Ultrasound

Question 1

What is a combo of A and B scan

Answer 1

Standard echographs

Question 2

Ocular ultrasound indications

Answer 2

Opaque ocular media: Opacified K, hyphema, hypopyon, mitosis, lens opacities, persistent pupillary membrane, vitreal hemes.

Intra ocular foreign bodies

Clear ocular media: Iris lesions, CB lesions, ONH abnormality

Tumors
Choroid or retinal detachment

Question 3

Orbital ultrasound indication

Answer 3

Exophthalmos 
Enophthalmos 
Globe displacement 
Ptosis 
Lid retraction
Lid swelling 
Periorbital mass 
Motility disturbance/diplopia 
Periorbital pain

Question 4

Contraindications to ultrasound

Answer 4

No absolute contraindications.

Extra care should be taken following surgeries or open wounds.

Question 5

Ophthalmic ultrasounds use which frequencies

Answer 5

8-10MHz.

Question 6

Relationship between frequencies, penetrance and resolution.

Answer 6

As you increase the Hz, the resolution increases. Penetrance decreases.

Question 7

What system is used to get the ultrasound

Answer 7

Pulse echo system using a crystal component in the transducer. Creates vibrations that are converted into electrical impulses that are amplified. Displayed in real time.

Question 8

Angle of incidence is ____ to the angle of reflection

Answer 8

Equal

Question 9

Smooth straight interfaces reflect all the wave. This is called

Answer 9

Specular reflection

Question 10

Irregular and small surfaces cause part of the echo to be

Answer 10

Scattered.

Question 11

Sound velocity through solid vs liquid media

Answer 11

Travels quicker through solid than liquid

Question 12

How to minimize absorption

Answer 12

Absorption is converted to heat. Minimize by performing on K.

Question 13

Refraction

Answer 13

Same as light rays. Medium to high index causes sound/light to bend towards the perpendicular.

Question 14

Absorption and refraction are minimal at interfaces that are

Answer 14

Reflective and regularly structures.

You want them to be minimal or else they will reduce beam strength.

Question 15

Shadowing can be caused by

Answer 15

Strong reflective surfaces- air, FB, calcifications.

Question 16

B scans offer __ and ___ representation of ocular or orbital structures

Answer 16

Topographical and qualitative

Question 17

An oscillating sound beam is emitted from the probe the direction of which is indicated by

Answer 17

The mark on the probe tip. Either superior or nasal.

Question 18

Increasing the gain

Answer 18

Decreases the resolution. Allows weaker signals to be displayed- more scatter and nice.

Question 19

Decreasing the gain

Answer 19

Increases resolution. Only strong signals appear.

Question 20

What gazes to take pics of when the marker is superior

Answer 20

ONH/PP
Nasal
Temporal

Question 21

What gazes to take pics of when the marker is nasal

Answer 21

ONH/PP
Superior
Inferior

Question 22

If the marker is nasal, the upper part of the screen is

Answer 22

Nasal

Question 23

A scan offers a ____ representation of the ocular structures

Answer 23

Quantitative. Gives a number

Question 24

A scan is best used for determining

Answer 24

Tissue texture, internal structures, density and dimension of lesion.

Question 25

How to apply B scan vs A scan

Answer 25

B scan- can be applied to K (proparacaine, without gel) or to lid (no proparacaine, with gel) A scan- applied only to K with proparacaine and no gel. Do not indent K surface.

Question 26

For A scans, what is the optimum gain for tissue differentiation

Answer 26

Tissue sensitivity gain setting.

Question 27

A scans are vital component of

Answer 27

Calculations in determining intraocular lens implant before cataract surgery.

Question 28

Normal axial length

Answer 28

22-24.5