Paraoptometric professionals are frequently responsible for the daily cleaning, disinfection, calibration verification, and basic maintenance of clinical instruments. Properly maintained instruments produce accurate measurements, protect patient safety through infection control, and remain in service longer—protecting the practice's significant investment in diagnostic equipment. The CPO and CPOA exams test your knowledge of maintenance procedures for the instruments used in optometric practice.
Why Instrument Maintenance Matters
Measurement Accuracy
An uncalibrated tonometer, a dusty lensometer, or a misaligned autorefractor produces incorrect data that drives incorrect clinical decisions.
Infection Control
Improperly disinfected instruments—especially tonometer tips and slit lamp contact lenses—can transmit pathogens between patients.
Equipment Longevity
Regular cleaning prevents corrosion, dust accumulation in optics, and mechanical wear. Proper care extends instrument life by years.
Maintenance Guide by Instrument
- Slit Lamp Biomicroscope — Wipe chin rest and forehead rest with 70% isopropyl between each patient, Clean eyepieces with optical tissue—never paper towel, Cover with dust cover when not in use — Check all control dials and locks for smooth function, Inspect illumination system and slit aperture for dust — Professional optical cleaning of internal elements annually, Bulb replacement per manufacturer schedule
- Goldmann Applanation Tonometer — Disinfect tonometer tip after each use (H2O2 or 1:10 bleach, 10-min soak; rinse thoroughly), Wipe tonometer arm and control with disinfectant wipe — Check calibration with calibration bar (0 g, 1 g, 2 g)—should read 0, 10, 20 mmHg respectively — Return to manufacturer or service center if calibration fails, Replace tip prism if scratched or pitted (affects accuracy)
- Lensometer (Manual) — Clean eyepiece with optical cleaner, Clean lens stop with soft cloth, Verify zero with no lens present (standard axis and power) — Verify calibration with a known-power trial lens, Clean all external surfaces — Bulb replacement for illuminated models, Professional calibration annually
- Autorefractor / Keratometer — Wipe chin rest and forehead rest with disinfectant between patients, Clean external optical window per manufacturer instructions, Power cycle if readings are inconsistent — Verify calibration using the test eye / model eye provided by manufacturer, Clean any external surfaces and inspect cords/cables — Software updates per manufacturer, Professional calibration check annually
- Non-Contact Tonometer (NCT) — Disinfect chin rest and forehead rest between patients, Clean external optical elements per manufacturer (air puff nozzle area), Verify IOP standard reads within range using test measurement if available — Wipe instrument body and controls, Check air puff mechanism for obstructions — Annual calibration verification by manufacturer or service tech
- Phoropter — Clean chin rest and forehead rest with disinfectant wipe, Verify 0.00 reads correctly (lens position check) — Clean eyepiece lenses with appropriate optical cleaner, Check all dials and wells for smooth movement — Annual professional calibration verification, Service if lenses are stuck, misaligned, or contaminated
Calibration Principles
Calibration verification ensures instruments produce accurate measurements. Key principles:
- Use the manufacturer's calibration standard — Each instrument comes with a test object, model eye, or calibration weight. Use only this to verify—improvised standards introduce error.
- Document calibration results — Record the date, result (pass/fail), and who performed the check. A maintenance log demonstrates regulatory compliance.
- Remove from service if it fails — A tonometer or lensometer that fails calibration must be taken out of service until corrected—continuing to use it risks patient harm.
- Know when to call for service — Paraoptometrics perform routine checks; professional biomedical engineers or manufacturer technicians perform actual recalibration and internal adjustments.