Purpose: To assess the effect of examiner handedness on intraocular pressure (IOP) readings using the Tono-Pen XL in eyes without corneal pathology or previous ocular surgeries.
Patients and methods: Patients 18 years of age or older were included in this prospective study. Participants who had a history of corneal conditions or other characteristics that would prevent reliable IOP measurements were excluded. Five experienced examiners, 2 right-hand dominant and 3 left-hand dominant, took bilateral IOP measurements with a Tono-Pen XL. Each participant was tested by 2 examiners, 1 left-handed and 1 right-handed, in a random order. The time between each examiner's measurements was 15 minutes. A paired t test was used to compare IOP differences between "near" (right eye for right-hand or left eye for left-hand dominant examiner) and "far" (right eye by left-hand or left eye by right-hand dominant examiner) measurements for each eye.
Results: Forty-six participants with a mean age of 33.8 years (±12.8) were enrolled. No significant difference in IOP between near and far eyes was found (IOP difference=IOPfar-IOPnear=-0.11 [±2.74] mm Hg; P=0.70). Right-hand dominant examiners consistently measured significantly higher IOP (0.83±2.03 mm Hg; P=0.008) compared with left-hand dominant examiners, regardless of the relative position of the eye with respect to the examiner.
Conclusions: The results suggest that IOP readings are not influenced by the positioning of the patient relative to the dominant hand of the examiner.