Equipment Troubleshooting in the Ophthalmic Office
Ophthalmic diagnostic equipment must function reliably to produce accurate clinical data. As a CPOA, you will encounter equipment malfunctions and must know how to identify common problems, attempt basic fixes, and determine when to escalate to a service technician. Clinically invalid data -- from a misaligned tonometer, a poorly positioned OCT scan, or a corneal artifact in a visual field -- can lead to diagnostic errors and inappropriate treatment changes.
General Troubleshooting Principles
- Always start with the simplest causes: Is it plugged in? Turned on? Are connections secure?
- Consult the manufacturer's manual for error codes and recommended solutions
- Document equipment issues and service dates in a maintenance log
- Never attempt repairs beyond your training -- contact the service technician for significant malfunctions
- Keep calibration records current; many regulatory bodies require periodic documentation of calibration
Goldmann Applanation Tonometer (GAT)
Common problems and solutions:
| Problem | Likely Cause | Solution |
|---|
| Mires appear unequal in size or distorted | Prism not seated correctly; prism cracked or dirty | Reseat prism; clean with approved solution; inspect for cracks |
| Mires don't line up even with proper pressure | Prism rotated from 0 axis; incorrect fluorescein concentration | Verify prism is at 0 (or 43 for significant astigmatism); use fresh fluorescein; check cobalt filter |
| Readings inconsistent between operator and physician | Technique difference; patient squeezing or breath-holding | Coach patient to breathe normally; avoid forceful palpebral closure during measurement |
| Calibration check fails | Tonometer spring deformed or calibration off | Run calibration verification weight checks; send for service if fails |
💡 Clinical Tip: The Goldmann tonometer should be checked for calibration at the beginning of each clinic day using the three-position calibration check described in the manual (typically at 0, 2, and 6 mmHg positions). Log results. A tonometer that fails calibration must not be used clinically until serviced.
Automated Visual Field Analyzer (Humphrey Field Analyzer)
| Problem | Likely Cause | Solution |
|---|
| High false-positive rate | Patient pressing too eagerly; "trigger-happy" | Reinforce instructions; some FP rate is normal (up to 20%) |
| High false-negative rate | Patient fatigue; inattention; real field loss | Check fixation losses and test reliability; consider retesting on a different day |
| Excessive fixation losses | Poor fixation; head movement; eye movement during test | Reposition patient; use eye patch on fellow eye; remind to fixate on central target; use fixation monitor (SLO) |
| Test not starting / program error | Incorrect patient data entered; software error | Verify patient parameters; restart software; contact service if persistent |
| Cloverleaf pattern defect | Fatigue artifact (patient stops attending late in test) | Consider retesting; shorten test duration |
OCT (Optical Coherence Tomography)
| Problem | Likely Cause | Solution |
|---|
| Poor signal strength / faint scan | Inadequate dilation; media opacity (cataract, corneal scar); uncorrected refractive error in machine settings | Maximize dilation; enter correct sphere in machine; adjust focus |
| Off-center scan (fovea not centered) | Poor fixation; incorrect fixation target selection | Use fixation target appropriate for that eye; switch to external fixation for poor fixation eyes |
| Layer segmentation errors | Media opacity; high myopia; epiretinal membrane distorting layers | Flag for physician review; manual correction of segmentation lines if available |
| Motion artifact (stepping/banding) | Patient movement or blinking | Retake scan; coach patient to blink between scans, not during; use faster scan protocols |
Slit Lamp
| Problem | Likely Cause | Solution |
|---|
| Dim illumination | Bulb aging; voltage issue | Replace bulb; check voltage; verify rheostat is turned up |
| Uneven or asymmetric illumination | Bulb misaligned; mirror dirty or tilted | Clean internal mirror; re-center bulb; consult service |
| Fogging of eyepiece | Room condensation; eyepiece dirty | Clean eyepiece with lens cloth; avoid breathing directly on eyepieces |
| Joystick hard to move / stiff | Debris in track; joystick needs lubrication | Clean joystick base; service if stiff |
Autorefractor / Keratometer
| Problem | Likely Cause | Solution |
|---|
| Unreliable readings / high variability | Dry eye; accommodative fluctuation; media opacity | Instill artificial tears before measuring; take multiple readings; recheck manually |
| Error message on keratometry | Tear film irregularity; corneal irregularity; misalignment | Blink to refresh tear film; re-center instrument; consider manual keratometry for irregular corneas |
| Device won't align | Patient not fixating; eye too close or far | Coach fixation; adjust working distance; try other eye first if patient is struggling |
⚠️ Common Mistake: Accepting a single autorefractor reading without checking reliability indicators is poor practice. Most modern autorefractors give a confidence index or standard deviation across readings. If variability is high, re-measure, check for dry eye, and note potential unreliability in the chart.
Key Takeaways
- Always start with simple causes (connections, power, calibration) before assuming complex failure
- Tonometer calibration should be verified daily; a failed calibration means the instrument cannot be used clinically
- Visual field reliability indices (fixation losses, false positives, false negatives) determine test validity
- OCT signal strength, scan centering, and segmentation quality must be verified before accepting results
- Document all equipment issues and service dates in a maintenance log
- Never attempt repairs beyond your scope; contact the service technician for significant malfunctions