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The non-contact ("air puff") tonometer: variability and corneal staining
American Journal of Optometry and Physiological Optics
|January 1, 1975
Summary
Non-contact tonometry (NCT) may cause minor corneal epithelial defects. Initially higher NCT readings are likely due to patient apprehension, not aqueous humor massage, with lower readings indicating acceptance.
Area of Science:
- Ophthalmology
- Optometry
- Biomedical Engineering
Background:
- Intraocular pressure (IOP) measurement is crucial for diagnosing glaucoma.
- Non-contact tonometry (NCT) is a common method for IOP assessment.
- Potential corneal trauma and massage effects from repeated NCT use require investigation.
Purpose of the Study:
- To evaluate the risk of corneal trauma from repeated NCT applications.
- To determine if repeated NCT affects intraocular pressure readings through a massage effect.
- To analyze the variability and influencing factors of NCT measurements.
Main Methods:
- Fifteen normal human eyes underwent 150 successive applanations with an NCT.
- Corneal status was assessed using slit lamp examination after fluorescein instillation.
- Intraocular pressure readings were recorded throughout the repeated measurements.
Main Results:
- Minor, superficial corneal epithelial defects were occasionally observed.
- Initial higher IOP readings decreased with successive measurements.
- Variability in NCT readings was approximately ±1-2 mm Hg, potentially linked to the cardiac cycle.
Conclusions:
- Repeated NCT use can cause minimal corneal epithelial defects.
- Decreasing NCT readings are attributed to patient acclimatization, not aqueous humor massage.
- NCT measurement variability is influenced by physiological factors like the cardiac cycle.