Supplemental Skills CH16

Question 1

When calculating intraocular lens (IOL) powers, one must enter:
a) visible corneal diameter
b) desired postoperative refraction
c) pupil size
d) current refractive error

Answer 1

b) The desired postoperative refraction must be entered into the equation in order for the
proper IOL to be selected. In some cases, it may be best for a plano postoperative refraction. However, some patients may prefer to be left a little nearsighted in order to read without correction following surgery. Other possibilities exist as well.

Question 2

You are inputting data for IOL calculations and notice that the K readings are 44.5/42.75. This type of reading:
a) should prompt you to repeat the measurement
b) alerts you that lenticular astigmatism may exist
c) alerts you that axillary astigmatism may exist
d) is acceptable

Answer 2

d) In the absence of other problems (such as vastly dissimilar K readings between the two
eyes), this reading is within the normal range. You were not given enough information to
indicate whether or not lenticular astigmatism was present.

Question 3

Almost all of the formulas for calculating IOL power:
a) are based on achieving emmetropia after surgery
b) are based on measuring the aphakic eye
c) are based on the same general equation
d) are based on using an anterior chamber lens

Answer 3

c) Nearly all of the IOL calculation formulas are based on the same type of equation in
which the axial length of the eye, the depth of the anterior chamber, tissue velocity, and the
refractive powers of the cornea and IOL are factors.

Question 4

Almost all of the formulas for calculating IOL power:
a) are based on achieving emmetropia after surgery
b) are based on measuring the aphakic eye
c) are based on the same general equation
d) are based on using an anterior chamber lens

Answer 4

a) The A-constant is a number provided by the IOL manufacturer that is specific to that type of IOL. The number is entered into the IOL calculation formula.

Question 5

Which of the following poses problems in obtaining accurate measurements for IOL
calculations?
a) patients with aphakia
b) patients who have had corneal refractive surgery
c) patients with posterior subcapsular cataracts
d) patients with dense brown cataracts

Answer 5

b) It can be very difficult to obtain accurate corneal power readings (by Ks, IOLMaster, or
corneal topography) on patients who have previously had corneal refractive surgery.

Question 6

When calculating IOL power, each of the following are necessary except:
a) white-to-white corneal diameter
b) axial length
c) a calculation formula
d) K readings

Answer 6

a) The white-to-white corneal diameter measurement is used in the event an anterior chamber lens is needed. The other answers, in addition to desired postoperative refraction, are all needed input for IOL calculation. There are various formulas that can be used; which one is used depends on several factors, including surgeon preference.

Question 7

When using a penlight to estimate the depth of the anterior chamber, the following
technique is best:
a) shine the light flatly from the side, in the plane of the iris
b) shine the light from the front, and see whether there is a narrow angle
c) shine the light from the front so that the light enters the pupil
d) shine the light so that posterior synechiae can be seen

Answer 7

a) The light should be directed from the side when using a penlight to estimate chamber
depth, to see if the iris casts a shadow across the anterior chamber past the pupil (Figure
16-2).

Question 8

When using a penlight to estimate anterior chamber depth, an open angle would
appear:
a) to have a shadow on the nasal part of the iris
b) to have a shadow around the pupil
c) to have a shadow superiorly
d) to have little or no shadow

Answer 8

d) Because the iris is lying flat, little or no shadow would be cast across the angle (see
Figure 16-2).

Question 9

Estimating the anterior chamber depth with a penlight works because:
a) a narrow angle and bowed iris cast a shadow on the iris
b) a narrow angle and bowed iris cause a change in the iris color
c) an open angle and deep chamber cast a shadow on the iris
d) the pupillary response of a narrow angle is decreased

Answer 9

a) If the angle is narrow or the iris is bunched up, a shadow is cast across the angle (see
Figure 16-2).

Question 10

It is important to estimate the anterior chamber depth prior to dilation because:
a) open angles may precipitate an angle-closure glaucoma attack
b) narrow angles may precipitate an angle-closure glaucoma attack
c) narrow angles do not dilate as well and therefore require stronger dilating drugs
d) open angles dilate quickly and therefore require weaker dilating drugs

Answer 10

b) Dilating a narrow angle can lead to an angle-closure glaucoma attack. Irreversible vision loss can result.

Question 11

In slit-lamp assessment of the corneal periphery, the dark interval should be a mini-
mum of approximately how much of the total corneal width for the angle to be considered open and safe for dilation?
a) one-half
b) three-fourths
c) one-fourth
d) one-third

Answer 11

c) If you are using the slit lamp to evaluate the chamber depth, an open angle would have
a dark interval one-fourth (or more) of the total corneal width (see Figure 16-2).

Question 12

When evaluating anterior chamber depth with the slit lamp, the illumination tech-
nique used is:
a) cobalt blue filter
b) narrow beam
c) wide beam
d) pinpoint beam

Answer 12

b) A narrow beam (the narrowest available) directed at the limbus from about 60 degrees is used to evaluate chamber depth. This method puts a sharply focused beam of light on the cornea and an unfocused beam on the iris. The dark band in between these two is the object of your interest, because it represents the depth of the anterior chamber (ie, the space between the cornea and iris). Compare the width of the shadow to the width of the corneal band (see Figure 16-2). If the shadow is one-fourth to one-half as wide as the corneal band, then the angle is open (or the chamber is deep). If the shadow is less than one-fourth that of the corneal band, then the angle is narrow (or the chamber is shallow). If the shadow is missing, then the cornea and iris are so close together that the angle is closed or nearly closed (or the chamber is flat).

Question 13

Measuring corneal thickness via nonoptical pachymetry involves the use of:
a) specular microscopy
b) ultrasound
c) the slit-lamp microscope
d) a contact mirrored lens

Answer 13

d) The probe must be held perpendicular to the portion of the corneal surface being measured. When measuring central cornea, this is not too difficult. The hard part is measuring the periphery, where the cornea is more curved.

Question 14

One of the keys in accurate pachymetry is:
a) aiming the probe at the optic nerve
b) aiming the probe at the macula
c) maintaining contact with the coupling gel
d) holding the probe perpendicular to the corneal surface

Answer 14

c) The thickness of the cornea is vital information in refractive surgery, where instruments are used to alter the shape of the cornea in order to change the patient’s refractive error. An error could result in a perforation or inaccurate correction.

Question 15

Pachymetry readings are routinely taken prior to:
a) cataract surgery
b) retinal surgery
c) refractive surgery
d) plastic surgery

Answer 15

b) The central cornea should be the easiest to measure, because it is easier to maintain
proper alignment in this position. It is also the thinnest part of the cornea, providing a
number with which to compare subsequent readings. Therefore, it is best to start the measurements with the central cornea.

Question 16

When performing pachymetry prior to refractive surgery, it is generally best to begin:
a) with the corneal periphery at 12:00
b) with the central cornea
c) with the mid-periphery at 12:00
d) a scleral reading for calibration

Answer 16

d) Research has shown that a person with a thinner cornea is more likely to develop glaucoma than someone with a thick cornea. Therefore, measuring the central corneal thickness has become standard of care in evaluating glaucoma.

Question 17

The type of pachymetry used to evaluate a glaucoma suspect is:
a) optical coherence tomography
b) central corneal curvature
c) peripheral corneal thickness
d) central corneal thickness

Answer 17

d) Research has shown that a person with a thinner cornea is more likely to develop glau-
coma than someone with a thick cornea. Therefore, measuring the central corneal thickness has become standard of care in evaluating glaucoma.

Question 18

The average central thickness of the human cornea is:
a) 43 D
b) 50 mm
c) 545 μm
d) 655 μm

Answer 18

c) The average corneal thickness is about 545 μm. (Answer d, 655 μm, is the average corneal thickness at the limbus.)

Question 19

The IOLMaster must be calibrated daily using a:
a) calibration weight
b) set of metal spheres of known curvature
c) “test eye”
d) calibration bar

Answer 19

c) Each instrument is supplied with a “test eye” that is used daily for calibration prior to
measuring any patients.

Question 20

If a biometry instrument fails to calibrate properly, one should:
a) adjust the measurements appropriately
b) remove the instrument from use
c) make a note in the patient’s record along with the measurement
d) apply the manufacturer’s “fudge factor” to the formula

Answer 20

b) Anytime that a biometry instrument fails the calibration test, it should be removed from service. Call the manufacturer for further instructions.

Question 21

The Schirmer’s test might be indicated in all of the following except:
a) dry eye
b) contact lens pre-evaluation
c) epiphora
d) dacryocystitis

Answer 21

d) Dacryocystitis is an infection of the tear sac and does not affect tear production.

Question 22

The difference between Schirmer’s test I and II is:
a) the length of the test
b) the type of strips used
c) the use of an anesthetic
d) there is no difference

Answer 22

c) Schirmer’s test I does not use topical anesthetic; Schirmer’s test II does.

Question 23

Schirmer’s test I is used to measure:
a) reflux tears
b) reflex tears
c) normal tearing
d) epiphora

Answer 23

b) Because no anesthetic is used, the Schirmer’s test I measures tears that form as a response to irritation. These are called reflex tears.

Question 24

Schirmer’s test II is used to measure:
a) reflux tears
b) reflex tears
c) normal tearing
d) drainage rate

Answer 24

c) The use of anesthetic in Schirmer’s test II eliminates the tearing due to irritation by the
test strip. Thus, normal tearing is measured.

Question 25

Measuring time for the Schirmer’s test is:
a) 1 minute
b) 2 minutes
c) 5 minutes
d) 10 minutes

Answer 25

c) Both Schirmer’s tests have a 5-minute test time.

Question 26

All of the following are true regarding the Schirmer’s test except:
a) it requires expensive equipment
b) it is brief
c) it is portable
d) it can be done at bedside

Answer 26

a) Test strips are the only expense of the Schirmer’s test (plus topical anesthetic, if used), and they are relatively inexpensive (as far as medical supplies go).

Question 27

A normally functioning lacrimal gland will produce how much wetting on a Schirmer’s test strip after 5 minutes?
a) 1 mm
b) 2.5 mm
c) 6 mm
d) 10 mm

Answer 27

d) A Schirmer’s test of 10 mm or more is considered normal.

Question 28

All of the following are used in evaluating tear break-up time (TBUT) except:
a) slit-lamp microscope
b) tear filter papers
c) fluorescein dye
d) cobalt blue light

Answer 28

b) TBUT does not use tear filter papers. Do not be confused by fluorescein-impregnated
strips!

Question 29

Just prior to the beginning of the TBUT test, the patient is instructed to:
a) take a deep breath and hold it
b) squeeze the eyes shut tightly
c) look up
d) blink

Answer 29

d) Just before you begin timing the TBUT test, have the patient blink. This spreads the
fluorescein dye over the cornea. Timing is begun just after the blink, and the patient is asked not to blink again until told to do so.

Question 30

When performing the TBUT test, the observer is looking for:
a) the appearance of dry spots
b) pooling of the fluorescein dye
c) reflex tearing
d) drainage of tears off the eye

Answer 30

a) Time is counted until the fluorescein shows that the tear film is breaking down, evidenced by the appearance of dry spots where the dye seems to “open up.”

Question 31

A TBUT of which of the following would indicate tear film dysfunction?
a) 10 seconds
b) 20 seconds
c) 30 seconds
d) 40 seconds

Answer 31

a) The TBUT is considered abnormal if less than 10 to 15 seconds. (References vary
between 10 and 15 seconds, but all agree that 10 seconds or less is abnormal.)

Question 32

Rose bengal is:
a) a treatment for dry eye
b) used in checking intraocular pressure
c) used to dilate the pupil
d) a staining agent

Answer 32

d) Rose bengal (it is actually a derivative of fluorescein) is a staining agent used to identify dead or degenerated epithelial cells.

Question 33

A patient with which of the following potential diagnoses would be tested with rose
bengal?
a) glaucoma
b) corneal foreign body
c) severe dry eye
d) contact lens fitting

Answer 33

c) Severe dry eye (keratoconjunctivitis sicca, often associated with autoimmune diseases
such as rheumatoid arthritis) is the classic diagnosis for which rose bengal testing is performed. The dye causes dead or degenerated epithelial cells as well as mucus to stain red.

Question 34

Each of the following might be evaluated using rose bengal except:
a) corneal endothelial drop-out
b) corneal abrasion
c) corneal herpes simplex
d) keratitis

Answer 34

a) The point of this question is to emphasize that rose bengal is used to evaluate conditions involving epithelial (not endothelial) cells, including cornea and conjunctiva. Most practitioners will use standard fluorescein dye for these indications, however.

Question 35

Each of the following is true regarding rose bengal except:
a) stinging may be severe
b) it requires the use of the cobalt blue filter
c) it stains tissue a reddish-pink color
d) it is available in drop and strip form

Answer 35

b) Rose bengal does not require use of the cobalt blue or any other filter. The other statements are true.

Question 36

Glare testing is used to identify:
a) irregular curvature of the crystalline lens
b) decrease in vision due to glare conditions
c) decrease in contrast sensitivity
d) macular stress adaptation

Answer 36

b) The glare test helps measure the patient’s acuity in the presence of marked glare. In
certain situations (notably media opacities, such as posterior subcapsular cataracts, corneal scarring, posterior capsule opacity, etc), glare will cause a drop in vision by causing the patient’s pupil to constrict. This forces the patient to try to look directly through the opacity.

Question 37

In which of the following would glare testing be most appropriate?
a) pterygium
b) keratoconus
c) posterior subcapsular cataract
d) IOL calculations

Answer 37

c) Glare testing in the presence of posterior subcapsular cataracts is especially dramatic
because the glare causes the pupil to constrict (see answer 36).

ANSWER 36: The glare test helps measure the patient’s acuity in the presence of marked glare. In certain situations (notably media opacities, such as posterior subcapsular cataracts, corneal scarring, posterior capsule opacity, etc), glare will cause a drop in vision by causing the patient’s pupil to constrict. This forces the patient to try to look directly through the opacity.

Question 38

When performing a brightness acuity glare test, it is best to do which of the following?
a) Allow the patient to adjust to the light level before reading the letters.
b) Do glare testing through the phoroptor.
c) Time how long it takes for the patient to read the letters.
d) Calibrate the instrument.

Answer 38

a) Allow the patient a few seconds to adjust to the level of light before asking him or her to
read the chart.3 If the patient has had a change in his or her refractive error, trial frames and lenses should be used as the phoroptor blocks some of the light from the brightness acuity tester (BAT). The BAT is factory calibrated. The macular photostress test is where a bright light is shown into the patient’s eye for 10 seconds (the BAT may be used, although this is not considered a glare test), then time is counted until the patient can read letters two lines larger than his or her original acuity. Normal recovery is 0 to 30 seconds, but can be much longer in patients with macular problems.

Question 39

Which eye structure is responsible for color vision?
a) choroid
b) rods
c) cones
d) optic nerve

Answer 39

c) The cone cells are responsible for color vision. The rods function in dim lighting and
give only shades of gray. The optic nerve is a conductor, but does not collect light itself,
nor does the choroid.

Question 40

The photosensitive pigments of the eye are sensitive to:
a) red, green, and blue
b) red, blue, and yellow
c) red, green, and yellow
d) green, blue, and yellow

Answer 40

a) The eye’s pigments are sensitive to red, green, and blue. Do not be confused by the so called primary colors listed in answer b.

Question 41

Color vision testing is used to detect all of the following except:
a) presence of normal color vision
b) type and severity of color defect
c) those who may not qualify for certain jobs
d) differentiate between congenital or acquired color blindness

Answer 41

d) A color vision test in and of itself cannot differentiate between congenital or acquired
color defects. Certain professions may reject applicants who do not have normal color
vision. (Of note, some tests merely give a yes/no and type of defect present, while others identify the severity of the deficit.)

Question 42

The Ishihara color plates are useful:
a) for screening purposes, such as job applications
b) for detailed information on a patient’s color defect
c) as a basis for referral to a neuro-ophthalmologist
d) only for those who already know they have a defect

Answer 42

a) The standard pseudoisochromatic color plates are to be used as a screening device. For more detailed color-vision information, other tests are needed (such as arrangement tests).

Question 43

To test a patient with the color pseudoisochromatic plates:
a) the plates should be held at 10 inches
b) the patient should be tested without correction
c) the patient should be tested with near correction, if worn
d) the patient must have at least 20/30 vision at near

Answer 43

c) The patient should wear habitual near correction when being tested with the color plates. The plates should be held at 14 to 16 inches.

Question 44

Illumination for the color plates test:
a) varies according to the type of test administered
b) should come from an easel lamp in a dark room
c) should be natural daylight
d) should be one-fifth of the room light

Answer 44

a) Read the instructions for your particular set of color plates to get illumination requirements.

Question 45

Before proceeding with the actual color plate test:
a) the patient is shown a sample that is discernable to normal and abnormal alike
b) the patient is shown a sample that is discernable only to those with a color deficit
c) the lights should be dimmed
d) the patient should be dilated

Answer 45

a) The color plate test starts with a figure that everyone can see, regardless of whether a
color deficit exists or not.

Question 46

A color plate that shows no obvious number to normal and abnormal alike is useful
because:
a) it identifies those with vision too poor to do the regular test
b) a malingerer may invent a number, thus identifying him- or herself
c) it causes the patient to be more alert
d) it creates doubt, so that the patient is unaware of his or her score

Answer 46

b) A patient may try to fool you by inventing a number for the “blank” plate.

Question 47

How long should the patient be given to recognize the figure in a color plate?
a) 2 to 3 seconds
b) 10 to 15 seconds
c) 30 to 40 seconds
d) as long as he or she needs

Answer 47

a) The patient should be given 2 to 3 seconds to identify the number in the color plates.

Question 48

Young children can be tested using the color plates:
a) only if they know numbers
b) only if they know colors
c) by having them trace the number/figure
d) by having them describe the number/figure

Answer 48

c) Ask young children to trace the pattern formed by the different-colored dots with a cotton swab (to avoid marring the test plates).

Question 49

When using color plates, a score indicates abnormal color vision:
a) when the patient misses 5% of the plates
b) when the patient misses 10% of the plates
c) when the patient misses 20% of the plates
d) varies according to the type of test

Answer 49

d) The number a patient can miss before being considered abnormal also varies from one test to another. Consult the instructions.

Question 50

Hereditary color defects most often fall into which category?
a) red-green
b) blue-yellow
c) monochromic
d) multichromic

Answer 50

a) Most hereditary defects are red-green.

Question 51

Hereditary color vision defects affect:
a) males and females equally
b) more males than females
c) males only
d) females only

Answer 51

b) The incidence of hereditary color vision defects is 8% in males and 0.5% females, but
either gender may be affected.

Question 52

Hereditary color vision defects usually affect:
a) both eyes equally
b) one eye more than the other
c) one eye only
d) the dominant eye

Answer 52

a) Both eyes are usually affected equally in hereditary color vision problems, so the screening color test can be done with both eyes together.

Question 53

Which of the following should be color-vision tested one eye at a time?
a) suspected blue-yellow defect
b) suspected red-green defect
c) suspected congenital color defect
d) suspected acquired color defect

Answer 53

d) If one suspects an acquired color defect, the eyes should be tested separately.

Question 54

Acquired color vision defects:
a) can often be cured by wearing a green contact lens on one eye
b) can often be cured if the causative factor is eliminated
c) can often be cured by retinal surgery
d) can often be cured by injections of photosensitive pigment

Answer 54

b) If the cause of an acquired color deficit is removed, color vision may return to normal.

Question 55

If the patient is suspected of having an acquired color vision defect, all of the following apply except:
a) each eye can have a different degree of deficit
b) the defect tends to remain stable over time
c) he or she will tend to make color errors scattered all across the color wheel
d) they can resolve

Answer 55

b) An acquired defect (as opposed to a congenital defect) tends to gradually worsen unless the cause is treated. Because an acquired defect may affect the eyes differently, each eye should be tested separately. (Congenital defects can be tested with both eyes together.) Instead of making matching errors in a specific color range, as with a congenital defect, those with acquired defects tend to make matching errors scattered all across the color wheel. (There are, of course, exceptions.)

Question 56

When should a child have his or her color vision checked?
a) Only if there is a family history of color blindness.
b) Prior to age 4.
c) Before starting school.
d) By age 10.

Answer 56

c) Before starting school is a good time to test a child’s color vision. Answer a is wrong
because of the word “only.”

Question 57

Color vision defects in children are frequently detected among those with:
a) reading disabilities
b) retinoblastoma
c) sickle cell disease
d) attention deficit disorder

Answer 57

a) Children with reading disabilities often have color vision deficits as well.

Question 58

The axial length of an average adult eye is:
a) 21 to 22 mm
b) 23 to 24 mm
c) 26 to 27 mm
d) 29 to 30 mm

Answer 58

b) The average adult eye is 23 to 24 mm.

Question 59

The axial length of the eye is important in the calculation of:
a) contact lens parameters
b) corneal graft power
c) IOL power
d) keratometric parameters

Answer 59

c) Axial length is essential in the calculation of IOL powers. Contact lens parameters are
external. Axial length does not figure into keratometric readings. Transplanted corneal
grafts do not have calculated power.

Question 60

In evaluating an axial length scan, the retinal echo must be:
a) to the right of the scleral and orbital echoes
b) the shortest of the scan
c) in the center of the scan
d) to the left of the scleral and orbital echoes

Answer 60

d) The retinal echo is to the left of the scleral and orbital echoes (because the sclera and
orbit are behind the retina).

Question 61

In an axial length A-scan, if there is only one tall echo from the back of the eye with no other echoes behind it, this indicates:
a) the presence of a tumor and that an x-ray should be done
b) that the sound beam is directed to the macula and the measurement is correct
c) that the sound beam is directed to the optic disc and the measurement is incorrect
d) that the sound beam is directed at the macula and the measurement is incorrect

Answer 61

c) If the A-scan beam is falling on the optic disc, only one echo will appear from the back
of the eye. Because the reading should be taken from the macula, this would be an inaccurate measurement.

Question 62

A measurement error of 1 mm in an axial eye length could result in an unwanted
postoperative refractive error of as much as:
a) 0.1 D
b) 1.0 D
c) 0.3 D
d) 3.0 D

Answer 62

d) An error of 1 mm on the A-scan measurement can be translated to an undesired postoperative refractive error of about 3.0 D.

Question 63

When comparing the axial lengths of a patient’s left and right eye, how much of a dif-
ference between the eyes should signal you to repeat the measurement of both eyes?

a) 1.0 mm
b) 0.5 mm
c) 0.3 mm
d) 0.1 mm

Answer 63

c) A difference in axial length between the two eyes of less than 0.3 mm is considered a
normal variation. A difference of 0.3 mm or more is just cause for repeat measurements.

Question 64

An A-scan can be artificially shortened due to:
a) pressing on the globe too hard with the probe
b) not using enough topical anesthetic
c) measuring through a dilated pupil
d) high hyperopia and astigmatism

Answer 64

a) Pushing on the globe artificially shortens the eye. A high hyperope usually has a shorter eye, but it is naturally shorter, not artificially so.

Question 65

Which of the following A-scans would you use (Figure 16-1)? A or B

Answer 65

b) In Figure 16-1B, all echoes are clearly defined, tall, and steeply rising. Figure 16-1A shows insufficient anterior lens, retinal, scleral, and orbital fat echoes.

Question 66

Laser interferometry uses which type of laser light?
a) microwave
b) ultrasonic
c) infrared
d) polarized

Answer 66

c) Laser interferometry uses infrared laser light.

Question 67

The IOLMaster eliminates which of the following sources of error?
a) shortened axial length due to compression
b) distorted corneal curvature due to improper alignment
c) inaccurate corneal diameter measurements due to parallax error
d) mathematical formula selection errors

Answer 67

a) The IOLMaster measures axial length without contacting the cornea, so there is no artificial shortening of the measurement due to pressing on the globe with an ultrasonic probe.

Question 68

When positioning the IOLMaster for the axial length reading:
a) only the center of the visual axis may be used
b) only a totally clear cornea is readable
c) focus can be moved off-axis to obtain a clear reading
d) the probe tip must be perpendicular to the corneal surface

Answer 68

c) Unlike conventional ultrasonic measurements, the IOLMaster reading is not dependent on measuring from the visual axis. Sometimes, maneuvering the focus a little bit around the visual axis will give a more ideal display. This way, the scan can be obtained even in the presence of small media opacities. There is no physical contact between the instrument and the patient’s eye.

Question 69

The IOLMaster evaluates each of the following except:
a) horizontal corneal diameter
b) corneal curvature
c) refractive error
d) anterior chamber depth

Answer 69

c) The IOLMaster does not perform automated refractometry readings.

Question 70

For safety reasons, the limit for the number of readings that may be taken per eye per
day with the IOLMaster is:
a) 5
b) 10
c) 15
d) 20

Answer 70

d) No more than 20 measurements should be taken on an eye in a single day. (In fact, the
instrument has a built-in safety feature that prevents this.)

Question 71

Each of the following can cause an error in the axial length scan reading of the IOL-
Master except:
a) patient wearing contact lenses
b) patient wearing spectacles
c) patient not fixating
d) patient with retinal detachment

Answer 71

b) In cases of high refractive errors (more than 6 D), the measurement may be taken with the patient wearing his or her spectacles. (This is only done so that the patient can see the fixation light/device.)

Question 72

The ideal IOLMaster axial length graph is:
a) a tall, central spike with only one peak and smaller spikes on either side
b) a tall, central spike with two peaks and smaller spikes on the left
c) a tall spike with only one peak and smaller spikes to the left
d) a small, central spike and taller spikes on either side

Answer 72

a) The ideal axial length scan on the IOLMaster is a tall, central spike that has only one peak. (It is important to zoom in on this spike to make sure that there are not multiple peaks; otherwise, you may miss this.) There should be smaller spikes on either side.4

Question 73

With the IOLMaster, the ideal signal-to-noise ratio is:
a) 0 or less
b) 0.5
c) 1.5
d) 2.0 or more

Answer 73

d) A signal-to-noise ratio of 2.0 or more is desirable. But the axial length display must also be considered in identifying useable measurements.