Equipment Maintenance and Repair

Equipment Maintenance and Repair is 2% of the COA exam. Nearly every number in the chart comes from an instrument, and instruments rarely fail all at once: lamps dim, calibrations drift, and optics collect dust. A mis-calibrated instrument quietly corrupts every measurement taken with it.

Two jobs, two products — cleaning optics and disinfecting the surfaces patients touch are separate tasks, done with different products on different parts of the same instrument.

Slit lamp biomicroscope — the anterior-segment workhorse. Know the illumination arms, magnification changer, and how to focus and center for the physician.

Know the parts — binocular eyepieces and a magnification changer; an illumination arm whose slit width, height, and angle can be changed; filters, including cobalt blue (used with fluorescein for applanation mires and epithelial defects) and red-free (green); a joystick for focus and position; and the chin rest and forehead band.

Set it up in order — first focus each eyepiece for your own eyes, using the focusing rod the manufacturer supplies. Start each eyepiece at its plus end and turn until the rod's surface just turns sharp, so your own focusing stays relaxed. Then slide the eyepieces together or apart until the two images merge. Last, once the patient is in place, adjust the chin rest height so the outer corner of the patient's eye sits level with the mark on the headrest post.

Your own settings — eyepiece settings are personal. Working with someone else's leaves the microscope focused on a slightly different plane from the slit beam, which matters most for photography and applanation.

Leave it ready — dust cover on when idle, joystick centered, and the chin rest and forehead band disinfected for the next patient.

Coated optics — anti-reflective coatings scratch easily. Blow or brush away loose grit before anything touches the glass, then wipe gently with lens tissue and the manufacturer's approved cleaner. Never household glass cleaner, solvents, paper towels, or dry gauze.

Contact points — disinfect the chin rest, forehead band, handles, and joystick between patients, leaving the surface wet for the product's full contact time and keeping the disinfectant off the optics.

Diagnostic lenses — a handheld lens that never touches the eye, such as a 78 D or 90 D lens, is cleaned. A lens that touches the cornea, such as a gonioscopy lens, is cleaned, disinfected, rinsed, and dried between patients. Coated diagnostic lenses are never put through an autoclave; heat ruins the coatings.

Tonometer tips — disinfected between patients by a timed soak, rinse, and dry per CDC and manufacturer protocol, or replaced with disposable tips.

Phoropter — dust cover on when idle and lenses cleaned on a schedule; the forehead rest is disinfected between patients like any other contact point. Dust and skin oil on its small lenses degrade every refraction.

Changing a bulb — let it cool first. Handle a halogen bulb by its base or with tissue, never touching the glass, because skin oils make it fail early. Use exactly the specified voltage and wattage: a stronger bulb can overheat the instrument and its wiring. Then check the light before the next patient.

A dim, yellowish beam with a new, correct bulb — another bulb will not fix it. Make sure the brightness control is turned up, then suspect the power supply, such as a tired battery pack, a failing transformer, or a poor connection, and report it.

Troubleshoot simple to complex — the outlet (test it with a device you know works), the switch, the fuse, the bulb and its seating, the cleanliness of the optics, and only then a service call.

Fuses — a fuse is a safety device. Unplug the instrument and replace the fuse with exactly the type and rating printed at the holder. A fuse that blows a second time means an internal fault, and the instrument goes out for repair.

Grounding — plug each instrument into a properly grounded outlet. No three-to-two prong adapters, no cut ground pins, and no chains of power strips or extension cords across a lane.

When something is wrong — a frayed cord, a hot plug, a tingle, a burning smell, or erratic behavior means take the instrument out of service, tag it, and report it. Never keep using questionable equipment on patients, and leave electrical repairs to qualified service staff.

Daily care — dust covers on, chin rests disinfected between patients, bulbs and batteries stocked, calibration checks logged.

Calibration checks — lensometer: reads plano (zero) with no lens in place. Keratometer: the steel balls read their known values. Goldmann tonometer: the check bar at its standard settings (for example 0, 2, and 6), on schedule. A tonometer out of tolerance comes out of service, because every glaucoma decision rides on it.

When a check fails — nobody knows when the error began, so every reading since the last passing check is suspect. Take the instrument out of service, document it, and tell the physician, who decides which readings need repeating. Never apply a private mental correction.

The maintenance log — date, the check performed, the result, the action taken, and the initials of whoever did it. A log proves checks happened and shows drift over time.

After a repair — check the instrument before the first patient, not at the next scheduled service, including the tonometer's calibration if it was removed from the slit lamp.

Lane geometry — a 20/20 letter is 20/20 only at the distance it was scaled for. In a mirrored lane the testing distance is the whole light path, chart to mirror plus mirror to patient. Moving a chart, mirror, or chair means recalibrating.

Level the phoropter — a tilted phoropter puts every cylinder axis off by the amount of the tilt.

Be ready to name each instrument's calibration check, separate cleaning optics from disinfecting contact points, set up a slit lamp, change a bulb safely, say what to do with a frayed cord or erratic instrument, list what a maintenance log records, and explain how autoclave cycles are verified with chemical indicators and spore tests.