Biometry Flashcards
. Ultrasound would travel the slowest in ____________
a. the cornea
b. a normal adult’s lens
c. a normal infant’s lens
d. a cataractous lens
e. the aqueous humor
e. The aqueous humor
Which of the following statements concerning ultrasound is NOT correct?
a. a-scan gives a one dimensional view and b-scan gives a 2-dimensional view.
b. a-scan is more accurate than b-scan for viewing optic nerve details
c. Both a- and b-scan instruments employ the “pulse-echo” technique.
d. b-scan techniques can be used to view retinal detachments.
e. a-scan techniques can measure the axial length of the eye
b. a-scan is more accurate than b-scan for viewing optic nerve details
Which of the following instruments is not used to evaluate the curvature of the cornea?
a. Keratometer
b. Ophthalmometer
c. Placido’s Disc
d. Videokeratoscope
e. A-scan Ultrasound
e. A-scan Ultrasound
An optical pachymeter can be used to measure _____________
a. the apparent corneal thickness using a calibrated doubling device.
b. the apparent radius of curvature of the anterior surface of the lens
c. directly the true depth of the anterior chamber using a Scheiner focusing system.
d. the refractive index of the crystalline lens.
e. the position of the eye’s nodal point.
a. the apparent corneal thickness using a calibrated doubling device.
Complete this sentence. Ultrasound is a wave which _______
a. has a higher frequency than light.
b. has a shorter wavelength than light.
c. has a higher frequency than sound.
d. has a longer wavelength than sound.
c. has a higher frequency than sound.
Which of the following instruments measures corneal thickness?
a. Placido’s Disc
b. Optical Pachymeter
c. Keratoscope
d. Ophthalmometer
e. Ophthalmodynamometer
b. Optical Pachymeter
Which of the following physical effects is used to produce and capture ultrasound?
a. Johnson noise
b. Heisenberg effect
c. Hall effect
d. Piezoelectric effect
e. Fresnel effect
d. Piezoelectric effect
All of the following optical principles are used in Optical Coherence Tomography (OCT) except which one?
a. Low coherence
b. Interference
c. 50/50 fiber coupling
d. Diffraction
e. Reflection
D. Diffraction
Partial coherence interferometry (or Laser Doppler Interferometry, LDI) techniques differ from A and B scan Ultrasound techniques in that PCI ( LDI) provides higher resolution than ultrasound. T or F?
A. T
B. F
True
. Partial coherence interferometry (or Laser Doppler Interferometry, LDI) techniques may be preferable to A and B scan Ultrasound techniques because PCI( LDI) is a non-contact method and ultrasound relies upon use of a contact probe. T or F?
A. T
B. F
True
Ultrasound is a wave that has A. a longer wavelength than sound waves B. a lower frequency than sound waves C. a higher frequency than visible light waves D. higher energy than UV light E. longer wavelength than visible light
E. longer wavelength than visible light
All of the following are true of Adaptive Optics (AO) except which one? AO…
a. is a method used to enhance the refractive accuracy of spectacle lenses
b. employs deformable mirrors to correct wave front aberrations
c. can be combined with Optical coherence tomography (OCT)
d. can be combined with scanning laser ophthalmoscopy (SLO)
e. can be combined with tracking techniques to remove the effects of small eye movement
a. is a method used to enhance the refractive accuracy of spectacle lenses
The piezoelectric effect in ultrasound involves all of the following except which one?
a. pressure on piezoelectric crystals produces voltage change
b. voltage change produces vibration of crystals and shape change
c. after shape change crystals emit waves (“pulses”) into the surrounding medium
d. waves reflected from obstacles (“echo”) return to the x-ray film for photographic images
e. returning waves cause secondary vibration of crystals and voltage change captured as images on a screen
d. waves reflected from obstacles (“echo”) return to the x-ray film for photographic images
All of the following are true of optical coherence tomography, OCT, except which one?
a. OCT utilizes the effect of low coherence light waves
b. The light waves in OCT have a long coherence length
c. The light waves in OCT are coherent (sinusoidal) over a short distance
d. The coherence length of the light waves in OCT is suitable to create interference
e. Interference is the property utilized in OCT that allows translation into images
b. The light waves in OCT have a long coherence length
. All of the following are true of Partial Coherence Interferometry, except which one?
a. PCI is the principle behind capturing images in ultrasound
b. can measure axial eye length by detecting the reflections from corneal and retinal surfaces
c. can be used for monitoring axial elongation (lengthening) in progressive myopia
d. may be used to measure off-axis eye length
e. is used in ocular biometery devices, such as the Zeiss IOL Master
a. PCI is the principle behind capturing images in ultrasound
