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LDO Review Contacts

QuestionAnswer
The central posterior curve is also known as what? Base curve and optical zone
The back surface of the lens that has the base curve ground into it and is used for the fitting and power is called what? Optical Zone
What lies between the base curve and the peripheral curve on the posterior lens surface? Secondary curve or intermediate curve
What is the outermost curve on the posterior lens surface? Peripheral curve
What is the treatment given to the sharp junctions between the base curve, secondary curve, and peripheral curve? Blending
the overall width of the lens from one edge to the other and is measured in mm is called what? Diameter
what is the measurement taken from the anterior surface to the posterior surface of the lens at its geometric center? Center thickness
What is the curvature that determines the lens power? Anterior optical zone radius
The difference between the radii of the anterior and posterior lens surfaces creates what? Lens power
What does lenticular flange do to a contact lens? Aid in lens positioning by increasing or decreasing edge thickness
When a contact lens sits low on the cornea would you increase or decrease the edge thickness? Increase
When angulation is placed on the front surface of a lens to reduce edge thickness and decrease lid sensation its called what? CN Bevel or hyper flange
Would you do a CN bevel for a high minus or high plus lens. High minus
What is designated to limit lid irritation and keeps the posterior surface away from the cornea? Lens edge
The edge of a lens has 3 zones, what are they? Anterior, posterior, and edge apex.
What is the addition of plastic to the base of the anterior lens surface? Prism Ballast
What is the purpose of prism ballast? Aids in proper orientation of astigmatic and bifocal lenses
Removal of the inferior and/or superior portions of the lens to aid in orientation and stabilization is called? Trunction
In a _________ lens design, the radius of curvature is the same in all meridians. Spherical lens design
What lens design has a spherical posterior surface curvature with a toric anterior curve? Front surface toric design
What lens design has a toric posterior curvature with two principle meridians 90 degrees apart and the anterior lens surface is spherical? Back surface toric design
What lens design has toric curvatures on both the anterior and posterior surfaces, with principle meridians 90 degrees apart? Bitoric lens design
The distance between the posterior surface of the central area of the lens and the flat surface is called what? Sagittal depth
What are the movable folds that protect the eye from injury, light, and keep the eye moist by spreading tear film? Eyelids
What is the space between the two open eyelids called? Palpebral fissure
What is the main support structure of the eyelids? the tarsal plates
What does the lacrimal gland do? produce tears
Where do the tears drain from the eye? upper and lower punctums
What is attached to the punctum that the tears drain into? the lacrimal sac
What are the layers of the tear film? lipid, aqueous, and mucous
What are 2 functions of the tear film? forms a smooth refractive surface on the cornea and carries oxygen to the eye
How would increasing the diameter change the fit of the lens? tighten the fit
How would decreasing the diameter change the fit of the lens? loosen and flatten the lens
The ability of the contact lens surface to wet can be described by it what? Wetting angle
The amount of oxygen that the lens will allow through is measured by its what? DK Value
What was the first hydrogel lens polymer used for contacts? HEMA
What is the transitional zone from the cornea to the sclera called? Limbus
Why would you use a prism ballast on a contacts lens? to prevent rotation
what is the reciprocal of the focal length of an optical surface, lens, or system? Vertex power
How long does it take a rigid lens wearer to adapt to the way their contacts feel? 2 weeks
When doing keratometry, what is the first thing you need to do? focus the eyepiece
Is the tear break-up time test included in the pre-fitting evaluation? Yes
What instrument is used to evaluate the fit of the contact lens? Slit-Lamp
What dye is used to evaluate corneal stains? Fluorescein
What type of slit-lamp illumination is it when the beam of light is opened to its widest point? Diffuse illumination
When do you use a diffuse illumination? used for a general survey of the eye and for evaluating corneal staining under the blue light with fluorescein dye.
what type of slit-lamp illumination is it when the examiner looks directly at the beam of light and adjusts it to 1-3mm wide? Direct illumination
When do you use direct illumination? used for judging the fit of the contact lenses
What filter is used to verify fluorescein patterns? cobalt blue filter
What is the ideal fluorescein staining pattern? where the center of the lens is faint green and the peripheral is bright green
what would a steep fluorescein pattern look like? fluorescein pooling in the center of the lens and faint green in the mid periphery
What would a flat fluorescein pattern look like? Very faint green in apex of the lens and pooling in the periphery
What modification would be needed for a lens that has central pooling? decrease the diameter for a looser fit or use a flatter base curve
What modification would be needed for a lens that has peripheral pooling? increase the diameter for a tighter fit or use a steeper base curve
What is the biggest advantage soft lenses have over rigid lenses? Initial comfort
If a patient has Irregular Astigmatism, what type of contact lens material would you fit them in? RGP
What is it called when a patient develops an allergic reaction to deposits on the lenses, resulting in inflammation and bumps on the upper lid? GPC
What is the benign yellowish nodule found within the palpebral fissure, just outside the limbus on the conjunctiva called? Pinguecula
What are some disadvantages of high water content lenses? decreased optics and attracts more deposits
What are some advantages of high water content lenses? Softer and better initial comfort
What does the FDA classify material by? Water content and electronic charge
What 2 characteristics affect oxygen transmission? Water content and thickness
What are some advantages of thicker lenses? easier handling, durability, and visual stability
What is a disadvantage of thicker lenses? Comfort
What is the main factor in lens comfort? edge design
What is the draping effect? the ability of the lens to conform to the shape of the eye
In soft lens fitting, the perfect relationship is described as what? the three point touch
What is the three point touch? the lens touches the center and the two opposite edges from the center in any given direction
The curvature of the lens is dictated by the curvature of the what? Cornea
The average corneal curvature is between _____ and _____? 42.00D and 45.00D
Is it recommended to start with flat or steep fitting lenses first? Flat
For a spherical prescription when do you need to compensate for vertex distance? +or -4.00D or greater
If the spectacle prescription is -2.50D, what is the contacts lens prescription going to be? -2.50D
If the spectacle prescription is +1.00D, what is the contacts lens prescription going to be? +1.00D
When is it necessary to use a toric contact lens? when the cyl is 1.00 or more
Starting at 4.00D, for every 2D of power change how much does the vertex factor change? +0.25D
From the spectacle Rx -6.00D, what would the contact lens Rx be? -5.50D
From the spectacle Rx +8.25D, what would the contact lens Rx be? +9.00D
From the spectacle Rx -1.00D, what would the contact lens Rx be? -1.00D
From the spectacle Rx -10.00D, what would the contact lens Rx be? -9.00D
From the spectacle Rx -3.00-0.50x090, what would the contact lens Rx be? -3.25D
Which BC is flatter 8.4 or 8.6? 8.6
A certain brand of contacts are available in 8.0, 8.4, and 8.7 BC with a 14.0 diameter. Which base curve should be selected first? 8.7
After lens insertion, how long should you let the lenses settle? 20 minutes
For any soft lens fit to be considered successful what five criteria must be met? complete corneal coverage, adequate movement, three point touch, good visual acuity, and patient comfort?
How far should the contact extend onto the sclera? 1mm
How much lens movement is recommended upon blinking? .5mm to 1mm
How do you evaluate the lag of a contact lens? In the slit lamp, instruct the patient to look up, down, left, and right evaluating how much the contact lags behind.
What parameters must be included when ordering a soft lens? Base curve, power, diameter, and tint
What are the 2 most adverse affects to wearing soft lenses? lens dryness and surface deposits
When not using fluorescein dye, what instrument is best used to verify the three point touch? Kerotometer
What machine is used to verify base curve and optical quality of a lens? Radiuscope
What is the flattest curve on a contact lens? Posterior peripheral curve
What is the ideal finished edge thickness? between .08mm and .12mm, measured from .5mm in form the lens edge
What do you use to verify the lens diameter? A diameter gauge or measuring magnifier
A lens surface that gets progressively flatter from center to edge is called what? Aspheric
What hydrogel lens material has a polymer made up of repeating hydroxyethyl methacrylate monomer units? HEMA
What polymer absorbs and binds water into its molecular structure? Hydrogel
What does hydrophilic mean? Water loving
What is another name for a lens blank? a button
Any curve that is applied outside of the optical zones of the lens posterior or anterior surfaces is called what ? peripheral curve
What rigid, non-permeable contact lens material has a polymer made up of polymethyl methacrylate? PMMA
What is a small chemical unit, or monomer, linked together to form a repeating chemical chain of high molecular weight? a polymer
What is the central anterior curve of a contact lens? power curve
What is an oxygen permeable contact lens plastic whose main ingredients are silicone(for permeability) and methyl methacrylate(for durability and stability)? silicone acrylate
What is the first thing that should be covered on the dispensing visit? proper lens care and handling
How many hours should a new soft lens wearer wear the contacts on the first day? 4 hours
How many hours of wearing time should a new soft lens wearer increase each day? 2 hours
What are some of the adaptive symptoms in soft lens wear? tearing upon insertion, mild foreign body sensation, mild photophobia, and sometimes a slight headache.
What are some abnormal symptoms in soft and rigid lens wear? persistent pain, burning and excess tearing, redness that does not clear up, hazy vision, and sensitivity to light
If a patient accidentally sleeps in their contacts what should be the first thing they do upon awakening? lens lubricant to loosen the lens
How many hours should a new rigid lens wearer wear the contacts on the first day? 3 hours
How many hours of wearing time a should a new rigid lens wearer increase each day? 1 hour
What are some adaptive symptoms in rigid lens wear? tearing upon insertion, lid irritation, excessive blinking, and difficulty looking up
What does the subjective examination include at the follow up exam? taking the patient history. what they liked and didn't like about the contacts
What should the objective examination include? Visual acuity, overrefraction, slit-lamp examination, and keratometry
How long should the patient wear the lenses before their follow up check? 6 hours
At the follow up check, what should be examined during the slit-lamp evaluation? lens centration, movement, lens surface, and the lens/corneal relationship
when doing follow-up K Readings, how much change is acceptable? 0.50D
All extended wear contact lenses are designed to be continuously worn for how long? 1 week
In extended wear contacts how often should you take them out to clean and disinfect, and how long should you leave the out? once a week they should be taken out and left out over night
When should the first follow up visit be with an extended wear patient? the following morning with in 2 hours of awakening
what is the typical follow-up schedule of a new extended wear patient? one day, three days, one week, and 1 month
What is the subjective symptom of corneal edema? hazy or foggy vision
What is another name for a keratometer? ophthalmometer
What is rose bengal used for? A red dye used to stain dead epithelial cells
What type of corneal stain has pinpoint breaks in the epithelium? Stippling or punctate staining
What does a 3 and 9 o'clock stain look like? stippling on the outside edges of the cornea at 3 and 9 o'clock
A curved corneal stain in the periphery of the cornea is what type of stain? Arcuate stain
What are the points where the top and bottom eyelids meet? Canthi
What is the bit of skin that holds sweat and sebaceous glads and is located on the medial canthus? Caruncle
What is the average pH of the tear film? 7.4
What is Keratitis Sicca? dry eye syndrome, corneal inflammation due to tear deficiencies
What is Dacryocystitis? inflammation of the lacrimal sac
What is Epiphoria? faulty drainage causing the tears to spill over the lid margin onto the cheek
Where is the lipid layer in the tear film produced? meibomian glands and glands of zeis
What are the accessory glands that secrete the aqueous layer in the tear film? glands of wolfring and krause
Where is the mucin layer in the tear film produced? goblet cells
What is the outer tunic made up of? Sclera and cornea
Lack of oxygen to the cornea is called what? Hypoxia
What does the middle tunic consist of? iris, ciliary body, and choroid
What is aniridia? congenital absence of the iris
What is it called when someone has unequal pupil sizes? Anisocoria
What is rubeosis? neovascularization of the iris
What does the inner tunic of the eye consist of? the retina
what are the layer of the crystalline lens? capsule, cortex, and nucleus
What are the fibers that attach the crystalline lens to the ciliary body? zonules of zinn
in contact lenses, where is the base curve measured? the back surface of the lens
What curve on the lens in used to create a tear reservoir to help facilitate the flushing effect blinking has on the tears under the contact lens? the peripheral curves
The lens diameter should be ______ mm smaller than the horizontal visible iris diameter(HVID) 2mm
what is the formula to convert keratometry readings? 337.5/diopters or 337.5/mm
What is the fitting curve? the back surface of the contact lens
What is the power curve? the front surface of the contact lens
When the cornea has more curve on the vertical meridian than the horizontal, it is called what? with the rule astigmatism
When the cornea has more curve on the horizontal meridian than the vertical meridian, is called what? against the rule astigmatism
A lens that is centered between the top and bottom lids so that the top lid has nothing to do with where the lens is fitted is called what? intrapalpebral fit
An increase in peripheral lens edge thickness to aid in raising a low riding contact lens is called what? myo flange design
An increase or decrease in the anterior edge thickness to aid in lens positioning is called what? lenticular flange
What is the power range of a keratometer? 36.00D-52.00D
What is an extra lens added to an instrument for the purpose of supplementary power? Auxiliary lens
What illumination is it when the light is right beside the [art of the eye being examined? indirect illumination
What illumination is it when the light is behind the part of the eye that is being looked at? retro illumination
What slit lamp illumination is it when you shine a 2-3mm light at the limbus at a 90 degree angle? sclerotic scatter
Why type of stain is an arc shaped corneal abrasion caused by the edge of a contact lens? Arcuate Stain
indentations in the corneal epithelium caused by air bubbles getting between the back of the lens and the front of the cornea is an example of what stain pattern? dimple veiling
What RGP lens has no lenticular carrier and is usually spherical? Single cut lens
What is residual astigmatism? The amount of astigmatism left after subtracting the refractive cylinder and the corneal cylinder
What is a tangent streak RGP? a traditional executive bifocal design
What is another name for scleral contact lenses? Haptic lenses
What is the profile analyzer? a tool used to examine the edge design of a RGP
How do you assess the quality of the peripheral curves? using a shadowgraph
The CPC of a rigid lens was ordered 7.84 mm and was received measuring 7.94 mm. This lens is _______ than ordered. 0.50 flatter
an excellent material for a keratoconus patient would be? Silicone acrylate
What ophthalmic instrument is used to assess the shape of the anterior surface of the cornea? Keratoscope or placido's disk
the normal cornea is in a state of what? deturgesence
Using a 2-3mm beam, directed at the cornea and a ring of light appears around the cornea to observe opacities, is what type of illumination? Sclerotic scatter
Using a 2-3mm beam to see behind the observed area and is used for seeing corneal vascularization, edge design and edema, is what type of illumination? retro illumination
What illumination is best to view neovascularization? Indirect Illumination
Using a small circular beam of light to view flare and cells in the anterior chamber, is what type of illumination? Conical beam
What illumination is accomplished by aligning the microscope along the angle of reflection of the light and is used to detect minute imperfections on the contact lens surface? Specular reflection
A form of direct illumination that uses the narrowest beam to see the layers of the cornea and the check angles, is what type of illumination? optic section
What is the most common form of direct illumination used to evaluate the fit of contact lenses? Parallelpiped Illumination
Created by: Kayla Carpenter