Vision and Ophthalmology Diagnostic Testing and Equipment 2 — Questions and Answers
Question 1: Electroretinography (ERG) measures the electrical response of which cells in the retina?
- Ganglion cells only
- Photoreceptors and bipolar cells (a-wave and b-wave) (Correct answer)
- Müller cells only
- Retinal pigment epithelium only
Correct answer: Photoreceptors and bipolar cells (a-wave and b-wave)
The full-field ERG records mass electrical responses: the a-wave primarily reflects photoreceptor function and the b-wave reflects bipolar/Müller cell activity.
Question 2: The Humphrey visual field analyzer uses which method to test the visual field?
- Kinetic perimetry (moving targets)
- Static automated perimetry (stationary targets at fixed locations) (Correct answer)
- Confrontation fields
- Amsler grid
Correct answer: Static automated perimetry (stationary targets at fixed locations)
The Humphrey Field Analyzer uses static automated perimetry, presenting stationary light stimuli at predetermined locations and varying intensity to determine threshold sensitivity.
Question 3: Specular microscopy is used to evaluate which ocular structure?
- Trabecular meshwork
- Corneal endothelium (endothelial cell count and morphology) (Correct answer)
- Retinal nerve fiber layer
- Lens cortex
Correct answer: Corneal endothelium (endothelial cell count and morphology)
Specular microscopy images the corneal endothelium, providing cell count (cells/mm²), cell size (polymegethism), and shape variation (pleomorphism).
Question 4: Which imaging modality is the gold standard for evaluating the optic nerve fiber layer in glaucoma?
- Fundus photography
- Optical coherence tomography (OCT) (Correct answer)
- Fluorescein angiography
- B-scan ultrasonography
Correct answer: Optical coherence tomography (OCT)
Spectral-domain OCT provides quantitative measurements of retinal nerve fiber layer (RNFL) thickness, which correlates with ganglion cell loss in glaucoma.
Question 5: The pupillary light reflex is evaluated clinically using which test for afferent pathway defects?
- Worth 4-dot test
- Swinging flashlight test (RAPD) (Correct answer)
- Confrontation fields
- Color vision testing
Correct answer: Swinging flashlight test (RAPD)
The swinging flashlight test detects a relative afferent pupillary defect (RAPD/Marcus Gunn pupil), indicating unilateral optic nerve or extensive retinal disease.
Question 6: Pachymetry measures which parameter of the cornea?
- Radius of curvature
- Thickness (Correct answer)
- Endothelial cell density
- Transmittance
Correct answer: Thickness
Pachymetry measures corneal thickness, which is important for IOP interpretation (thin corneas give falsely low readings) and LASIK candidacy screening.
Vision and Ophthalmology Diagnostic Testing and Equipment 2
Electroretinography (ERG) measures the electrical response of which cells in the retina?