Centre for Sensors, Instruments and Systems Development

Universitat Politècnica de Catalunya

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Effect of proximity clues in pupil measurements

Effect of proximity clues in pupil measurements
A study by researchers at CD6 and DAVALOR Research Centre (DRC) associates the proximal accommodation to pupil measurements, demonstrating that the intrument design is a source of variability that may introduce clinically unacceptable differences when comparing different pupil measurement devices.

The study, conducted by Carlos Otero, Mikel Aldaba Juan Carlos Ondategui and Jaume Pujol, was developed under the support of the Researchers Training Grants Program of the Government of Catalonia, the National Plan for R+D of the Spabish Ministry of Economy and Competitvity (DPI2011-30090-C02-01) that includes ERDF funds from the European Union and support the company Davalor Salud.

The results were presented at the 31st International Pupil Colloquium held at the University of Oxford in Pembroke College.


Pupil diameter of 18 patients were dynamically recorded (at 25 Hz) during 3 seconds in the following 4 conditions of vision: 1) monocular vision without any proximity clue placed between 1 m and the patient’s eye, 2) monocular vision with proximity clues, 3) monocular vision through a squared aperture of 30x30 mm placed 20 mm away from the eye, 4) binocular vision without proximity clues. All measurements were performed in mesopic (2 Lux) and photopic (1600 Lux) conditions. Randomization of each condition was done. The open-field autorefractor/pupilometer PowerRef II (PlusOptix, Germany) was used.

Repeated measures ANOVA among configurations 1 to 4 in mesopic conditions showed statistically significant differences: F(df=1.902,error=32.334)=10.544, p<0.001.
The Bonferroni post-hoc test showed that the mean pupil diameter difference [95% confidence limits] between the fourth condition minus the 1, 2 and 3 were respectively (in mm): -0.83 [-1.44, -0.21], -0.53 [-0.80, -0.25], -0.93 [-1.60, -0.26]. Analogously, the mean pupil difference [95% confidence limits] between the second condition minus the 1 were respectively (in Diopters): -0.30 [-0.84, 0.24].
In photopic conditions, the repeated measures ANOVA also turned out to be statistically significant: F(df=3,error=48)=38.675, p<0.001. The Bonferroni post-hoc test showed similar comparisons than the mesopic ones.

Binocular pupil measurements are significantly different (>0.5 mm) to monocular pupil measurements. It is also shown that pupil measurements with open-field designs can be significantly different to closed-field measurements in some patients.
Moreover, our findings showed a tendency towards a decrease in pupil diameter when proximity clues are present in both illumination conditions, which suggests that proximal accommodation seems to induce significant pupil miosis in some patients (in closed-loop conditions). Nonetheless, further studies that take into account accommodation control and report refraction data in synchronization with pupil data would be beneficial for more robust conclusions.
CD6 Centre for Sensors, Instruments and Systems Development
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