COA Ophthalmic Instruments and Procedures 3 — Questions and Answers
Question 1: When performing keratometry, what information is obtained?
- Intraocular pressure in two meridians
- Anterior corneal curvature in the principal meridians (Correct answer)
- Corneal thickness at the apex
- Anterior chamber depth
Correct answer: Anterior corneal curvature in the principal meridians
Keratometry measures the radius of curvature of the anterior cornea in the flattest and steepest meridians.
Question 2: The Amsler grid is specifically used to detect abnormalities in:
- Peripheral visual field
- Central macular function (Correct answer)
- Color vision deficiency
- Contrast sensitivity
Correct answer: Central macular function
The Amsler grid detects metamorphopsia and central scotomas within the central 20 degrees of the visual field.
Question 3: What is the primary diagnostic purpose of fluorescein angiography?
- Measure corneal thickness
- Evaluate retinal and choroidal circulation (Correct answer)
- Determine refractive error
- Assess intraocular pressure
Correct answer: Evaluate retinal and choroidal circulation
Fluorescein angiography documents retinal and choroidal blood flow by imaging intravenous fluorescent dye.
Question 4: Which device is used to calculate intraocular lens power before cataract surgery?
- Keratometer alone
- Optical biometry device (e.g., IOL Master) (Correct answer)
- Slit lamp with pachymeter
- Autorefractor
Correct answer: Optical biometry device (e.g., IOL Master)
Optical biometry devices measure axial length and corneal curvature to calculate the appropriate IOL power.
Question 5: Compared to indirect ophthalmoscopy, the direct ophthalmoscope provides:
- Wider field of view
- Higher magnification of a small fundus area (Correct answer)
- Better view through dense cataracts
- Stereoscopic three-dimensional imaging
Correct answer: Higher magnification of a small fundus area
The direct ophthalmoscope provides approximately 15× magnification but only a small field of the fundus.
Question 6: Corneal topography is most useful for detecting:
- Intraocular pressure distribution
- Irregular corneal surface changes such as keratoconus (Correct answer)
- Retinal thickness changes
- Anterior chamber angle anatomy
Correct answer: Irregular corneal surface changes such as keratoconus
Corneal topography maps the entire corneal surface curvature, revealing irregularities like keratoconus or post-surgical changes.
COA Ophthalmic Instruments and Procedures 3
When performing keratometry, what information is obtained?