Free CPO Ophthalmic Instrument Maintenance and Calibration Questions and Answers 1 — Questions and Answers
Question 1: How is the calibration of a Goldmann applanation tonometer checked?
- By comparing its reading to an electronic tonometer
- Using a standardized calibration bar at the 0, 2, and 6 positions (Correct answer)
- By measuring the pressure of a known saline-filled model eye
- Sending it to the manufacturer for annual service
Correct answer: Using a standardized calibration bar at the 0, 2, and 6 positions
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?
- Wiping the lens stop with an alcohol pad
- Turning on the marking pins
- Focusing the eyepiece (Correct answer)
- Setting the power wheel to zero
Correct answer: Focusing the eyepiece
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?
- Ensure the power is on to check for a good connection
- Wipe the bulb with an alcohol prep pad before installation
- Avoid touching the glass portion of the bulb with bare hands (Correct answer)
- Tighten the bulb as much as possible to secure it
Correct answer: Avoid touching the glass portion of the bulb with bare hands
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)?
- Alcohol (Correct answer)
- Approved ophthalmic lens cleaner
- Distilled water
- A soft, lint-free microfiber cloth
Correct answer: Alcohol
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?
- The joystick base
- The forehead rest
- The occluder
- The mires (Correct answer)
Correct answer: The mires
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.
Question 6: What is a standard daily maintenance procedure for automated instruments like an autorefractor or non-contact tonometer?
- Disassembling the internal optics for cleaning
- Recalibrating the measurement prism
- Wiping down the chinrest and forehead rest with a disinfectant (Correct answer)
- Updating the device's software
Correct answer: Wiping down the chinrest and forehead rest with a disinfectant
Because patients make direct contact with the chinrest and forehead rest, these surfaces must be cleaned and disinfected between every patient. This is a critical infection control measure and a standard part of daily instrument maintenance to ensure patient safety and hygiene.
Free CPO Ophthalmic Instrument Maintenance and Calibration Questions and Answers 1
How is the calibration of a Goldmann applanation tonometer checked?