Examiner Handedness and the Effects on Intraocular Pressure Readings

Abstract

Purpose : Handedness may affect the technique used to measure intraocular pressure (IOP) using hand-held tonometers, such as the Tono-Pen XL (Reichert Technologies, Depew, NY). It is unknown whether those handedness-driven techniques affect the results. The purpose of our study is to assess the effect of examiner handedness on IOP readings using Tono-Pen XL in healthy individuals.

Methods : Patients 18 years of age or older were recruited for this prospective study. Participants who had a history of corneal conditions that could affect the accuracy of IOP measurements or conditions that would prevent or inhibit 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, one left-handed and one right-handed, in a randomized order. For example, the right-handed first examiner stood on the participant’s right side and took measurements on the right (“near”) eye first, followed by the left (“far”) eye, and the left-handed second examiner did the same order (right then left eye) standing on the left side. If the left-handed examiner was first, then the left eye was examined first by each examiner. The time between each examiner’s measurements was 15 minutes. A paired t-test was used to compare IOP differences between “near” and “far” measurements for each eye.

Results : Forty-six participants with a mean age of 33.8 years (± 12.8) were enrolled. Twenty-six participants (57%) were examined by a right-handed examiner first. IOPs taken from the “near” and “far” sides were not significantly different (IOP Difference = IOP_far – IOP_near = 0.11 mm Hg [±2.74], P=0.70; Table 1). The difference in measurement between eyes was not significant for either right-handed or left-handed examiners. However, right-handed examiners consistently measured IOP higher compared to left-handed examiners by 0.83 mm Hg (± 2.03, P= 0.008), regardless of which eye, near or far (Table 2).

Conclusions : The results suggest that IOP readings are not influenced by the positioning of the patient relative to the dominant hand of the examiner. The mechanism behind the difference is unclear and requires additional study.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Table 1: Difference of IOP taken between the far eye and the near eye.

 

Table 2. Mean Difference of IOP (mmHg, ± standard deviation) taken in each eye and by left- and right-handed examiners.