FREE CPO Ophthalmic Instrument Maintenance and Calibration Questions and Answers

Question 1

How is the calibration of a Goldmann applanation tonometer checked?

Accepted Answer

Using a standardized calibration bar at the 0, 2, and 6 positions

Answer

A special calibration bar is used to check the accuracy of a Goldmann tonometer at three specific settings: 0, 2, and 6. This corresponds to 0, 20, and 60 mm Hg. This check should be performed regularly to ensure accurate intraocular pressure measurements.

Question 2

What is the first and most critical step before using a manual lensometer to ensure an accurate reading?

Accepted Answer

Focusing the eyepiece

Answer

Before measuring any lens, the operator must focus the eyepiece for their own eye. This is done by turning the eyepiece counter-clockwise, then slowly turning it clockwise until the reticle (crosshairs) first becomes sharp and clear. An improperly focused eyepiece is a primary source of error in lensometry.

Question 3

When changing the bulb in a slit lamp or projector, what is the most important precaution to take with the new bulb?

Accepted Answer

Avoid touching the glass portion of the bulb with bare hands

Answer

The oils from human skin can create hot spots on the glass surface of a halogen bulb when it heats up. These hot spots can cause the bulb to fail prematurely. Therefore, it is crucial to handle the new bulb with a clean cloth or gloves, avoiding direct contact with bare fingers.

Question 4

Which solution is generally NOT recommended for cleaning the lens surfaces of a phoropter (manual refractor)?

Accepted Answer

Alcohol

Answer

Alcohol-based cleaners can be too harsh and may damage the anti-reflective coatings on the phoropter lenses over time. It is best to use a manufacturer-approved lens cleaner or a gentle solution like diluted isopropyl alcohol (if approved) and a soft, lint-free cloth.

Question 5

To ensure accurate readings from a keratometer, what part of the instrument must be kept clean and unobstructed?

Accepted Answer

The mires

Answer

The keratometer measures corneal curvature by analyzing the reflection of a circular pattern, known as mires, off the patient's cornea. If the mires on the instrument are dirty or smudged, the reflection will be distorted, leading to inaccurate measurements of corneal power and astigmatism.

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FREE CPO Ophthalmic Instrument Maintenance and Calibration Questions and Answers