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Falsely high rebound tonometry
Brooke Saffren1, Jade M Price2, Qiang Ed Zhang3
1Pediatric Ophthalmology and Ocular Genetics, Wills Eye Hospital, Philadelphia, Pennsylvania; Philadelphia College of Osteopathic Medicine, Philadelphia, Pennsylvania.
Insights
Rebound tonometry (RBT) may overestimate intraocular pressure (IOP) in children, showing a difference of 6 mm Hg or more compared to applanation tonometry (AT). Factors like persistent fetal vasculature and larger corneal diameter increase this discrepancy.
Area of Science:
- Ophthalmology
- Pediatric Medicine
- Medical Device Technology
Background:
- Rebound tonometry (RBT) is an alternative for measuring intraocular pressure (IOP) in pediatric patients who cannot tolerate applanation tonometry (AT).
- RBT measurements typically exceed AT readings by 2-3 mm Hg.
- A significant discrepancy (≥6 mm Hg) between RBT and AT readings has been observed in some children.
Purpose of the Study:
- To identify demographic and ocular characteristics associated with a significant artifactuous discrepancy between RBT and AT intraocular pressure measurements in pediatric patients.
Main Methods:
- Retrospective review of medical records for pediatric patients with IOP measured by RBT followed by AT within a 6-month period.
- Exclusion criteria included intervening surgery or changes in medical management between measurements.
- Analysis focused on identifying predictors of a greater than or equal to 6 mm Hg difference between RBT and AT readings.
Main Results:
- 18.5% of eyes with normal IOP (≤24 mm Hg) showed a ≥6 mm Hg RBT-AT difference, with risk factors including persistent fetal vasculature (PFV), increased corneal diameter, and higher initial RBT (>20).
- 77% of eyes with elevated IOP (>24 mm Hg) exhibited a ≥6 mm Hg RBT-AT difference, with larger corneal diameter being the sole predictor.
- Corneal opacity or iris abnormalities were associated with a lower likelihood of significant RBT-AT difference in eyes with elevated IOP.
Conclusions:
- A significant discrepancy (≥6 mm Hg) between RBT and AT IOP measurements can occur in pediatric patients.
- Caution is advised when interpreting RBT values in children with PFV, increased corneal diameter, and high initial RBT readings.
Background:
Rebound tonometry (RBT) can be used to measure intraocular pressure (IOP) in children unable to tolerate measurement with applanation tonometry (AT) while awake. RBT readings are often 2-3 mm Hg higher than AT. We have experienced children with a repeatedly higher difference between RBT and AT measurements (≥6 mm Hg). The purpose of this study was to identify demographic and ocular characteristics that contribute to this artifactuous discrepancy.
Methods:
The medical records of pediatric patients with IOP measured by RBT followed by AT within 6 months without intervening surgery or change in medical management were retrospectively reviewed to identify potential predictors of greater difference between RBT and AT readings.
Results:
A total of 123 eyes of 65 patients were included. In patients with normal IOP (≤24 mm Hg), 18.5% had a ≥6 mm Hg difference between RBT and AT, with RBT being higher. Risk factors for this included presence of persistent fetal vasculature (PFV), increased corneal diameter, and higher initial RBT value (>20). In patients with elevated IOP (>24 mm Hg), 77% had ≥6 mm Hg difference, with larger corneal diameter being the sole predictor. Eyes were less likely to have significant RBT-AT difference if there was corneal opacity or iris abnormalities in eyes with elevated IOP (>24 mm Hg).
Conclusions:
In some children, RBT readings are ≥ 6 mm Hg higher than AT readings. Caution should be taken when interpreting RBT values in patients with PFV, increased corneal diameter, and higher initial RBT values.
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