CPOA Diagnostic Testing 2 — Questions and Answers
Question 1: Which instrument measures intraocular pressure by applanating a small area of the cornea?
- Goldmann applanation tonometer (Correct answer)
- Schiotz tonometer
- Non-contact tonometer
- Perkins tonometer
Correct answer: Goldmann applanation tonometer
The Goldmann applanation tonometer is the gold standard for measuring IOP by flattening a 3.06 mm diameter area of the cornea.
Question 2: During a visual field test using automated perimetry, a 'fixation loss' means the patient:
- Looked away from the fixation target (Correct answer)
- Pressed the response button too slowly
- Had a scotoma in the periphery
- Failed to understand the test instructions
Correct answer: Looked away from the fixation target
Fixation loss occurs when the patient looks away from the fixation target, causing the instrument to detect a response in the known blind spot location.
Question 3: What does the 'cup-to-disc ratio' (C/D ratio) assess when evaluating the optic nerve?
- The proportion of the optic cup diameter to the optic disc diameter (Correct answer)
- The ratio of nerve fiber layer thickness to disc size
- The ratio of retinal vessels entering the disc
- The comparison of right eye disc to left eye disc size
Correct answer: The proportion of the optic cup diameter to the optic disc diameter
The C/D ratio compares the diameter of the central cup to the total diameter of the optic disc, with larger ratios potentially indicating glaucoma.
Question 4: A corneal topography map uses colors to represent corneal curvature; warmer colors (red/orange) typically indicate:
- Steeper curvature with shorter radius (Correct answer)
- Flatter curvature with longer radius
- Normal average curvature
- Irregular astigmatism zones
Correct answer: Steeper curvature with shorter radius
On standard topography maps, warm colors (red, orange) represent steeper corneal areas, while cool colors (blue, green) represent flatter areas.
Question 5: When performing a cover-uncover test, the uncovered eye is observed to detect:
- A tropia (manifest deviation) (Correct answer)
- A phoria (latent deviation)
- Amblyopia
- Accommodation lag
Correct answer: A tropia (manifest deviation)
During the cover-uncover test, movement of the uncovered eye reveals a manifest strabismus (tropia), while the alternate cover test reveals phorias.
Question 6: Pachymetry is used to measure:
- Corneal thickness (Correct answer)
- Anterior chamber depth
- Axial length of the eye
- Pupil diameter
Correct answer: Corneal thickness
Pachymetry measures corneal thickness, which is important for glaucoma risk assessment and pre-refractive surgery evaluation.
Question 7: In retinal photography, a red-free (green) filter is used primarily to:
- Enhance visualization of the nerve fiber layer and blood vessels (Correct answer)
- Reduce glare from the cornea
- Improve visualization of choroidal detail
- Highlight drusen in macular degeneration
Correct answer: Enhance visualization of the nerve fiber layer and blood vessels
Red-free filters block red wavelengths and enhance contrast of the retinal nerve fiber layer, blood vessels, and hemorrhages against the background.
CPOA Diagnostic Testing 2
Which instrument measures intraocular pressure by applanating a small area of the cornea?