Pupil Diameters Larger in Early Glaucoma, Testing Finds

Ophthalmologist measuring intraocular pressure of woman in clinic
Researchers use visual evoked potential testing to uncover significant differences between pupil diameters in healthy and glaucomatous eyes.

Pupil diameters tested with visual evoked potential (VEP) were significantly larger in newly diagnosed open-angle glaucoma patients than in healthy controls, according to a study published in the October 2020 issue of Optometry and Vision Science.

Researchers conducted the retrospective study to determine if pupillometry could be a new objective method for glaucoma detection and monitoring. Researchers tested 24 eyes of 14 female and 10 male patients who had been recently diagnosed with open-angle glaucoma, and 30 eyes of 30 healthy participants as a control group using visual evoked potential (VEP), standard automated perimetry, and pupillometry. 

Investigators found no significant difference between males and females for photopic pupil diameters in either group. However, when comparing pupil diameters at 3 different luminance levels — 60 cd/m2, 100 cd/m2, and 130 cd/m2 — they found that pupil diameters were significantly larger in the glaucoma patient group. 

Using photopic measurements performed at 60 cd/m2 luminance, pupil diameters were approximately 3.21 mm for the study group and 2.76 mm for the controls. It was 2.94 mm in the study group using 100 cd/m2 luminance and 2.54 mm in the control group. Using 130 cd/m2 luminance, the study group was approximately 3.01 mm while the control group was 2.56 mm.  

Additionally, they found significant correlations between photopic pupil diameters and the timing of VEP waveforms.

“Our results suggest that measuring pupil diameter may provide an additional objective method to detect and monitor glaucoma. However, pupil diameter should be evaluated in larger populations of healthy individuals and in different categories of glaucoma patients,” the researchers explain. 

“In addition, factors that do not relate to optic nerve damage, such as mechanical properties of the iris, systemic conditions, or medications, may result in variable responses in pupillary light responses.” 

The authors noted the study’s limitations included its retrospective design, small size, select patient group, and lack of a standardized pupillometry method. 


Işik MU, Şahin OF. The Relationship between pupillometric values and visual evoked potential test results in patients with early glaucoma. Optom Vis Sci. 2020:97(10):898–902. doi: 10.1097/OPX.0000000000001589.