 inversely
Term
 Generally speaking, the _______ the index of a lens material, the _______the chromatic aberration, and the _________ the Abbe value.
Definition
 higherhigherlower
Term
 The __________ of the material describes the percentage of incident light reflected from a highly polished surface of that material and is calculated from the refractive index of a material
Definition
 reflectance
Term
 What is the formula used to determine reflectance:When light hits a lens surface in air normally, the percentage of light reflected at each surface is calculated using this formula.
Definition
 R = (n - 1)^2/(n + 1)^2 * 100%where R = reflectanceand n = refractive index of material
Term
 Calculate the reflectance of polycarbonate
Definition
 R = (1.58-1)^2/(1.58+1)^2R = .3364/6.6564R = .05054 = 5.054% per surface
Term
 The ____________ of a lens material describes the amount of light (usually specified for a given waveband) that will pass through that material.
Definition
 transmittance
Term
 ________is most stable, scratch-resistant, and provides the best optical quality of all lens materials.
Definition
 glass
Term
 What type of aberration is more pronounced in high-index glass than regular glass?
Definition
 chromatic aberration
Term
 Name 3 positive aspects of glass lenses.
Definition
 best opticsstable materialscratch resistant
Term
 Name 3 negative aspects of glass lenses.
Definition
 difficult to tintlacks impact resistance (too brittle)heaviness
Term
 Glass is ____x heavier than plastic.
Definition
 2
Term
 Name 3 positive aspects of CR-39 lenses.
Definition
 easily tintablelighter than glassless likely to fog
Term
 Name 2 negative aspects of CR-39 lenses.
Definition
 more susceptible to scratchinglower index of refraction than glass
Term
 Name 3 positive aspects of polycarbonate lenses.
Definition
 impact resistantthinner & lighter than plasticinherent UV protection
Term
 Name 4 negative aspects of polycarbonate lenses.
Definition
 not easily tintedsoft (scratches easily)poor opticssusceptible to stress fractures in drill mounts
Term
 What are the benefits of aspheric lenses?
Definition
 reduced spatial distortionreduced magnification or minificationmaintains a thin and flat lens profile
Term
 Patients who are sensitive to chromatic aberration may have issues with which types of lens materials?
Definition
 polycarbonatehigh-indexpossibly trivex
Term
 What is the abbe value of trivex?
Definition
 43-45
Term
 What is the index of refraction of trivex?
Definition
 1.53
Term
 What materials have natural UV protection?
Definition
 trivex & polycarbonate
Term
 What is the lightest lens material available?
Definition
 Trivex (specific gravity of 1.11)
Term
 What are the positive aspects of trivex?
Definition
 Impact resistance of polycarbonate Better optics than polycarbonate Tintable Lightest material on the marketInherent UV protectionHigh tensile strength (ideal for drill mounts)
Term
 [image]
Definition
Term
 Internal reflections viewed as multiple rings inside the lens are most common with what type of lens?
Definition
 high minus
Term
 Blurred or ghost images due to light reflection within a lens can significantly impair vision, especially during what situation?
Definition
 at night around bright lights common in dusk or night time driving conditions
Term
 Bright sun light hitting the back surface of a sun lens that is not AR coated, depending on the angle, can either ________________ or can ________________.
Definition
 be reflected directly back into the eye"fill" the lens with reflected light
Term
 _____________ allow more light to reach the eye increasing contrast and clarity as well as help to reduce eye strain.
Definition
 AR coatings
Term
 Polarized lenses significantly increase driving safety, especially at what times?
Definition
 morning and late afternoon
Term
 What is a good analogy to use to describe how polarized lenses work?
Definition
 venetian blinds- they force the light to enter only at a certain angle
Term
 Why is polarization better than tinting?
Definition
 Although tinting reduces brightness and therefore increases wearer comfort, it doesn't reduce glare like polarization does.Also, tinting can be actually lead to increased UV damage since the eyes dilate behind the dark tint and allow more light in. Polarization blocks harmful UV rays.
Term
 These type of coatings are produced relatively cheaply. They are applied by dipping the lens into a chemical solution and curing the lens in an oven.
Definition
 Dip-Coating
Term
 These coatings are applied to a spinning lens. The lenses must be cured after the hardcoat chemicals are applied. The curing can be done in an oven or by ultraviolet light.
Definition
 Spin-Coating
Term
 These coatings are made by adding the hardcoat chemical at the time that the lenses are being formed. Most lens manufacturers are using this type of coating process. This process is generally used on semi-finished lenses only. These coatings tend to be non-tintable.
Definition
 In-mould Coating
Term
 This is a process that is becoming more popular with the rise in anti-reflective coating use. The cost is generally much higher than the other methods. When this type of hard coat is produced at the same time and in conjunction with an anti-reflective coating, the costs difference is not as prohibitive.
Definition
 Vacuum Coatings
Term
 These are highly reflective coatings and are used to reduce the light transmission through a lens. They are produced in a vacuum process.
Definition
 Mirror Coatings
Term
 What is the desired vertex distance when fitting a pair of glasses?
Definition
 10-14mm
Term
 What is the best range for degree of face form when fitting a pair of glasses?
Definition
 5-10 degrees
Term
 What is the desired range for pantoscopic tilt when fitting a pair of glasses?
Definition
 10-15 degrees
Term
 When the lenses are ground to specification, the lab will often incorporate prism. What is this process called?
Definition
 equi-thinning, prism thinning, or yolk prism
Term
 What is the focal distance used for a lens meant for computer use?
Definition
 20-24 inches (50-60 cm)
Term
 What is the focal distance used for a lens meant for reading?
Definition
 14-18 inches (35-45 cm)
Term
 What is the minimum center thickness for a basic impact safety lens?
Definition
 3 mm
Term
 What is the minimum edge thickness for a basic impact safety lens?
Definition
 2.5 mm (if it is +3.00 diopters or higher)
Term
 A basic impact safety lens must pass what type of test?
Definition
 a drop ball test of a 1 inch diameter steel ball dropped 50 inches
Term
 What is the minimum center thickness for a high impact safety lens?
Definition
 2.5 mm
Term
 A high impact safety lens must pass what type of test?
Definition
 a high velocity test in which a ΒΌ inch steel ball is shot at a lens at 150 ft/second
Term
 What are the material options for a high impact safety lens?
Definition
 polycarbonate, Trivex, or SR-91
Term
 How can you tell if a frame is impact resistant enough to be considered a safety frame?
Definition
 marked with "Z87+" on the frame front and temple.
Term
 What is the chassis?
Definition
 The frame front
Term
 What are guard arms?
Definition
 the wires that attach the nosepads to the frame
Term
 What is the endpiece?
Definition
 the area of the chassis that attaches to the temple
Term
 What is the ideal amount of pantoscopic tilt for most frames?
Definition
 8-10 degrees
Term
 What is orthoscopic tilt?
Definition
 when a frame has 0 degrees of pantoscopic tilt (no tilt)
Term
 What is retroscopic tilt?
Definition
 when a frame is farther from the patient's face at the bottom of the lens than it is at the top
Term
 What are the 4 basic adjustments that can be made to nosepads?
Definition
 widthsplay anglefrontal anglevertical angle
Term
 What is splay angle?
Definition
 the angle of the pads when viewed from the top of the frame- the front edges of the pads should be closer together than the back edges
Term
 What is frontal angle?
Definition
 the angle of the pads when viewed from the front of the frame- the tops of the pads should be slightly closer together than the bottoms of the pad following the contours of the nose as it gets wider from top to bottom
Term
 What is vertical angle?
Definition
 the angle of the pads when viewed from the side of the frame. Since most frames will have some amount of pantoscopic tilt, the bottoms of the pads should be slightly closer to the frame front than the tops
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