COT Ophthalmic Imaging and Photography 3 — Questions and Answers
Question 1: Fundus autofluorescence (FAF) imaging relies on the natural fluorescence of which substance in the retinal pigment epithelium?
- Melanin
- Lipofuscin (Correct answer)
- Rhodopsin
- Xanthophyll
Correct answer: Lipofuscin
Lipofuscin, a byproduct of incomplete photoreceptor outer segment digestion, accumulates in the RPE and is the primary source of fundus autofluorescence.
Question 2: When performing corneal topography, the Placido disc system measures corneal curvature by analyzing:
- Purkinje reflections from the lens
- Reflected concentric ring images from the corneal surface (Correct answer)
- Scattered light from the stroma
- Interference fringes from the tear film
Correct answer: Reflected concentric ring images from the corneal surface
Placido-based topographers project concentric rings onto the cornea and calculate curvature from the spacing and shape of their reflections.
Question 3: A cotton-wool spot on fundus photography corresponds pathologically to:
- Hard exudate from lipid deposition
- Focal nerve fiber layer infarction (Correct answer)
- Choroidal neovascularization
- Drusen coalescence
Correct answer: Focal nerve fiber layer infarction
Cotton-wool spots represent focal ischemic infarcts of the nerve fiber layer causing axoplasmic flow stasis and cytoid bodies.
Question 4: Which OCT scan pattern provides the most comprehensive macular thickness map for detecting early diabetic macular edema?
- Single horizontal line scan
- Radial spoke pattern
- Macular cube (raster) scan (Correct answer)
- Circle scan around the optic disc
Correct answer: Macular cube (raster) scan
A macular cube (dense raster) scan samples the entire macular area with multiple parallel B-scans, providing a full thickness map.
Question 5: The cobalt blue filter on a slit lamp is used in conjunction with fluorescein dye primarily to evaluate:
- Lens clarity
- Corneal epithelial defects (Correct answer)
- Vitreous opacities
- Optic nerve cupping
Correct answer: Corneal epithelial defects
Cobalt blue light excites sodium fluorescein, which pools in corneal epithelial defects and fluoresces green, revealing the defect's extent.
Question 6: In Heidelberg Retinal Tomography (HRT), the reference plane used to calculate neuroretinal rim area is set at:
- The vitreoretinal interface
- 50 μm posterior to the temporal disc margin (Correct answer)
- The Bruch's membrane opening
- The lamina cribrosa surface
Correct answer: 50 μm posterior to the temporal disc margin
HRT uses a reference plane set 50 μm posterior to the mean height of the papillomacular bundle to calculate disc topography parameters.
Question 7: A photograph of the optic disc shows a cup-to-disc ratio of 0.8. This finding is most clinically significant when combined with:
- Myopia greater than −1.00 D
- Superior or inferior neuroretinal rim thinning (Correct answer)
- A positive history of cataracts
- Hyperopic refraction
Correct answer: Superior or inferior neuroretinal rim thinning
A large C/D ratio alone is not diagnostic; superior or inferior rim thinning (ISNT rule violation) increases suspicion for glaucomatous damage.
COT Ophthalmic Imaging and Photography 3
Fundus autofluorescence (FAF) imaging relies on the natural fluorescence of which substance in the retinal pigment epithelium?