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75 Cards in this Set
- Front
- Back
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Type of medication that may affect successful contact lens wear?
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Antihistamines - they dry out mucus membranes of the nasal passage, which may lead to dehydration of the tear film. May also slow down blink rate and increase corneal sensitivity.
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Photophobia
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Sensitivity to light
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Presbyopia
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Patients are no longer able to focus on objects at a near point.
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Pannus
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Invasion of blood vessels onto the cornea.
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Ptosis
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Drooping of the upper eyelid.
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What type of astigmatism is this: K's 42.50 @ 180 / 40.50 @ 90
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Against the rule astigmatism, present when the keratometer readings are steeper in the horizontal median *42.50 @ 180 than in the vertical meridian *40.50 @ 90
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The cornea receives nutrients from:
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To provide metabolites, the cornea is nourished by diffusion of nutrients and oxygen by the aqueous humor, tears and vascular blood vessels in the limbus.
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Primary function of the orbicularis occuli?
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Lid closure
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Presbyopia
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Gradual loss of accomodation due to the hardening of crystalline lens that takes place as a person ages.
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Radiuscope
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Measures the base curve of a rigid contact lens.
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Corneoscope & Keratometer
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Give important information about the surface of the cornea.
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Slit Lamp (Biomicroscope)
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Provides simultatneous information about the cornea, lids, conjuctiva, lashes, contact lens surface and fit.
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What are the three layers of the pre-corneal tear film?
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Lipid - anterior
Aqueous Mucin Layer - posterior |
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Transpose the following Rx into minus cylinder form:
-4.50 +1.25 x 94 |
-3.25 -1.25 x 4
You get this by taking the first equation (-4.50 +1.25 = -3.25), then change the sign of the +1.25 to -1.25. Finally subtract 90 degrees from the cylinder (94-90 = 4) |
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What is the average ph value of the human tear?
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7.4 - values higher are considered alkaline, values lower are considered acidic.
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If the manufacturers guidelines suggest a mininmum of 4 hours for disinfection, what do you suggest?
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The same as the manufacturer. Always give the patient specific guidelines.
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What is the main supply of oxygen to the corneal epithelium?
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Tear film - oxygen dissolves into tears where it can be utilized by the corneal epithelium.
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Amblyopia
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Loss of vision without any apparent disease to the eye.
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Aniridia
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Absence of an iris
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Astigmatism
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Refractive error in which light rays do not focus in a single point.
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Aphakia
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absence of the crystalline lens.
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Which auxiliary trial lens will extend the keratometer to approximately 30.00 D?
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By placing a -1.00D lens over the aperture of the keratometer you can extend the low end range from 36.00D to 30.00D.
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This step should always be performed first when taking keratometer measurements.
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Focus the eyepiece - important because of other people using the keratometer.
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This is what kind of astigmatism?
K's 44.00 @ 180 / 44.50 @ 90 R's -3.00 -2.50 x 180 |
Lenticular Astigmatism - present when there is significantly more astigmatism in the patients refraction *2.50D than on their corneal surface *0.50D - In this case the astigmatism is not represented in the cornea and most likely found in the crystalline lens.
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Tear film abnormalities
Reduced lid elasticity Lens opacities Loss of accomodation |
All ocular sings of aging.
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Transpose the following into minus cylinder form.
RX +1.50 +1.00 x 75 |
+2.50 -1.00 x 165
(+1.50 +1.00 = 2.50) then change the (+1.00 to -1.00) then take 75+90 = 165. |
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The pre corneal tear film provides
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A smooth optical suface for the cornea and metabolic nutrients to the epithelium.
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What are the corneas five distinct layers in order, from anterior to posterior.
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Epithelium
Bowmans Membrane Stroma Descemets membrane Endothelium |
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The normal cornea is trasnparent due to the pump action creating proper fluid balance. Which layer is most responsible for this?
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Endothelium - provides the pumping mechanism of the cornea to expel fluid from the tissue to maintain transparency.
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Bowmans Membrane
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Accelular layer which provides strenght to the cornea
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Epithelium
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Plays a minor role in corneal metabolism
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Basal Membrane
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Basement membrane provides an attachment serface for the epitelium to adhere to bomwans membrane.
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A normal tear break up time?
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10 - 12 seconds
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What is a whitish haze in the peripheral corneal stroma which does not stain and is often seen in the ederly?
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Arcus Senilus - consists of cholesteral deposits in the corneal periphery and does not affect contact lens wearing.
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Dellen
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Depressed area of compromies epithelial tissue on the cornea which staines due to lack of wtting from the pre-corneal tear film.
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Neovascularization
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Abnormal growth of new blood vessels into the cornea.
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Fuch's dystrophy
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Corneal endothelial dystrophy affecting the central cornea.
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Patients with keratitis sicca are more prone to:
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Secondary infections
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Keratitis sicca
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a severe dryness of the cornea
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Upon removal of the crystalline lens, the patient is?
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Aphakic - absence of the crystalline lens.
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The following RX represents?
OD +2.00 =20/20 OS -3.00 -2.00 x 180 = 20/20 |
Anisometropia - present when the refractive errors of a patients two eyes are so different from one another that retinal images of disparate sizes result. fusions may not occur because of the different sizes.
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The last patient will best achieve stereoposis with which of the following modalities?
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Contact lenses
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Stereoposes
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Depth Perception
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Tom's spectacles with a power of -12.00 +0.50 x 90, sit 10 mm in front of his cornea. The likely soft contact lens prescription for tom would be?
-10.40D, -12.00D, -11.75D or -12.50D |
-10.50 D - in conversion of a perscription from the specactly plane to the corneal plane, additional plus power is needed.
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Keratometer is used to measure?
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Corneal curvature
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Lensometer measures?
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Power
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Diameter guage measures?
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Diameter
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Thickness guage measures?
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Thickness (holy crap thats easy)
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What instrument is used to evaluate corneal irregularity by reflecting concentric circles from teh patients cornea?
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Placido Disk
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Burton Lamp
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evaluates fluorescein patterns in the absence of a slit lamp.
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Con-Ta-Check
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an attachment to the keratometer that enables on to read the base curve in the absence of a radioscope.
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Topogometer
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an attachment to the keratomter and is used to define the corneal apex.
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What is the range of a keratometer?
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36.00 D to 52.00D
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Which auxillary trial lens will extend teh keratometer to approx. 61.00 D?
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+ 1.25 D lens is used to range above 52.00D
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What is a chalzion?
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Inflammation of a meibormian gland and is not related to dryness.
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Can people in most occupations wear contact lenses?
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Yes, even arc welders can wear them.
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Transient keratometric mire distortion is usually do to what?
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Pre-ocular tear film - this only results in transitory mire distortion which can be cleared up if you ask a patient to blink.
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In against-the-rule astigmatism the steepest corneal meridian is?
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at or near 180 degrees. in this astigmatism the cornea has a vertical ellipsoidal shape. This puts the long flast meridian at 90 degrees and the short steep meridian at 180 degrees.
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Irregular mires on a keratometer may be indicative of?
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Dry eyes or excessive mucoid secretions
Contact lens induced corneal warpage Keratoconus |
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In an alignment lid attachment RGP fit, the flourescein pattern should show:
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A thin even layer of flourescein and less than 180 degrees of bearing in the mid-periphery.
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In an RGP wearer, an arcuate stain on the cornea may be due to:
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Poorly blended secondary curves.
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In a Shirmer I Test:
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A patient with an unanesthetized eye and normal tear output should wet at least 15 mm of the filter paper in 5 minutes.
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In a Shirmer II Test:
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Break up time must be at least 10 seconds if a patient is to be a successful contact lens wearer.
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Rose bengal testing:
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will cause a dense, confluent staining with a uniformly intense red color in a pathologically dry eye and a discrete punctate conjuctival stain in a marginally dry eye.
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When evaluating tear film break-up-time:
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A break up time of less than 10 seconds may preclude success with contact lenses.
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Break up Testing (BUT)
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is done by instilling flourescein, having the patient blink once to spread the flourescein across the cornea and timing the interval between the blink and the development of the first dry spot (tear break up) on the cornea. Generally a BUT greater than 10 seconds is needed for successful contact lens wear.
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The preservation in contact lens solution:
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is formulated to keep microorganisms from multiplying in a bottle of contact lens solutions after it has been opened.
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A patient wearing a high horizontal prismatic correction for a motility problem:
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May experience diplopia when fit with contact lenses and may need plano glasses with prism ground into them to wear over the contacts.
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A pre-presbyopic myopic patient who is still able to read with single vision glasses may find that:
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They are unable to see fine print when fit with contact lenses. They may find that their near vision is still adequate with glasses however.
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Amy's +8.50 spectacles sit 12 mm from the cornea. The power of a soft contact lens for Amy, properly vertexed, would be:
+8.00 D, +8.50 D, +9.50 D or +11.00 D |
+9.50 - Vertex distance must be taken into account when spectacle power is +/- 4.00 D. In the conersion of a prescription from spectacle plane to corneal plan, additional plus power is needed. Thus, less minus power is requred for a high myope's contact lens compaered to their spectacle prescription.
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Which of the following would work best for the patient's visual needs, given the following info:
K's 44.00 @ 180 / 45.25 @ 90 R's -3.00 +0.25 x 90 |
The patients refractive astigmatism is 0.25 diopers, which is essentially a spherical correction. A soft spherical lens will correct this although corneal astigmatism is present.
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Which of the following set of lens specifications would best simulate an intrapalpebral RGP fitting given the following information:
K's 42.00 @ 180 / 43.00 @ 90 R's -2.00 -1.00 x 180 Upper lid positions 2 mm above the superiou limbus A. 42.50 -2.50 8.5 B. 42.00 -2.00 9.5 C. 41.50 -1.50 8.5 D. 41.50 -1.50 9.5 |
42.50 -2.50 8.50
An intrapalpebral fit is a small diameter, steep fitting lens designed to center between the upper and lower eyelids. All other answers are either large diameter or flat fitting lenses. |
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Which contact lens would best correct this patients visual needs, given the following information:
K's 46.00 @ 180 / 45.50 @ 90 R's - 3.00 -1.50 x 90 A. A soft spherical lens B. A soft toric lens |
A soft toric lens. A soft spherical lens would not correct the lenticular astigmatism.
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Which of the following material components has the highest gas permeability?
Flourine, PMMA, Butyrate or Silicone? |
Silicione is 100% oxygen permeable and is responsible for increasing the oxygen permeability of many RGP materials.
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When documenting in a patients chart on a new-fitting recheck, what is not necessary?
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Sister's lens type that has caused no problem. It may be interesting, but the type of lens that this sister is wearing is not critical info.
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