Podcast
Questions and Answers
What frequency range is typically used for diagnostic imaging in ophthalmic ultrasound?
What frequency range is typically used for diagnostic imaging in ophthalmic ultrasound?
What type of image does the A-Scan produce?
What type of image does the A-Scan produce?
Which method is NOT typically associated with A-Scan applications?
Which method is NOT typically associated with A-Scan applications?
What is the primary advantage of B-Scan over A-Scan?
What is the primary advantage of B-Scan over A-Scan?
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What characteristic distinguishes Optical Coherence Tomography (OCT) from A-Scan and B-Scan?
What characteristic distinguishes Optical Coherence Tomography (OCT) from A-Scan and B-Scan?
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Which condition can Optical Laser Interferometry directly measure?
Which condition can Optical Laser Interferometry directly measure?
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What does the term 'aphakic' refer to in cataract terminology?
What does the term 'aphakic' refer to in cataract terminology?
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Which management method is designed specifically to reduce axial length growth in myopia?
Which management method is designed specifically to reduce axial length growth in myopia?
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What is the purpose of Potential Acuity Testing?
What is the purpose of Potential Acuity Testing?
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What distinguishes the A-Scan technique from the B-Scan technique?
What distinguishes the A-Scan technique from the B-Scan technique?
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Study Notes
Ophthalmic Ultrasound
- Wavelength for diagnostic purposes should be within 1mm or less
- Wavelength of sound decreases as frequency increases
- Diagnostic imaging uses frequencies between 20 kHz to 1 MHz
A-Scan (Pencil Scan)
- Amplitude modulated
- One-dimensional, linear image
- Single beam at 10-12 MHz
B-Scan
- Brightness modulated
- 2D image represented by dots or multiple A-scans
- Multiple sound waves at around 10 MHz or higher (35-100 MHz)
A-Scan (Details)
- Used to determine eye length and common sight disorders (anterior segments)
- Essential for cataract surgery – enables ophthalmologists to determine intraocular lens power
- Diagnoses and measures eye masses (tumors)
- Methods: Contact (optical gel, probe on eye) or immersion (cup over eye, filled with fluid)
B-Scan (Details)
- Evaluates eye diseases (posterior segment & orbit)
- Sees through cloudy/opaque material (e.g., cataracts)
- 10x more detailed and deeper than A-scan
- Used for calcification
- A-scan happens after B-scan
Optical Coherence Tomography
- Uses near-infrared light instead of sound to create cross-section images of the eye
- Non-contact
- High-resolution
- Allows viewing of the retina, optic nerve, and anterior segment
- Tomography by sections using penetrating waves
- Can identify tumors and inflammation
Optical Laser Interferometry
- Measures: axial length, corneal surface curvature, anterior chamber depth, horizontal visible iris diameter
- Uses 780µm infrared light (8x resolution of 10 MHz A-scan)
- Eliminates operator skill level
Cataract Terminology
- Phakic - crystalline lens intact
- Aphakic - crystalline lens missing
- Pseudophakic - intraocular lens replaces natural lens
Myopia Management
- Low-dose atropine to slow axial length growth
- Peripheral defocus lenses to blur peripheral vision
- Orthokeratology to flatten cornea
- Contact lenses (e.g., CooperVision, Johnson & Johnson, Orthok, hard contacts worn overnight) and glasses (e.g., Essilor, Hoya)
Potential Acuity Testing
- Predicts patient's visual acuity after cataract surgery
- Two methods:
- Potential Acuity Meter (PAM): projects Snellen chart via beam of light (0.1 mm aperture)
- Images passed through gaps in the cataract
- Potential Acuity Pinhole (PAP): projects directly onto retina
- 1.0 mm aperture
- Bright light on reading card, use a pinhole
- Potential Acuity Meter (PAM): projects Snellen chart via beam of light (0.1 mm aperture)
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Description
Test your knowledge on the principles of ophthalmic ultrasound in this quiz, covering both A-scan and B-scan techniques. Learn about the wavelengths, frequencies, and applications in diagnosing eye conditions. Ideal for medical students and ophthalmology professionals.
