COT - Certified Ophthalmic Technician Ophthalmic Imaging and Photography Questions and Answers — Questions and Answers
Question 1: A patient undergoing fluorescein angiography begins to show dye filling the retinal arterioles approximately one to two seconds after the choroidal flush. Which phase of the angiogram is occurring?
- Choroidal Phase
- Arterial Phase (Correct answer)
- Venous Phase
- Late Phase
Correct answer: Arterial Phase
The arterial phase of a fluorescein angiogram is characterized by the filling of the retinal arterioles, which typically happens 1-2 seconds after the initial choroidal flush. The choroidal phase is the very first appearance of the dye in the choroid. The venous phase follows the arterial phase, showing the veins filling. The late phase occurs several minutes later as the dye is eliminated.
Question 2: When performing fundus photography on a patient with small pupils, a bright, orange-colored crescent appears at the edge of the image. What is the most likely cause of this artifact?
- Dust on the camera lens
- Corneal opacification
- Incorrect camera-to-eye distance
- Illumination beam reflecting off the iris (Correct answer)
Correct answer: Illumination beam reflecting off the iris
An orange or bright crescent at the margin of a fundus photograph is a common artifact caused by the camera's illumination light hitting and reflecting off the edge of the iris, especially in cases of poor pupillary dilation. To correct this, the camera's joystick should be moved away from the crescent to better center the light beam through the pupil.
Question 3: A technician is reviewing a corneal topography map to assist in fitting a patient for rigid gas-permeable (RGP) contact lenses. The axial map displays a localized area with predominantly red and orange colors, surrounded by green. How should the technician interpret this finding?
- An area of corneal thinning
- A flat region of the cornea
- A steep area of the cornea (Correct answer)
- An area of corneal scarring
Correct answer: A steep area of the cornea
On a standard axial corneal topography map, warmer colors like red and orange represent steeper areas of the cornea, while cooler colors like blue and green indicate flatter regions. This information is crucial for selecting the appropriate base curve for a contact lens.
Question 4: Which of the following imaging modalities provides a cross-sectional, high-resolution view of the retinal layers, making it invaluable for detecting and monitoring conditions like macular edema and vitreomacular traction?
- Fundus Autofluorescence (FAF)
- B-scan Ultrasonography
- Optical Coherence Tomography (OCT) (Correct answer)
- Slit-lamp Photography
Correct answer: Optical Coherence Tomography (OCT)
Optical Coherence Tomography (OCT) is a non-invasive imaging test that uses light waves to take cross-section pictures of the retina. It allows for the visualization of each of the retina’s distinct layers, which is essential for the diagnosis and management of retinal diseases like macular edema, macular holes, and epiretinal membranes.
Question 5: While acquiring an Optical Coherence Tomography (OCT) scan of the macula, the technician notes a low Signal Strength (SS) value and observes significant motion artifacts and poor delineation of the retinal layers. Which action is most appropriate to improve the scan quality?
- Increase the room lighting to constrict the pupil.
- Proceed with the scan as is, since the software will correct it.
- Re-align the patient, coach them to fixate steadily, and re-scan. (Correct answer)
- Switch to a fundus photography camera instead.
Correct answer: Re-align the patient, coach them to fixate steadily, and re-scan.
Poor OCT image quality, indicated by low signal strength and artifacts, is often due to factors like poor patient alignment, blinking, or unsteady fixation. The best initial step is to reinstruct and realign the patient to ensure their eye is properly positioned and stable before recapturing the image. Scan quality is critical for accurate interpretation and diagnosis.
Question 6: During fundus photography, the technician notices a persistent, well-defined dark spot that appears in the same location on every image, regardless of patient position or focus. This artifact is most likely caused by:
- A floater in the patient's vitreous
- A smudge or debris on the camera's internal lens or sensor (Correct answer)
- An eyelash in the optical pathway
- A corneal foreign body
Correct answer: A smudge or debris on the camera's internal lens or sensor
An artifact that remains fixed in the same location across multiple photographs of different eyes or different areas of the same eye is indicative of an issue with the camera system itself, such as dust or a smudge on one of the lenses or the sensor. Patient-related artifacts like floaters, eyelashes, or corneal issues would move or change as the patient's eye moves.
COT - Certified Ophthalmic Technician Ophthalmic Imaging and Photography Questions and Answers
A patient undergoing fluorescein angiography begins to show dye filling the retinal arterioles approximately one to two seconds after the choroidal flush.
Which phase of the angiogram is occurring?