Clinical Ophthalmology (Nov 2022)
Effect of Pupil Size on Fixed-Luminance Flicker Full-Field Electroretinogram Magnitude
Abstract
Azadeh Mobasserian,1,* Moosa Zaidi,1,* Sohail Halim,1,2 Jaclyn Joyce Hwang,1 Jonathan Regenold,1 Amir Akhavanrezayat,1 Irmak Karaca,1,3 Hassan Khojasteh Jafari,1 Negin Yavari,1 Wataru Matsumiya,1,4 Cigdem Yasar,1,5 Ngoc Tuong Trong Than,1 Gunay Uludag,1 Diana Do,1 Hashem Ghoraba,1 Quan Dong Nguyen1 1Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, Palo Alto, CA, USA; 2Ocular Imaging Research and Reading Center, Sunnyvale, CA, USA; 3Department of Ophthalmology, Ege University Faculty of Medicine, Izmir, Turkey; 4Division of Ophthalmology, Department of Surgery, Kobe University Graduate School of Medicine, Kobe, Japan; 5Department of Ophthalmology, Suleyman Demirel University, Faculty of Medicine, Isparta, Turkey*These authors contributed equally to this workCorrespondence: Quan Dong Nguyen, Spencer Center for Vision Research, Byers Eye Institute, Stanford University School of Medicine, 2370 Watson Court, Suite 200, Palo Alto, CA, 94303, USA, Tel +1 650 725-7245, Fax +1 650 736-8232, Email [email protected]: Diopsys® NOVA fixed-luminance flicker full-field electroretinogram (ffERG) device is a potential adjunct to conventional flicker ffERG testing for assessing cone cell function. Magnitude of measured electrical response is known to vary with pupil size in conventional ffERG testing. The index study characterizes the relationship between magnitude of measured electrical activity and pupil size, both pupil diameter and pupil area, for this device.Methods: Seventeen patients (34 eyes) with no known ocular diseases were enrolled in the study. Electrophysiologic function of cone cells was evaluated using fixed-luminance flicker ffERG before and after dilation. Linear regression models, with inter-eye correlations controlled as fixed-effects, were used to characterize the effect of pupil dilation on the magnitude of the measured responses.Results: Mean age of study patients was 33.5 (standard deviation 7.4 years), and 35.3% of the subjects were female. Mean value of electrical response magnitude was 10.07± 2.79μV before dilation and 15.30± 4.08μV after dilation. The correlations of ERG magnitude with pupil diameter and with pupil area were not significant for either dilated or undilated eyes considered separately but were highly significant (p< 0.001) for dilated and undilated eyes considered in aggregate. ERG magnitude tended to increase by 1.08 μV for every 1 mm increase in pupillary diameter.Conclusion: An increase in pupil size, both pupil diameter and pupil area, is significantly associated with an increase in flicker ffERG magnitude recorded by the Diopsys device, suggesting that pupil size should be measured and considered when making clinical judgments based on the flicker ffERGs recorded by the device, and that pupil size-specific reference ranges could improve the clinical utility of the device.Keywords: electroretinogram, ERG, flicker ERG, pupil, magnitude, Diopsys
