Term
Who was the Italian Renaissance painter who described how a glass lens could change the optical power of the cornea? |
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Definition
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Term
In 1888 what two individuals independently tried to correct vision errors by placing glass lenses on the cornea? |
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Definition
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Term
Who was the first scientist to develop a soft (hydrogel) contact lens? |
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Definition
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Term
Who created the first all-plastic corneal lens made of PMMA? |
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Definition
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Term
In 1986 what substance was added to Rigid Gas Permeable contact lenses to make them more wetable? |
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Definition
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Term
If a yound patient is not wearing spectacles or contact lenses, and thier distance vision is blurry, but their near vision is clear, what is their refractive state? |
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Definition
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Term
What type of contact lens is designed specifically to correct astigmatism? |
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Definition
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Term
What lens material is stable, has good machining properties, but allows little to no oxygen through the cornea? |
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Definition
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Term
What lens material (when made available as a spherical contact lens) is comfortable, but does not compensate well for corneal astigmatism. |
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Definition
HEMA- Hydroxyethyl Methacrylate |
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Term
What type of contact lens material was recently FDA approved for 30-day continous wear? |
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Definition
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Term
What are the three most important parameters of an RGP lens? |
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Definition
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Term
Consider an RGP with a base curve, and a peripheral curve. What is another name for the base curve diameter? |
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Definition
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Term
In an RGP contact lens, when the junction between two curves is too sharp, we smooth it out during lens modification. This smoother junction is called? |
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Definition
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Term
The keratometer is an optical instrument designed to measure what? |
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Definition
The radius of curvature of the cornea |
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Term
The keratometer does not measure? |
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Definition
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Term
In keratometery, how much of the patients cornea is being examined? |
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Definition
3-4 mm of the central cornea |
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Term
List four reasons why a clinician would want to use a keratometer. |
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Definition
- Contact Lens Fitting
- Corneal cylinder can be used to determine the spectacle RX.
- To help determine if the patient has kerataconus
- Distorted mires could indicate pathology
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Term
What instrument is more accurate than the keratometer when measuring corneal curvature? |
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Definition
Computerized corneal topographer |
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Term
Which topographical map takes peripheral corneal flattening into consideration? |
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Definition
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Term
Why would we consider fitting a keratoconic patient with an RGP lens? |
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Definition
The vision is usually superior to spectacles |
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Term
Which computerized corneal topographical map predicts flourescein patterns when fitting RGP's? |
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Definition
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Term
Name four reasons why a clinician would use a computerized corneal topographer over a keratometer. |
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Definition
- Pre and post refractive surgery measurements
- More accurate than keratometer for fitting RGP's
- Helps when fitting keratoconics with RGP's
- Easier to assess cornea with irregular astigmatism due to disease or trauma
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Term
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Definition
The flattest principal meridian with the smallest dioptric value, also referred to as "on-K". |
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Term
What are the three most important instruments used to fit both RGP and soft contact lenses? |
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Definition
- Biomicroscope
- Phoropter
- Keratometer
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Term
Whta type of glands are embedded in the tarsal plate of the eyelid? |
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Definition
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Term
The glands of Krause and Wolfring are what type of eyelid glands? |
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Definition
Accessory Lacrimal Glands |
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Term
List the six important functions of the tear film? |
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Definition
- Keeps the eye moist and lubricated
- Traps debris and washes it away
- Primary sourceof O2
- Smooth refractive surface
- Contains antibacterial substances-lysosomes
- Helps to maintain corneal hydration
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Term
Name the three layers of the tear film and the structures responsible for the production of each, starting with the outermost layer. |
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Definition
- Lipid- Meibomian Glands
- Aqueous - Main lacrimal gland and accessory lacrimal galnds Krause & Wolfring
- Mucin - Goblet Cells
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Term
Name the five Corneal layers starting with the outermost layer. |
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Definition
- Epithelium
- Bowman's layer
- Stroma - lamellae
- Descemet's membrane
- Endothelium
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Term
The corneal epithelium is made up of what three type of cells? |
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Definition
- Squamous cells
- Wing cells
- Basal layer of columnar cells
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Term
Name two important functions of the cornea. |
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Definition
- Refraction of light
- Transmissions of light
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Term
Name three ways the cornea may receive oxygen. |
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Definition
- Diffusion from aqueous humor
- Conjunctival and episcleral capillaries located in limbus
- Atmospheric O2 diffused through the tear film
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Term
Lamellae are found in which corneal layer? |
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Definition
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Term
What are the two types of a biomicroscope? |
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Definition
- Dissecting microscope
- Illumination system
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Term
Name the three reasons to use a biomicroscope. |
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Definition
- Observation of normal ocular sturctures
- Observation of abnormal ocular structures
- Contact lens fitting
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Term
Name five types of illumination used while performing biomicroscopy. |
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Definition
- Direct
- Diffused
- Indirect
- Retro
- Sclerotic Scatter
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Term
Name four types of direct illumination |
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Definition
- Parallelpiped
- Optic section
- Specular reflection
- Conical beam
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Term
What is the most common form of direct illumination? |
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Definition
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Term
A V-channel Gauge is used to measure what parameter of an RGP contact lens? |
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Definition
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Term
A hand magnifier is used to measure what parameters of an RGP contact lens? |
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Definition
Total diameter and/or Optic zone |
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Term
A Radiuscope is used to give an accurate measurement of what RGP contact lens parameter? |
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Definition
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Term
What would be the best instrument to use to measure the optic zone diameter of an RGP contact lens? |
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Definition
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Term
What instrument is often used in the clinic to measure the base curve of an RGP contact lens? |
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Definition
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Term
What instrument is often used in the clinic to measure the power of an RGP contact lens? |
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Definition
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Term
What instrument would you use to verify the center thickness of an RGP lens? |
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Definition
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Term
When using a Radiuscope to determine an accurate base curve radius of an RGP contact lens, it is important that the concave surface of the lens is what? |
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Definition
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Term
You would use a lensometer to measure which RGP parameter? |
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Definition
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Term
When measuring the base curve of an RGP lens with a Radiuscope, what is required in order to get a proper reading? |
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Definition
That the concave surface of the lens is dry |
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Term
What are the three important areas during the preliminary evaluation case history? |
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Definition
- Reasons for CL wear
- Medical History
- CL history
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Term
Why are we interested in the patient's medication? |
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Definition
Many types of medications can cause dry eye |
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Term
Name two ways to obtain refractive data. |
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Definition
- Corneal Topography
- Refraction
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Term
What three areas are examined during Biomicroscopy? |
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Definition
- Externals
- Conjunctiva
- Cornea
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Term
What prismatic correction can be achieved with some contact lenses? |
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Definition
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Term
What three anatomic measurements are taken during the preliminary evaluation? |
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Definition
- Corneal diameter
- Pupil diameter
- Palpebral aperture height
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Term
What is needed to perform a Schirmer Tear Test? |
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Definition
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Term
What is needed to perform a Phenol Red Test? |
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Definition
70 mm cotton thread soaked in phenol red dye |
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Term
What tear film test is performed using flourescein dye, a cobalt blue filter and the biomicroscope? |
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Definition
Tear Break Up time (TBUT) |
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Term
What is the three point touch of a contact lens? |
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Definition
Contact lens must be touching - Upper Sclera
- Cornea
- Lower Sclera
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Term
What are the four criteria that must be met when evaluating contact lens fit. |
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Definition
- Adequate movement
- Stable Vision
- Good Centration
- Undistorted Keratometer mires
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Term
Name three methods of contact lens manufacturing |
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Definition
- Spin Casting
- Lathe Cutting
- Cast Molding
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Term
A contact lens can get lost behind the eye True or False |
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Definition
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Term
Only patients between the ages of 18 and 35 can effectively wear contact lenses. True or False |
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Definition
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Term
Contact Lenses are considered Medical devices True or False |
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Definition
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Term
What are the two broad catergories of contact lenses? |
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Definition
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Term
What are the two categories of Rigid contact lenses? |
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Definition
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Term
PMMA allows little to no oxygen to reach the cornea True or False |
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Definition
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Term
RGP's are more comforatble to wear than soft lenses True or False |
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Definition
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Term
Soft lenses are hydrophobic True or False |
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Definition
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Term
Soft lenses have a larger diameter than RGP's True or False |
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Definition
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Term
Hypoxia causes corneal edema True or False |
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Definition
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Term
The amount of oxygen passing through the CL is determined by what two factors? |
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Definition
- Lens thickness
- Lens material
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Term
The Dk value of a soft lens is dependant on the water content of the lens True or False |
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Definition
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Term
The thicker the CL, the greater the oxygen transmissibility True or False |
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Definition
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Term
Low water content soft lenses have greater resistance to deposits True or false |
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Definition
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Term
Non-ionic soft lens materials easily attract lens deposits True or False |
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Definition
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Term
The spin casting method limits the ability to control the base curve True or False |
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Definition
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Term
Lathe cutting can only produce RGP's True or False |
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Definition
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Term
Cast molding is simple and reproducible True or False |
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Definition
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Term
What are three advantages to fitting spherical RGP's empirically? |
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Definition
- Eliminates fitting visit
- "Used" diagnostic lens is avoided
- The lenses manufactured at a lab may be just as effective as the best fitting diagnostic lens
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Term
What are the four advantages to fitting spherical RGP's with a diagnostic lens set? |
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Definition
- Fewer re-orders (an optimum lens-to-cornea relationship has already been achieved)
- Practitioner confidence in the fit
- Patient has a chance to experience how an RGP will feel on the first visit
- Ability to evaluate patient's vision on first visit
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Term
What are the three advantages to having hundreds of spherical RGP's in stock? |
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Definition
- Convenience to patient (Patients receive replacement lens without delay)
- You can fit directly from stock
- Lens parameter changes can be made without delay
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Term
What role does Sodium Fluorescein play when fitting spherical RGP's? |
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Definition
It is invaluable for assesing the lens-to-cornea fitting realtionship |
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Term
What two instruments are used to observe the Sodium Fluorescein pattern? |
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Definition
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Term
What would you expect to see if there was apical clearance? |
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Definition
Even pooling of fluorescein in the center of lens |
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Term
What occurs during Apical bearing? |
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Definition
Direct contact between the lens and the cornea |
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Term
What refractive condition could account for a dumbell pattern? |
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Definition
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Term
Would we always fit "on-K" for a patient with a spherical cornea? |
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Definition
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Term
Why not fit a spherical RGP on a high astigmat? |
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Definition
Increased 3 and 9 o'clock injection, poor lens positioning, visual complaints, corneal curvature changes, failure to correct residual astigmatism. |
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Term
Name the seven types of astigmatism |
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Definition
- With the Rule
- Against the Rule
- Irregular
- Internal
- Residual
- Refractive
- Oblique
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Term
In which form of astigmatism is the horizontal meridian the least curved (flattest) and the vertical meridian the most curved (steepest)? |
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Definition
With the Rule Astigmatism |
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Term
In which form of astigmatism is the horizontal meridian the most curved (steepest) and the vertical meridian the least curved (flattest) ? |
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Definition
Against the Rule Astigmatism |
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Term
What are the three common reasons for irregular astigmatism? |
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Definition
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Term
What two factors can cause internal astigmatism? |
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Definition
- The toricity of the back surface of the cornea
- The tilt of the crystalline lens with respect to the optic axis of the cornea
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Term
What is another term for internal astigmatism? |
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Definition
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Term
What is another term for refractive astigmatism? |
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Definition
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Term
What is the astigmatism that is still present after a contact lens has been placed on the eye? |
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Definition
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Term
Name three types of toric RGP's. |
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Definition
- Front surface Toric
- Back surface toric
- Bitoric
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Term
What type of RGP lens is used when there is small amount of corneal astigmatism but a large amount of total astigmatism? |
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Definition
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Term
What type of RGP is used when the refractive astigmatism is approximately 40% greater than the corneal astigmatism? |
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Definition
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Term
What type of RGP is used when there is a significant amount of corneal Astigmatism ( more than 3.00D)? |
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Definition
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Term
What is the name of the bitoric lens guide? |
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Definition
The Mandell-Moore Bitoric Lens Guide |
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Term
What are the three most common modification procedures? |
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Definition
- Edge and Surface Polishing
- Repowering
- Peripheral curve blending or flattening
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Term
What four types of tools are needed to modify an RGP? |
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Definition
- Box modification unit
- Suction cup
- Sponge tools
- Radius tools
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Term
What type of polish can NOT be used and why? |
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Definition
Silvo, because it is ammonia based, so it will ruin the RGP. |
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Term
Soft hydrophilic lenses are also known as? |
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Definition
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Term
What are the six main classifications of hydrogel lenses? |
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Definition
- Daily wear/ flexible
- Extended Wear
- Planned Replacement/Disposable
- Tints
- Torics
- Bifocals
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Term
What are the three main classifications of tinted hydrogel lenses? |
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Definition
- Visibility
- Enhancing
- Opaque
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Term
What water content is best for patients with dry eye? |
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Definition
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Term
What five factors contraindicate hydrogel lens wear? |
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Definition
- Irregular corneas ( keratoconus,ocular trauma)
- Radial keratotomy
- Chronic allergies
- Chronic antihistamine use
- Giant Papillary Conjunctivitis (GPC)
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Term
What is a standard rule-of-thumb for fitting hydrogels? |
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Definition
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Term
What might you observe while using the biomicroscope if the lens is too tight? |
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Definition
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