Abstract
Purpose :
Heterophoria is routinely measured in a typical binocular vision assessment. There are different ways to assess phoria and several studies have quantified the accuracy and precision of these methods. Unfortunately, most of the methods are subjective and have their own limitations. The aim of the current study is to quantify a commercially available objective way to assess phoria, the Neurolens measurement device (nMD), and compare its inter-examiner repeatability with that of prism alternating cover test and the Von Graefe method.
Methods :
90 young adults, aged between 18-40 years, with normal binocular vision were enrolled into the study. Two experienced optometrists assessed phoria on each subject using three methods: Von Graefe (VG), prism alternating cover test (PCT) and nMD. All the measurements were done at distance (6m) and near (40cm). All the tests were performed in a similar way by both the examiners in a randomized order.
Results :
The nMD (dist: 0.69 ± 0.77PD; near: 1.00 ± 0.98PD) has the smallest mean absolute difference at both distance and near compared to VG (dist: 3.28 ± 3.18PD; near: 4.48 ± 3.99PD) and PCT (dist: 1.50 ± 2.36PD; near: 4.05 ± 3.69PD). Bland Altmann Plots showed that the phoria measurements from nMD exhibited significantly less variability when compared with VG and PCT. Overall, using intraclass correlations, high agreement was noted between the two examiners with the nMD (r_distance: 0.91; r_near: 0.95) compared to VG (r_dist: 0.50; r_near: 0.72) and PCT (r_dist: 0.65; r_near: 0.73).
Conclusions :
The Neurolens measurement device (nMD) provides precise phoria measurements and has the highest inter-examiner repeatability when compared to traditional VG and PCT methods. This is useful information for optometrists considering adding objective binocular vision measurements to their particular mode of practice.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.