ROUB STUDY EXAM GUIDE UPDATED QUESTIONS AND
ANSWERS GRADED A+
✔✔The difference in keratometry readings with the fellow eye should be how many
diopters? - ✔✔1D
✔✔An error of 1 diopter in a keratometry measurement results in an error of how much
post-operative refraction? - ✔✔1D
✔✔What is the equivalent of +/-0.02 mm in dioptric keratometry refractive power? -
✔✔Approx. 0.12D
✔✔How many readings should be average for a final keratometry reading? - ✔✔Two to
three
✔✔How many weeks should a patient discontinue wearing their hard contact lenses
prior to a keratometry measurement? - ✔✔At least 2 weeks
✔✔If distortion of the cornea mires is present, what may be applied to improve mire
appearance? - ✔✔One drop of anesthetic or artificial tears
✔✔If a patient has ointment applied to the eye, what is the suggested waiting period
prior to performing a keratometry measurement? - ✔✔Three hours
✔✔Keratometry measures the radius of what curvature? - ✔✔Anterior surface of the
cornea
✔✔In the case of severe corneal pathology, what method should be used instead of
keratometry? - ✔✔Corneal topography
✔✔What technique is used to measure the radius of curvature of the anterior corneal
surface? - ✔✔Keratometry
✔✔What is the average keratometry reading? - ✔✔Between 43 and 44
✔✔What condition, resulting from an exam, would affect a patient's keratometry
reading? - ✔✔Uncorrected refractive error
✔✔Following RK surgery, how is the average keratometry measurement determined for
an IOL calculation? - ✔✔Subtract the change in refractive error, vertexed back to the
cornea from the average preoperative keratometry readings
, ✔✔A patient's corneal power measured 45D prior to RK. Following the surgery,
refraction changed by 3.5D. What average keratometry reading will be used to
determine the lens power calculations? - ✔✔45D-3.5D=41.5D
✔✔How many gates are within an ultrasound machine? - ✔✔Between 2 and 5
✔✔What is the correct method of gate placement in relation to the spikes? - ✔✔On the
ascending limb of the spike or on the peak of the spike
✔✔What setting controls the width of the sound beam, sensitivity, resolution, and depth
of penetration? - ✔✔Gain
✔✔What type of error will occur with a gain that is set too high? - ✔✔A short reading
✔✔What type of error will occur with a gain that is set too low? - ✔✔A long reading
✔✔What are the two measurement modes for A-scan biometry? - ✔✔Manual and
automatic
✔✔"Pattern recognition" refers to what mode of measurement? - ✔✔Automatic
✔✔What measurement mode allows the biometrist more freedom to maneuver the
probe for proper alignment of the sound beam along the visual axis and to select the
scans to be measured? - ✔✔Manual measurement mode
✔✔What information is needed to determine the sound velocity setting? - ✔✔Eye type
(phakic, aphakic, or pseudophakic)
✔✔What sound velocity setting is used for an aphakic eye? - ✔✔1532 m/sec
✔✔An aphakic eye measurement requires two gates. What is the position of the gates?
- ✔✔The anterior gate is placed at the corneal spike and the posterior gate is placed at
the retinal spike
✔✔What type of error will occur if the sound velocity setting is set too low? - ✔✔Short
measurement
✔✔What type of error will occur if the sound velocity setting is set too fast? - ✔✔Long
measurement
✔✔What measurement mode is programmed to recognize spikes that occur within a
preset range from the probe? - ✔✔Automatic mode
ANSWERS GRADED A+
✔✔The difference in keratometry readings with the fellow eye should be how many
diopters? - ✔✔1D
✔✔An error of 1 diopter in a keratometry measurement results in an error of how much
post-operative refraction? - ✔✔1D
✔✔What is the equivalent of +/-0.02 mm in dioptric keratometry refractive power? -
✔✔Approx. 0.12D
✔✔How many readings should be average for a final keratometry reading? - ✔✔Two to
three
✔✔How many weeks should a patient discontinue wearing their hard contact lenses
prior to a keratometry measurement? - ✔✔At least 2 weeks
✔✔If distortion of the cornea mires is present, what may be applied to improve mire
appearance? - ✔✔One drop of anesthetic or artificial tears
✔✔If a patient has ointment applied to the eye, what is the suggested waiting period
prior to performing a keratometry measurement? - ✔✔Three hours
✔✔Keratometry measures the radius of what curvature? - ✔✔Anterior surface of the
cornea
✔✔In the case of severe corneal pathology, what method should be used instead of
keratometry? - ✔✔Corneal topography
✔✔What technique is used to measure the radius of curvature of the anterior corneal
surface? - ✔✔Keratometry
✔✔What is the average keratometry reading? - ✔✔Between 43 and 44
✔✔What condition, resulting from an exam, would affect a patient's keratometry
reading? - ✔✔Uncorrected refractive error
✔✔Following RK surgery, how is the average keratometry measurement determined for
an IOL calculation? - ✔✔Subtract the change in refractive error, vertexed back to the
cornea from the average preoperative keratometry readings
, ✔✔A patient's corneal power measured 45D prior to RK. Following the surgery,
refraction changed by 3.5D. What average keratometry reading will be used to
determine the lens power calculations? - ✔✔45D-3.5D=41.5D
✔✔How many gates are within an ultrasound machine? - ✔✔Between 2 and 5
✔✔What is the correct method of gate placement in relation to the spikes? - ✔✔On the
ascending limb of the spike or on the peak of the spike
✔✔What setting controls the width of the sound beam, sensitivity, resolution, and depth
of penetration? - ✔✔Gain
✔✔What type of error will occur with a gain that is set too high? - ✔✔A short reading
✔✔What type of error will occur with a gain that is set too low? - ✔✔A long reading
✔✔What are the two measurement modes for A-scan biometry? - ✔✔Manual and
automatic
✔✔"Pattern recognition" refers to what mode of measurement? - ✔✔Automatic
✔✔What measurement mode allows the biometrist more freedom to maneuver the
probe for proper alignment of the sound beam along the visual axis and to select the
scans to be measured? - ✔✔Manual measurement mode
✔✔What information is needed to determine the sound velocity setting? - ✔✔Eye type
(phakic, aphakic, or pseudophakic)
✔✔What sound velocity setting is used for an aphakic eye? - ✔✔1532 m/sec
✔✔An aphakic eye measurement requires two gates. What is the position of the gates?
- ✔✔The anterior gate is placed at the corneal spike and the posterior gate is placed at
the retinal spike
✔✔What type of error will occur if the sound velocity setting is set too low? - ✔✔Short
measurement
✔✔What type of error will occur if the sound velocity setting is set too fast? - ✔✔Long
measurement
✔✔What measurement mode is programmed to recognize spikes that occur within a
preset range from the probe? - ✔✔Automatic mode
