SAMPLE TEST Flashcards
(43 cards)
Which of the following medications may affect successful contact lens wear ?
Antihistamines are beneficial when treating allergies and cold symptoms because they dry
out the mucous membranes of the nasal passage. However, this may also lead to dehydration
of the tear film. Antihistamines have also been known to slow down the blink rate and
increase corneal sensitivity.
What is the term for light sensitivity ?
Photophobia refers to a sensitivity (“phobia”) to light (“photo”). Presbyopia is the condition
that results when patients are no longer able to focus on objects at a near point.
Pannus is the invasion of blood vessels onto the cornea. Ptosis is a drooping of the upper
eyelid.
The following is an example of what kind of astigmatism ?K’s 42.50 @ 180/40.50 @ 90
Against-the-rule-astigmatism is present when the keratometer readings are steeper in the horizontal meridian (42.50 @ 180) than in the vertical meridian (40.50 @ 90).
The cornea receives nutrients from what ?
The normal cornea is devoid of blood vessels. 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. The orbicularis occuli is a muscle in the eyelid whose primary .
function is lid closure.
Increased loss of ability of the lens to accommodate is called ?
Presbyopia is the gradual loss of accommodation due to the hardening of the crystalline
lens that takes place as a person ages
Increased loss of ability of the lens to accommodate is called ?
Presbyopia is the gradual loss of accommodation due to the hardening of the crystalline
lens that takes place as a person ages.
Which Instrument can provide stimulation information about the cornea, lids, conjunctiva, lashes, contact lens surface and fit ?
Slit lamp
The radiuscope will measure the base curve of a rigid contact lens. The corneascope and
keratometer will give important information about the surface of the cornea. Only the slit
lamp (or biomicroscope) can provide simultaneous information about the cornea, lids,
conjunctiva, lashes, contact lens surface and fit.
What are the layers of the tear film ?
Lipid, aqueous, mucin
Transpose Rx -4.50 +1.25 x 94
To transpose a prescription from plus to minus cylinder, first add the amount of cylinder
to the sphere power: -4.50 + (+1.25) = -3.25
Then change the sign of the cylinder power from plus to minus: +1.25becomes -1.25
Finally, add or subtract 90 degrees from the cylinder axis: 94 - 90 = 4
Avg pH Value of Tears
Values higher than 7.4 are considered relatively alkaline, whereas values lower than 7.4
are considered relatively acidic.
If the manufacturer’s guidelines suggest
a minimum of 4 hours for disinfection,what would you suggest to the patient?
Patients should always be directed to follow the manufacturer’s guidelines and not try to
cut corners by leaving lenses in any solution for less than the recommended time. While
overnight is longer than recommended and would not pose a problem for most: patients,
they should always be given very specific guidelines for time.
What is the term for the condition in
which there is loss of vision without any
apparent disease to the eye?
Patients are amblyopic when they are not able to attain 20/20 vision with an eye that has
not experienced any disease or trauma. Aniridia is the absence of an iris. Astigmatism
refers to a refractive error in which light rays do not focus in a single point. Ap hakia is the
absence of the crystalline lens.
Which auxiliary trial lens will extend the
keratometer range to approximately
30.00 D?
By placing a -1.00 D lens over the aperture of the keratometer, you can extend the low end
range from 36.00 D to 30.00 D.
Which step should be performed first when taking keratometer measurements? A. Rotate the drum to reflect the cylinder axis B. Adjust the patient so that they are comfortable C. Focus the eyepiece D. Cover the patient's eye that is not being measured
The answer is C
Before the patient is seated in the keratometer, the examiner should focus the eyepiece.
This is particularly important if you are not the only person using the keratome ter during
the day.
The following is an example of what type
of astigmatism?
K’s 44.00 @ 180/44.50 @ 90
Rx -3.00 -2.50 x 180
Lenticular astigmatism is present when there is significantly more astigmatism in the
patient’s refraction (2.50 D) than on their corneal surface (0.50 D). In this case, the
astigmatism is not represented on the cornea and is most likely found in the crystalline
lens.
Ocular signs of aging include:
1) Tear film abnormalities
2) Reduced lid elasticity
3) Lens opacities
4) Loss of accommodation
ALL of them
Transpose the following Rx into minus cylinder form: Rx +1.50 +1.00 x 75 A. +1.50 -1.00 x 75 B. +2.50 -1.00 x 75 C. +2.50 -1.00 x 165 D. +2.50 -1.00 x 175
The answer is C
To transpose a prescription from plus to minus cylinder, first add the amount of cylinder
to the sphere power: + 1.50 + (+1.00) = +2.50
Then change the sign of the cylinder power from plus to minus: +1.00 becomes -1.00
Finally, add or subtract 90 degrees from the cylinder axis: 75 + 90 = 165
The pre-corneal tear film provides:
1) A smooth optical surface
2) Metabolic nutrients to the epithelium
3) Oxygen to the endothelium
4) Limbal hyperemia
The pre-corneal tear film provides a smooth optical surface for the cornea. This is maintained
by the blink mechanism, further providing metabolites (e.g., oxygen) to and from the cornea as well as removing waste products such as CO2 and dead epithelial cells. The
endothelium receives its oxygen from aqueous humor within the anterior chamber. Limbal
hyperemia is redness from engorged blood vessels in the limbal area.
The cornea has five distinct layers. In
order from anterior (front) to posterior
(back) they are:
Epithelium, Bowman’s layer, Stroma,
Descemet’s membrane, Endothelium
The normal cornea is transparent due to the pump action creating proper fluid balance. Which layer of the cornea is most responsible for maintaining this function?
The corneal endothelium provides the pumping mechanism of the cornea to expel fluid
from the tissue and maintain corneal transparency. Bowman’s layer is an acellular layer
which provides strength to the cornea. The epithelium is the outermost layer of the cornea
and only plays a minor role in corneal metabolism. The basal membrane is a basement
membrane which provides an attachment surface for the epithelium to adhere to
Bowman’s layer.
A normal tear break-up time is:
Typically fluorescein will remain on the cornea for 10-12 seconds before it begins to break
up and dry spots appear. Less than seven seconds is considered a short break-up time and
may limit the success of contact lens fitting.
A whitish haze in the peripheral corneal stroma which does not stain and is often seen in the elderly is known as: A. Neovascularization B. Dellen C. Arcus Senilus D. Fuch's Dystrophy
Arcus senilus consists of cholesterol deposits in the corneal periphery and does not affect
contact lens wearing. A dellen is a depressed area of compromised epithelial tissue on the
cornea which stains due to lack of wetting from the pre-corneal tear film. It is generally
found adjacent to an elevated area. Neovascularization is the abnormal growth of new
blood vessels into the cornea. Fuch’s dystrophy is a corneal endothelial dystrophy affecting
the central cornea.
Patients with keratitis sicca are more prone to: A. Secondary infections B. Loss of eyelashes C. Losing their contact lenses D. Steepening corneas
Keratitis sicca is a severe dryness of the cornea. This leaves the cornea at risk, exposing it
to complications related to secondary infections. Loss of eyelashes or contact lenses and
steep corneas are not related to keratitis sicca.
Upon removal of the crystalline lens, the patient is: A. Aphakic B. Myopic C. Hyperopic D. Astigmatic
Aphakia is the absence of the crystalline lens.
