Contact lens Book Questions Flashcards
The individual awarded the first patent for a corneal lens made of PMMA was
A. Da Vinci
B. Tuohy
C. Fick
D.Soper
Tuohy
Polycon I, the first salicylate lens, was developed by
Seidner
The biggest disadvantage of PMMA as a contact lens material is its lack of…
Gas permeability
The FDA has been involved in the approval of new contact lens materials since the year
1968
Which layer of the cornea makes up 10% of the structure’s total thickness:
epithelium
The vertical measurement of the palpebral fissure for an average eye is
10mm
The eyelid muscle responsible for closure of the lids is
orbicularis oculi
The anterior cornea’s main source of oxygen
the atmosphere
a dense opacity of the cornea is called a:
leukoma
The goblet cells that secrete mucous into the tear film are located in which structure
tarsal plate of the eyeid
The transition zone between the bulbar conjunctiva and the palpebral conjunctiva is called
fornix
the middle layer of the three main layers of the globe is mostly responsible for
nutrition
pupillary constriction is called
miosis
the bacteriocidal ingredient found in the precorneal tear film is
lysozyme
Number of extrinsic muscles attached to eye:
six
Fovea centralis of the retina contains
only cones
the bony orbit of the eye is shaped most like a…
Pyramid
The structure that can adjust its focus for various object positions is the
crystalline lens
The term that is used to describe both eyes moving in the same direction, as when they both look left or both look right is
version
the condition where one eye is turned
strabismus
The most refractive optical component of the eye
The Cornea
The main function of the eye’s outer layer
protection
An opacity of the crystalline lens
cataract
loss of vision caused by excessive intraocular pressure is
glaucoma
which of the following structures would belong to the adnexa oculi
tarsal plate
the corneal layer that consists of a single layer of hexagonal cells is the
endothelium
the transitional area that joins the cornea and the sclera is known as the
limbus
the levator superioris muscles
raises the upper lid
swelling of the corneal tissue, or any, is called
edema
inflammation of the mucous membrane that lines the inside of the eyelids and covers the anterior globe except for the cornea is called
conjunctivitis
the anterior ciliary arteries terminate at the
limbus
aqueous humor is secreted by the
ciliary body
all the colors we perceive are produced by the different photopigments found in the retinal cones
3
through strong aphakic spectacles, a patient will see an object
33%
rays if light striking a spectacle lens at its edge create … or distortion
aberration
… is a moderate to high refractive difference in the powers of the two eyes
anisometropia
through spectacles, the astigmatic patient with “against-the-rule” astigmatism will view a square as follows
the square will appear slightly elongated in the vertical meridian
the visual error caused by a cylindrical crystalline lens is known as … astigmatism
lenticular
The practitioner should suspect … astigmatism if there is a difference between the amount of cylinder found by keratometry readings and the amount of cylinder found by refractometry
internal
When myopic patients view an object at near through their spectacles, the prism created through the spectacles is
base-in
a … person must accommodate more when viewing near objects through their contact lenses vs spectacles
myopic
… results when the cornea has been damaged by trauma, inflammation or scar tissue
irregular astigmatisn
objects in the field of vision of a high myope are … when spectacles are worn
minified
… is a developmental anomaly of the cornea that results in irregular myopic astigmatism
keratoconus
when decompensation of the .. occurs, aqueous humor leaks into the anterior layers of the cornea forming bullae
conjunctiva
In the latter stages of keratoconus, the following may be observed
Munson’s sign
distorted mires
corneal opacities
Fleischer’s ring
Which of the following conditions is a contraindication to contact lens wear
serve blepharitis
… lenses are used on patients with recurrent epithelial erosions
bandage
which of the following patients will experience the most image magnificaton
hyperope wearing spectacles
fitting a rigid contact lens steeper than the flattest corneal meridian will introduce … power into the lacrimal
plus sphere
The preferred method of vision correction in keratoconus is
rigid contact lenses
the normal blink rate is approximately … times per minute
12
for patients with a moderate amount of corneal astigmatism (between one and two diopters), which lens type will provide the crispest, most stable vision
rigid spherical
usually causes photophobia, itching, lacrimation, and burning
respiratory allergies
predisposes the eye to drying due to proptosis
thyroid disease
causes changes in the fluid balance of the body
lanoxin
is a systemic drug used in the treatment of acne
Accutane
may cause blurred vision due to its direct action on accommodation
donnatal
The keratometer is patented and trademarked by
reichert
As light waves travel away from a source they become gradually
flatter
Optical infinity is considered
20
Point at which light rays converge is called a
focus
The term to describe the amount of curvature of a light wave is
vergence
the unit of measurement for vergence is
diopter
a light wave that has traveled 50cm from a point source will have a vergence of
+2.00
D=1/d
D=1/0.5mm
Chapter 4
When classic keratometry is performed by having the patient sight on the mirrored image of their eye, alignment of what is accomplished?
The optical axis with the visual axis
An early investigator that studied the curvature of the cornea was ____________________
Placido
Helmholtz
Javal
The doubling device of the keratometer is necessary due to__________________
fine tremor of the eye.
The index of refraction used to calibrate the keratometer is __________
1.3375
The size of the mire (target) on the front of the keratometer is____________
64.0mm
The distance from the front of the keratometer to the front of the cornea when the instrument is in focus is ____________
75.0mm
The eyepiece of the keratometer should be focused _____________.
daily
The keratometer derives its measurement of a meridian from how many points on the cornea?
2
The range of curvatures the keratometer can measure without auxiliary lenses is _____________
36.00D to 52.00D
The chord length of the mire measured by the keratometer without auxiliary lenses is ____________
3.8mm to 26mm
The keratometer eyepiece if not properly focused can cause______________
errors in correctly reading curvature
In addition to measuring the cornea, the keratometer can be used to________________________
check the curvature of a contact lens
Steeper curvatures than normally readable with the keratometer can be taken by adding to the front of the instrument a _______________
Plus (+) 1.25 trial lens
If the whole mire is reflected from the apex _______________
the reading will be too flat
When a part of the mire is reflected from the transitional zone ___________
an inaccurate reading is taken
Errors in keratometry occur _____________
in keratoconus and irregular astigmatism
When the keratometer is properly aligned in front of an eye, the patient will see ___________________
a green light
The axis of corneal astigmatism when taking a “K” reading______________
is the first thing to align
The amount of corneal astigmatism
is the difference between the reading on the horizontal and vertical drums
When the keratometer is out of focus on the cornea ________________________
the lower right mire is doubled
When measuring the horizontal meridian with the keratometer _____________________
the plus mires are superimposed
Another name for the slit lamp is the _____
A) biomicroscope
B) phoropter
C) optic spherometer
D) radius gauge
A) biomicroscope
The historical development of the slit lamp dates back to
A) 1801
B) 1891
C) 1931
D) 1951
B) 1891
A contact lens fitter uses the slit lamp to view all of the following, EXCEPT
A) the fundus
B) corneal scars
C) corneal neovascularization
D) the conjuctiva
A) the fundus
The slit lamp is used in the evaluation of which fitting characteristic(s) of soft lenses?
A) Centration
B) Movement
C) Corneal coverage
D) All of the above
D) All of the above
The two main parts of the biomicroscope are the
A) microscope and chin rest
B) microscope and light source
C) eye piece and power drum
D) light source and joystick
B) microscope and light source
Which magnification would be appropriate for performing a general survey of the eye at the beginning of a slit lamp exam?
A) 6x
B) 15x
C) 25x
D) 40x
A) 6x
What angle will the beam and microscope form during most illumination procedures?
A) 25*
B) 45*
C) 60*
D) 90*
B) 45*
Which slit lamp illumination can be used without the aid of the microscope?
A) Specular reflection
B) Sclerotic scatter
C) Diffuse
D) Retro
C) Diffuse
Which slit lamp illumination is performed with the microscope placed precisely along the angle of the reflected light from the eye?
A) Specular reflection
B) Sclerotic scatter
C) Optic section
D) Diffuse
A) Specular reflection
When diffuse illumination is used in conjunction with fluorescein, what filter should be employed?
A) Blue (ultraviolet light)
B) Red-free (green light)
C) Diffuse
D) No filter (white light)
A) Blue (ultraviolet light)
When an optic section is used in conjunction with fluorescein, what filter should be employed?
A) Blue (ultraviolet light)
B) Red-free (green light)
C) Diffuse
D) No filter (white light)
D) No filter (white light)
A spherical RGP lens fit on K shows fluorescein pooling under the superior and inferior portions of the contact lens, and a dark band of minimal fluorescein horizontally. What kind of astigmatism does this pattern represent?
A) With-the-rule
B) Against-the-rule
C) Residual
D) Oblique
A) With-the-rule
A back toric rigid contact lens fit on K to conform to each corneal meridian will show a fluorescein pattern that is
A) concentrated under the center of the lens
B) concentrated under the edge of the lens
C) evenly distributed
D) vertically oriented
C) evenly distributed
The most useful slit lamp illumination to view gross cornea edema from rigid lens wear is
A) retro
B) direct
C) indirect
D) sclerotic scatter
D) sclerotic scatter
Which of the following is the most likely cause of 3 and 9 o’clock staining?
A) Inadequate blinking
B) Base curve too flat
C) Dk of lens material too low
D) Base curve too steep
A) inadequate blinking
An arc stain seen on the cornea under the peripheral or intermediate portion of a contact lens means that
A) 1, 2 1: bevels are too sharp
B) 1, 3 2: lens needs to be blended
C) 2, 3 3: base curve is too flat
D) 3, 4 4: lens is too large
A) 1, 2 1: bevels are too sharp
What filter is used to improve detection of corneal vascularity?
A) White
B) Yellow
C) Blue
D) Green
D) Green
The slit lamp illumination that gives an overall assessment of the contact lens fit, but no fine detail, is
A) direct
B) diffuse
C) retro
D) sclerotic scatter
B) Diffuse
What color filter enhances the fluorescein pattern behind a rigid lens containing a UV blocker?
A) Grey
B) Green
C) Red
D) Yellow
D) Yellow
Tear break-up time (BUT) is verified with what slit lamp illumination?
A) Indirect
B) Direct
C) Scatter
D) Retro
B) Direct
Which of the following is an abnormal tear break-up time?
A) 5 sec
B) 15 sec
C) 20 sec
D) 30 sec
A) 5 sec
The green filter is used in conjunction with which slit lamp illumination?
A) Specular reflection
B) Conical beam
C) Indirect
D) Optic section
C) Indirect
The slit lamp illumination that shows the entire contact lens, movement, and centration is
A) ratio
B) direct
C) indirect
D) diffuse
D) Diffuse
The slit lamp illumination where a narrow beam of light bisects the corneoscleral juncture is
A) oscillatory
B) indirect retro
C) sclerotic scatter
D) transverse axial
C) sclerotic scatter
Staining at the inferior portion of the cornea of a soft lens wearer is usually caused by
A) improper lens removal
B) a loose lens
C) a tight lens
D) a lens that is too large
A) improper lens removal
Under slit lamp evaluation with fluorescein, corneal area that appear dark and do not hold stain during blinks are most likely
A) dry spots
B) verrucae
C) punctates
D) infiltrates
A) dry spots
With a rigid lens in place, a fluorescein pattern shows a narrow band of dark vertically, and pooling horizontally. This is indicative of
A) a spherical base curve on a spherical cornea
B) a spherical base curve on a with-the-rule cornea
C) a spherical base curve on an against-the-rule toric cornea
D) a toric base curve on a toric cornea
C) a spherical base curve on an against-the-rule toric cornea
A rigid lens showing apical touch indicates a
A) flat fit
B) steep fit
C) large fit
D) small fit
A) flat fit
A rigid lens showing apical pooling indicates a
A) flat fit
B) steep fit
C) large fit
D) small fit
B) Steep fit
An hour glass fluorescein patten with an RGP lens fit on K indicates
A) a steep fit
B) a flat fit
C) with the rule astigmatism
D) against the rule astigmatism
C) with the rule astigmatism
For most illuminations the angle between the beam and the scope is about
A) 30 degrees
B) 45 degrees
C) 90 degrees
D) 75 degrees
B) 45 degrees
To view corneal neovascularity, what slit-lamp illumination is the best one to use?
A) Direct
B) Indirect
C) Retro
D) Diffuse
B) Indirect
The slit-lamp beam is placed behind the area being studied with what illumination?
A) Retro
B) Indirect
C) Sclerotic Scatter
D) Diffuse
A) Retro
The rigid contact lens material used widely in the 1950s, ’60s and ’70s was:
a) silicone acrylate
b) polymethylmethacrylate
c) cellulose acetate butyrate
d) none of the above
b) polymethylmethacrylate
A lens fit with a base curve steeper than the flattest K with a diameter of 8.5mm would follow which fitting philosophy?
a) corneal alignment b) 3-point touch
c) apical clearance d) none of the above
c) apical clearance
A typical optical zone diameter of a corneal alignment fit would be:
a) 6.5mm b) 7.0mm
c) 7.5mm d) 8.0mm
d) 8.0mm
A rigid lens which flexes upon the eye would be best corrected by going:
a) steeper b) steeper and thicker
c) flatter d) flatter and thicker
d) flatter and thicker
A patient with an upper lid that does not cover any portion of the superior portion of the cornea would be best fit:
a) steeper than K with a small diameter
b) flatter than K with a large diameter
c) on K with an 8.8mm diameter
d) none of the above
a) steeper than K with a small diameter
A -10.00D Rx for a spectacle correction would most likely need a contact lens with a power of:
a) -8.00D b) -9.25D c) -10.50D d) -11.75D
b) -9.25D CAP closer add plus
A patient fit with a base curve of 43.00D and a power of -3.00D and then refit with a base curve of 43.50D would require a new power of:
a) -2.50D c) -3.50D b) -2.75D d) -4.00D
c) -3.50D SAM steeper add minus
A patient with a corneal toricity of 4.50 diopters would be best suited with a base curve that is:
a) 1.00 diopter steeper than K
b) 1.50 diopter steeper than K
c) toric
d) none of the above
c) toric
A patient with a base curve of 42.75D, power of -3.00D, if refit with a lens of base curve of 43.50D, would then require a power of:
a) -2.50D c) -3.75D b) -3.50D d) none of the above
c) -3.75D SAM steeper add minus
When fitting rigid lenses, residual astigmatism is most often caused by:
a) high refractive cylinder
b) a toric contact lens
c) corneal cylinder against-the-rule
d) a difference between refractive and corneal cylinder
d) a difference between refractive and corneal cylinder
When using original K readings to refit a former PMMA wearer with gas permeable lenses, it is best to refit:
a) immediately
b) after seven days of no contact lens wear
c) after one month of no contact lens wear
d) none of the above
a) immediately
A patient fit 0.50D flatter than K with a contact lens power of -1.00D would most likely have a spherical component of ___ in their spectacle Rx, when in minus cylinder form.
a) -0.50D b) -1.50D c) -2.00D d) none of the above
a) -0.50D FAP flatter add plus
To achieve apical clearance with a rigid gas permeable lens of 8.5mm diameter, fit on a cornea of average size, the base curve should be:
a) on K b) steeper than K
c) flatter than K d) none of the above
b) steeper than K
A patient with an Rx of +3.00 +0.50 x90 fit 0.50D flatter than K would require a power of:
a) +3.00D b) +3.50D c) +4.00D d) none of the above
c) +4.00D FAP flatter add plus
Which of the following terms is associated with the corneal alignment fitting philosophy?
a) central pooling b) intrapalpebral fit
c) upper lid attachment d) 3 point touch
c) upper lid attachment
A patient with an Rx of +2.00 -1.00 x90 and K readings of 44.00 @180/43.00 @90 reveals residual astigmatism of plano -2.00 x 180. A possible explanation for this is:
a) normal residual astigmatism
b) a steeply fitted contact lens
c) a warped contact lens
d) none of the above
b) a steeply fitted contact lens
A patient wearing a 43.00D base curve, 9.0mm diameter, 7.0mm optical zone diameter requires a change to a 9.5mm diameter with a 7.5mm optical zone diameter. To keep the base curve corneal bearing relationship the same, the new base curve would need to be:
a) 42.50D b) 42.75D c) 43.50D d) 43.75D
a) 42.50D
An Rx of -2.00 -1.50 x180 and K readings of 43.00 @180/46.00 @90 would have a calculated residual astigmatism of:
a) +1.50 x180 b) +2.00 x90
c) +1.50 x90 d) + 1.00 x180
a) +1.50 x180
-1.50 - (-3.00)
The optical zone diameter of a rigid contact lens is generally:
a) 3.0mm smaller than the total diameter
b) 3.5mm smaller than the total diameter
c) 4.2mm smaller than the total diameter
d) none of the above
d) none of the above - The OZ is generally 1.0mm to 1.5mm smaller
Any ophthalmic lens moved closer to the eye becomes effectively:
a) flatter b) steeper c) more plus d) more minus
More minus
The apical clearance fitting philosophy requires a lens that positions:
a) centrally, with upper lid attachment
b) centrally and intrapalpebrally
c) superiorly, with upper lid attachment
d) superiorly and intrapalpebrally
Centrally and intrapalpebrally
A diagnostic lens with a base curve of 7.67mm and an optical zone diameter of 7.6mm fits too tight. Which of the following changes will loosen the fit the most?
a) 7.76mm, 8.0mm b) 7.69mm, 7.8mm
c) 7.63mm, 7.6mm d) 7.71mm, 7.3mm
b) 7.69mm, 7.8mm Higher the mm, flatter the curve;
lower the mm, steeper the curve
Rigid gas permeable lens edge thickness should be between ___mm and ___ mm.
0.08-0.12
Which of the following is NOT an advantage of rigid gas permeable lenses over soft lenses?
a) longer lens life b) better initial comfort
c) better optical quality d) fewer adverse effects
Better initial comfort
The tear lens formed behind a rigid contact lens corrects which type of astigmatism?
Corneal
