Objective horizontal heterophoria measurements using a new vision analyzer

Compartir 01/03/2015 Publicaciones Científicas

J. Pujol , R. Borras , I. Claramunt, M. Sanchez , Alfonso Sanchez-Magan, J. C. Ondategui-Parra

DAVALOR Research Center (DRC) Universitat Politècnica de Catalunya, Terrassa, Spain.


To compare the results of two subjective methods commonly used in clinics to measure horizontal heterophoria with an objective method implemented in a prototype of a new fully autonomous and automated vision analyzer (Eye and Vision Analyzer, EVA, DAVALOR, Spain), that records eye movements while the patient watches a true­3D short video game.


Measurements were performed in a group of 54 young healthy subjects. Monocular visual acuity at far and near distances equal or better than 0.0 logMAR was required. Subjective methods consisted of Von Graefe with a line of letters (VGL) and the Modified Thorington (MT) test. VGL was performed at 40 cm with an increment speed of prismatic diopters (PD) of 2PD/sec and under controlled conditions of ilumination (L≈450 lux). MT was performed at 40 cm with a RAF ruler and spotlight under controlled conditions of ilumination (L≈50 lux). Moreover, accurate instructions about stimulus alignment were given to the patients. Three measurements were performed for each method with an interval of 5 seconds between them. Objective measurements were made using an Alternant Cover Test procedure (OACT) showing the video game only in one eye during 2 seconds and recording the ocular movements. This procedure was also repeated three times. Runtime, including time for instructions, was also measured.


The mean age of the sample was 21.5±1.5 years (range:19 to 24). The mean horizontal heterophoria values were ­6.7±6.0 PD for VGL, ­1.0±3.8 PD for MT and ­2.0±3.0 PD for OACT. The mean value of differences was ­5,6±5,3 PD for VGL vs MT, ­4,6±4,6 PD for VGL vs OACT and 0,9±2,8 PD for MT vs OACT. The 95% confidence interval (Bland & Altman plot) was 10,48 for VGL vs MT; 9.83 for VGL vs OACT and 2.52 for TM vs OACT. The Intraclass Coefficient Correlation (ICC) was 61,2% for MT vs OACT; 61.9% for VGL vs OACT and 80.4% for TM vs OACT. The runtime was 137±20 sec for VGL;, 83±13 sec. for MT and 26±5 sec. for OACT


The EVA prototype is a useful device to objectively measure horizontal heterophoria using an Alternating Cover Test procedure. Results show a good ICC (>80%) when OACT is compared with MT. Differences between both methods (1PD) are not clinically significant and are within a good confidence interval. VGL shows higher differences and lower ICC when it is compared with OACT and MT. In addition, OACT is more than 3 times faster than MT and more than 5 times faster than VGL.

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Jaume Pujol
Director del DRC y Director del consejo clínico de Davalor

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