COT Flash Card
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Transcript of COT Flash Card
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7/27/2019 COT Flash Card
1/7
o Visible light lies between what wavelengths (in nanometers)?
o Approximately 400-800 nanometers
o
o The wavelength of light makes a difference in how the eye perceives it. Which
characteristics of visible light is determined by its wavelength?o Color
o
o Which color has the longest wavelength? The shortest?
o The longest: Red 650 nm-750 nm The shortest: Blue 446 nm-500 nm
o
o Polarized lenses block all light rays except those the do what?
o Vibrate in the same direction
o
o What common in-office test uses glasses with polarized lenses?o Stereopsis (Titmus fly)
o
o Because of refraction a prism bends light rays toward the base or the apex of the
prism. In what units is the power of the prism measured?
o Toward the base
o
o The power of a prism to bend light depends on the size of the angle at the apex
of the prism. In what units is the prism measured?
o Prism diopters
o
o What does the formula P=C/D represent?
o This formula explains the relationship between the power of prism and ability to
bend light. P is prism diopters, C is the displacement of the object in centimeters, and D is the
distance between the prism and the virtual image in meters
o
o Two prisms places base -to-base form the basis of what type of lens?
o Convex (plus)
o
o Convex (plus) lenses do what to light rays?o Converge them
o
o Two prisms places the apex-to-apex form the basis of what type of lens?
o Concave (minus)
o
o Concave (minus) lenses do what to light rays?
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o Diverge them
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o Fresnel prisms are usually applied to the front surface or the back of a patient's
eyeglasses?
o Back surface
o
o What is Pretice's rule?
o Its formula to calculate induced prismatic effect caused by spectacle lenses
whose optical centers have been decentered so they are not in line with a patients visual axis
(pupil center). The formula is: Induced prism (in prism diopters)=lens power (in diopters) X Optical
center displacement (in cm)
o
o Find the total amount of prism induced in the following situations: Glasses RX
OD +12.00 sph OS +10.00 sph - Both optical centers are displaced 5 mm temporally (decentered
out)
o OD has 6 prism diopters of Base Out / OS has 5 prism diopters of Base Out /The total is 11 prism diopters of Base Out
o
o Name the variable focusing power of the eye provided by the flexibility of the
crystalline lens.
o Accommodation
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o Clinically, infinity is determined to be at what distance?
o 20 feet (6 meters) and beyond
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o What is the Prince rule used to measure?
o Near point of accommodation, and bifocal and trifocal add power
o
o Explain amplitude of accommodation.
o Its the crystalline lens change (in diopters) from a state of no accommodation to
maximum accommodation
o
o What happens to a person's amplitude of accommodation as they age?
o It decreases
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o The loss of accommodation due to increasing age is called what?
o Presbyopia
o
o What is the focal length (in meters) of a 3 diopter lens?
o P = 1/f (meters), 3 = 1/f (meters), 3f (meters) = 1, f (meters) = 1/3, or 33cm
o
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7/27/2019 COT Flash Card
3/7
o The strongest the power of a plus lens, the (more/less) distance it needs to
focus?
o Less
o
o Snell's law determines what?o Whether the refracted ray will be bent toward the normal or away from it
o
o Index of refraction (IR) compares what?
o Speed of light in a vacuum to the speed of light in a given substance
o What's the IR of water? What is the IR of crown glass?
o Water 1.000; crown glass 1.517
o
o What is axial length?o The length of the eye from the front surface of the central cornea to the macula
o
o Hyperopic eyes often have axial lengths longer or shorter than average?
o Shorter (24mm)
o
o Can myopic eyes use accommodation to being the distance objects into focus?
o No
o
o What is astigmatism?
o A refractive error caused by the nonsperical (cylindrical) surface of the cornea or
lens, or both
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o How is astigmatism corrected?
o With spherocylindrical lenses
o
o "With the rule" astigmatism is corrected by plus cylinders at or near what axis?
o 90 degrees
o
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o "Against to rule" astigmatism is corrected by plus cylinders at or near what axis?
o 180 degrees
o
o Name the clinical procedure performed by ophthalmic personnel for determining
a patients refractive error.o Refractometry
o
o When using a streak retinoscope, if you see "with" motion, this indicates the need
to place what kind of lens power in front of the eye?
o More plus power
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o When using a streak retinoscope, if you see "against" motion, this indicates the
need to place what kind of lens power in front of the eye?
o More minus power
o
o What is the spherical equivalent of the following prescription: +2.00 +1.50 X 090?
o "= +2.75 sphere (half the CYL + SPH)"
o
o Transpose the following eyeglasses Rx into the minus cylinder form: +2.00 +1.25
X 173
o "+3.00 -1.00 X 003"
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o Transpose the following eyeglasses Rx into the minus cylinder form: -2.00 +1.25
X 173o "-0.75 -1.25 X 083
o
o Give 3 examples of clinical use of Keratometry readings.
o (1) detecting the amount and direction of corneal astigmatism, (2) selecting
contact lenses, (3) determining the power of an IOL to be implanted, (4) detecting keratoconus
o
o Give the prescription represented by the following optical crosses:
o a) +3.00 b) "-2.25 +2.25 X 180 or plano -2.25 X 090 c) 1.25 +3.25 X 135 or +2.00
-3.25 X 045"
o
o Abnormal visual acuity in children can be improved to normal with vigorous
training until what age? After that age is becomes difficult to change the visual patterns.
o Age 6; After that age is becomes difficult to improve visual acuity.
o
o What does CSM stand for?
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o Central - indicates that the corneal reflex is the same in both eye; Steady -
means that fixations is not wandering and nystagmus is not present; Maintained - denotes that
fixation is sustained by a given eye through a blink or following of an object.
o
o What test is performed to determine an estimations of misalignment when
looking at corneal light reflexes of both eyes?o Hirschberg test
o
o When prisms are used to equalize position of corneal light reflexes, this test is
called the ________________________________.
o Krimsky test
o
o When the eyes appear misaligned due to epicanthal folds, but no strabismus is
found, this condition is called _______________________.
o Pseudostabismus
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o What test is used to differentiate pseudostrabismus from true starbismus?
o Hirschberg test
o
o What are versions?
o Simultaneous movement of both eyes in the same direction.
o What is duction?
o Movement of one eye only
o
o What is vengeance?
o Simultaneous movement of both eyes in opposite directions, such as
convergence or divergence.
o
o What is phoria?
o A latent ocular deviation made intermittent by disrupting fusion. Deviation occurs
when a cover is placed over an eye; when uncovered, the eye straightens.
o
o What is tropia?o A constant ocular deviation caused by extraocular muscle imbalance.
o
o To measure vertical and/or horizontal phorias or topias at either distance or near,
what device is used?
o Maddox rod, red lens along with the Risley prism, or hand-held prisms
o
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o What is NRC, normal retinal correspondence?
o The images of each eye form or similar (corresponding) parts of the retinas of
each eye, e.g., the fovea's. This results in binocular vision and steropisis.
o
o When the fovea of one eye corresponds to a nonfoveal point in the other eye,
this is called ARC, abnormal or anomalous retinal correspondence, and_______________________ or _________________ occurs.
o Strabismus / suppression
o
o What test is performed to detect the presence of fusion or the suppression of one
eye?
o Worth four-dot test, stereo test (Titmus Fly test), red filter, or amblyoscope
o
o What are the clear, finely striated, non-cylindrical lenses used for evaluating
correspondence in patients with deviations called?
o Bagolini lenseso
o What is amblyopia?
o Lazy eye. Decreased vision of 20/40 or worse in one or both eyes without
detectable anatomic damage in the eye or visual pathways. Uncorrectable by optical means after
the age of six, although many ophthalmologists might try therapy until the age of nine.
o
o What is strabismus?
o Misalignment of eye(s) caused by extraocular muscle imbalance.
o
o What are causes of amblyopia?
o Starbismus, significant refractive error, anisometropia or uncorrected refractive
error, ptosis, cataract, or corneal opacities.
o
o What treatment is used to correct a strabismic amblyopia?
o Patching of the good eye to force the amblyopic eye (lazy eye) to work harder.
o
o When a muscle assists the primary muscle in the same eye to make a particular
movement what is this muscle called?
o Synergist muscleo
o A pair of muscles, one in each eye, work together to achieve a desired version
movement, this pair of muscles is called _________________.
o Yoke muscles
o
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o The __________________ muscle is the prime mover for a desired direction of
gaze.
o Agonist muscle
o
o The voluntary rapid eye movements of both eyes, controlled by the frontal lobes
of the brain, in the same direction to re-fixate is called ___________________.o Saccades
o
o The antagonist muscle of the same eye works directly against the
___________________ muscle.
o Agonist
o
o All of the extraocular muscles, except the inferior oblique, originate at the
________________ ________ ___________________.
o Annulus of Zinn
o
o The medial rectus muscle is innervated by what cranial nerve?
o CNIII (cranial nerve III), also known as Oculomotor cranial nerve.
o
o What is the primary function of the medial rectus?
o Adduction - rotate the eye medially towards the nose.
o
o What muscle, as its primary function, ABDucts the eye?
o Lateral rectus
o
o This muscle is innervated by the abducens nerve (CN VI).
o Lateral rectus
o
o What are the four cyclovertical muscles?
o Superior rectus, inferior rectus, inferior oblique, and superior oblique
o
o What are the 3 actions (in order) of the superior rectus muscle?
o a) primary action - elevation, b) Secondary action - intorsion, c) Tertiary action -
adduction
