Test Reviews Part 2 Flashcards
Which of the following material components has the highest gas permeability?
a) Fluorine
b) PMMA
c) Butyrate
d) Silicone
d) Silicone
Application of fluorescein should be used when
Evaluating a rigid gas permeable lens fit
If the diagnostic rigid gas permeable lens placed on the eye results in minimal movement, which of the following
will increase the movement on the lens ordered for the patient?
Decreasing overall lens diameter
These will all decrease the movement of the rigid gas permeable lens
Increasing overall diameter
Increasing optic zone diameter
Increasing sagittal depth
If a soft contact lens decenters laterally, exposing a portion of the patient’s limbus, what change in parameter
would improve this situation?
Increasing lens diameter
When evaluating a diagnostic soft lens on a patient, you notice that movement is sluggish after only a few
minutes. Which of the following changes would you make to the lenses that are ordered for the patient?
Flatten base curve
the fit will be loosened and movement will be
increased.
Increasing the overall lens diameter and steepening the base curve will … the lens and … its movement
tighten
decrease
Which edge design is recommended for a + 15.00 D aphakic RGP lens?
Lenticular myoflange
This minus carrier design increases edge thickness and enables a low-riding high-plus lens to center better.
Which of the following lens designs would provide the best visual result for this patient?
K’s 42.00 @ 180 / 42.50 @ 90
Rx -3.50 -1.75 x 180
a) Spherical rigid gas permeable lens
b) Spherical soft lens
c) Soft toric lens
d) Back surface toric rigid gas permeable lens
c) Soft toric lens
Since the astigmatism is lenticular and is not found on the cornea, a spherical rigid gas permeable lens will not mask
the astigmatism since it is lenticular. There is not enough corneal astigmatism to stabilize a back surface toric lens
To aid in the positioning of a rigid prism ballast lens riding too low and slipping underneath the lower lid, which
of the following might be helpful?
a) Hyperflange
b) More prism
c) Truncation
d) Thinner edge design
c) truncation
Truncating the lower edge of the lens would help to provide a flatter, thicker surface to interact with the lower lid,
enabling the lens to rest in the proper position.
The following rigid gas permeable diagnostic lens is placed on a patient’s eye: -2.00 9.2
An over-refraction is performed with the following results: plano +1.50 x 95
Which of the following lens parameters would you order for the patient?
a) 43.50 -0.50 -1.50 x 5 9.2
b) 43.50 -2.00 -1.50 x 5 9.2
c) 43.50 plano -1.50 x 95 9.2
d) 43.50 plano + 1.50 x 5 9.2
a) 43.50 -0.50 -1.50 x 5 9.2
When applying the sphero-cylindrical over-refraction to a spherical rigid gas permeable lens, first put the overrefraction
into minus cylinder form. Plano +1.50 x 95 becomes +1.50 -1.50 x 5. Add the spherical component to the
existing spherical component (-2.00 plus +1.50 becomes -0.50). Then simply tag on the cylindrical portion of the
over-refraction.
The following soft lens is placed on a patient’s eye: 8.8 -4.00 14.0 . An over-refraction is performed resulting
in -0.75 D sphere. Which of the following lens parameters would you order for the patient?
a) 8.8 -3.25 14.0
b) 8.8 -4.00 14.0
c) 8.8 -4.75 14.0
d) 8.8 -5.25 14.0
c) 8.8 -4.75 14.0
In an RGP lens, a poorly finished transitional zone between the optic zone and the lens edge can be evaluated by:
a) Radiuscope
b) Lensometer
c) Profile analyzer
d) Contacto gauge
c) Profile analyzer
A soft toric lens, spherical and aspheric rigid gas permeable lens will all correct …
Astigmatism
An excellent material for a patient with keratoconus would be:
Fluoro Silicone Acrylate
rigid lens material
Polymacon
Crofilcon A
Bufilcon A
Soft lens materials, flexible
A prism ballast RGP lens requires how much prism for proper orientation?
0.75 to 1.50 D
Which of the following could be considered in the fitting of a keratoconus patient?
1) Aspheric
2) McGuire
3) Soper
4) Tangent Streak
1) Aspheric
2) McGuire
3) Soper
Tangent Streak
lenses are used in the treatment of
presbyopia
The following soft lens is placed on a patient’s eye: 8.4 -2.00 14.2
An over-refraction is performed with the following results: -1.00 –0.50 x 174
Which of the following lens parameters would you order for the patient?
a. -2.00 14.2
b. -2.75 14.2
c. -3.25 14.2
d. -3.75 14.2
c. -3.25 14.2
When applying the results of an over-refraction to a SOFT lens, transpose the over-refraction to minus cylinder. Then
determine the spherical equivalent (-1.25 D in this case) and add this to the existing power.
Given the following information: K’s 45.00 @ 180 / 44.00 @ 90
Rx –3.00 +1.00 x 180 Upper lid positioned at the superior limbus. Which of the following set of lens
specifications would best simulate an intrapalpebral rigid lens fitting?
a) 43.50 –1.50 8.5
b) 43.50 –1.50 9.5
c) 44.50 –2.00 8.5
d) 44.50 –2.50 8.5
d) 44.50 –2.50 8.5
Intrapalpebral lenses are designed to center between the upper and lower eye lids. To achieve this positioning, an on
K or steeper than K base curve is designed with diameters of 9.0 mm or smaller.
Given the following information, which of the following set of lens specifications would best simulate a lid
attachment rigid lens fitting?
K’s 42.00 @ 180 / 43.00 @ 90
Rx –2.00 –0.87 x 180 Upper lid positioned 2 mm below the superior limbus
a) 41.50 –1.50 9.5
b) 42.50 –2.50, 8.5
c) 43.00 –2.50 9.5
d) 43.00 –3.00 8.2
a) 41.50 –1.50 9.5
“Lid attachment” lenses are designed to fit with the upper edge of the lens positioned under the upper eye lid. To
achieve this positioning, a flatter than K, larger diameter (over 9.0 mm) is generally used
Which of the following bifocal designs represents a translating design?
a) Diffraction design
b) Crescent design
c) Reverse centrad design
d) Concentric design
B) cresent design
Given the following information, which of the listed rigid lens designs would you order to best correct this
wearer’s vision?
K’s 42.00 @ 180 / 45.00 @ 90
Rx -3.00 -2.25 x 180
42.00 / 45.00 -3.00 -2.25 (Rx form)
The base curves will parallel the K readings and the power in the lens will properly correct the astigmatism. A
spherical lens design will rock on the 180 degree meridian causing discomfort and the chance of lens displacement or
expulsion.
The performance of a soft toric lens depends on:
1) Corneal topography
2) Lid shape
3) Lid positioning
4) Lid tightness
Given the following information, which of the following RGP lens designs will best correct this wearer’s vision?
K’s 42.50 @ 180 / 42.50 @ 90
Rx -3.00 - 1.00 x 90
a) Bitoric design
b) Anterior toric design
c) Spherical design
d) Soper Cone design
b) anterior toric
The base curve will parallel the spherical cornea and the prism ballast will position the cylinder in the lens on the axis
of the Rx
A Soper cone lens design is used for …
Keratoconus
A … should always be recorded with the flat meridian first and the steep meridian second.
toric rigid lens
What is necessary to consider when fitting RGP aphakic contact lenses?
Vertex distance
Minus-carrier lenticular designs
Proper lens centration
An aphakic patient with K readings of 40.50 @ 180 / 41.25 @ 90, large palpebral fissures and flaccid lower lids
is a good candidate for:
Myoflange lenticular
A lenticular (myoflange) lens is best suited for aphakic patients with corneal curvatures
flatter than 45.00 D, large palpebral fissures and flaccid lower lids.
The patient has a horizontal visible iris diameter (HVID) of 12.5 mm. The best choice for initial soft lens
diameter would be:
14.5
The general rule of thumb for determining initial soft lens diameter is to choose a lens 2.0 mm larger than the cornea.
This will result in 1.0 mm on either side of the cornea and will aid lens centration
A single cut aphakic lens is best suited for patients with ________ apertures and _______ corneas:
Small / steep
The general rule of thumb for determining initial soft lens diameter is to choose a lens … mm larger than the cornea.
2.0 mm
Where is the power curve on a spin-cast soft lens?
The back surface
Keratoconus and penetrating keratoplasty fittings are best accomplished by which of the following methods?
a) Nomogram
b) K’s and Rx
c) Diagnostic fitting
d) Molded impression
c) Diagnostic fitting
The following ametropia frequently results in high riding rigid lenses:
High myopia
A good example of a bifocal contact lens that may rotate without vision impairment is:
Aspheric
A toric soft lens will correct:
a) Residual astigmatism
b) Moderate astigmatism (greater than 2.00 D)
c) Low astigmatism (0.75 to 2.00 D)
d) All of the above
d) All of the above
A lens fitted for keratoconus should:
a) Flatten the apex
b) Ride high
c) Align the apex
d) Ride low
c) Align the apex
Which of the following is a translating bifocal lens design?
a) Concentric
b) Aspheric
c) Diffractive
d) Segmented
d) segmented
A translating lens (Le. segmented) must move upwards for near
vision. When properly fitted, this lens design will project “alternating” images on the retina-one for distance, one for
near.
