Related Experiment Video
Updated: May 1, 2026
07:45
Assessing Binocular Central Visual Field and Binocular Eye Movements in a Dichoptic Viewing Condition
Published on: July 21, 2020
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Visual field coordinates of pupillary circular axis and optical axis
David A Atchison1, Ankit Mathur, Marwan Suheimat
1*PhD, DSc, FAAO †PhD, FAAO ‡PhD §DSc Institute of Health & Biomedical Innovation and School of Optometry & Vision Science, Queensland University of Technology, Kelvin Grove, Queensland, Australia (DAA, AM, MS); and Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom (WNC).
Summary
The pupillary circular axis (PCAx), where the pupil appears most circular, is similar to the optical axis. However, the optical axis shows greater individual variation, suggesting the pupil can be modeled as circular along the line-of-sight.
Area of Science:
- Ophthalmology
- Optometry
- Vision Science
Background:
- The pupil's shape and orientation change with the visual field angle.
- Understanding these changes is crucial for accurate eye modeling and optical performance analysis.
Purpose of the Study:
- To determine and compare the pupillary circular axis (PCAx) and optical axis.
- To analyze their horizontal and vertical coordinates along the horizontal meridian of the visual field.
Main Methods:
- Pupil images were analyzed for ellipticity and orientation across visual field angles (±90 degrees).
- Refractive astigmatism was used to determine the optical axis across field angles (±35 degrees).
- Data were collected from 30 participants' right eyes.
Main Results:
- The mean PCAx coordinates were -5.3° (horizontal) and -3.2° (vertical).
- The mean optical axis coordinates were -4.8° (horizontal) and -1.5° (vertical).
- Vertical coordinates differed significantly (p=0.03), with no significant correlation between the axes.
Conclusions:
- The PCAx and optical axis are, on average, similarly displaced from the line-of-sight.
- The optical axis exhibits greater intersubject variability.
- Modeling eye optics can reasonably assume a circular pupil along the line-of-sight.
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