Influence of pupil size and other test variables on visual function assessment using visual evoked potentials in normal subjects.

The purpose of this study was to assess the influence of pupil size and optical blur on measurements obtained with isolated-check visual evoked potential (icVEP). Two stimulus conditions of icVEP, +15 and -15% contrasts, were studied in normal subjects with normal (N), miotic (M), and dilated (D) pupils. The effects of optical blur were studied in subjects with normal pupil. Response to visual stimuli was quantified by a signal-to-noise (SNR) ratio. In 30 normal subjects, the mean age was 26.0 +/- 3.4 years. Mean pupil diameters were N = 4.2 +/- 0.6 mm, M = 2.7 +/- 0.6 mm, and D = 7.3 +/- 0.9 mm. For both +15 and -15% contrast levels, mean SNR values were reduced for dilated and constricted pupils when compared with normal pupils. Mean SNR values for optical blur with a +2 or +3 diopter lens placed over the distance correction were reduced when compared with SNR measurements obtained with best-corrected visual acuity under both +15 and -15% contrast levels. Statistical significance was found in comparisons of N versus M (P < 0.001) and N versus D (P = 0.002) for +15 and -15% contrast conditions, respectively. No statistical difference was seen for M versus D (P = -0.435). The effect of optical blur was statistically significant when compared to the normal pupils with best-corrected vision (P < 0.001). No statistically significant difference was found comparing +2 and +3 diopters lenses for optical blur testing. Visual evoked potential values are influenced by pupillary constriction and dilation, as well as optical blur. When obtaining icVEP measurements, the influence of pupil size and optical blur should be kept in mind for accurate interpretations.

Guest editors

Enid Chelva

Dr. Steve Colley

Dr. Jane Khan

A/Prof. Timothy Lai

Prof. Ted Maddess

Prof. Atsushi Mizota

Editorial

This special issue of Documenta Ophthalmologica documents the proceedings of the XLVIIIth ISCEV Annual Symposium, held in Fremantle, Western Australia, from 6th to 10th November, 2010.

The two main symposium themes were “Electrophysiology, Genetics and Imaging in Retinal Disease” and “Stimulus Paradigms in Multifocal Electrophysiology”, which were supported by Invited Lectures Prof. David Mackey, Prof. John Hecklenlively and Prof. Erich Sutter.

The ISCEV Keynote Lecture, “The cellular origin of different components of the electroretinogram”, was presented by Prof. Trevor Lamb and the prestigious Emiko-Adachi Lecture, entitled “Establishment of the concept of new clinical entities—complete and incomplete CSNB and occult macular dystrophy”, was delivered by past ISCEV President, Prof. Yozo Miyake.

The Symposium hosted a Special Session on “Extended Protocols”, organised by Prof. Mitch Brigell, Prof. Mike Marmor and Prof. Eberhart Zrenner, and two pre-conference courses, “Clinical Electrophysiology of Vision (Human)”, coordinated by Prof. Graham Holder, and “Animal Electrophysiology and Imaging”, directed by Prof. Mathias Seeliger.

Editorial notes

The abstracts in this issue have been edited and re-set to a standard format. The Scientific Program Committee has made every effort to respect the intended meaning in the original submissions and apologises for any inadvertent misinterpretation.

Abbreviations are defined within each abstract except for the following which are used without definition throughout: cpd—cycles per degree, EOG—electro-oculogram, ERG—electroretinogram, ISCEV—International Society for Clinical Electrophysiology of Vision, l-cone—long-wavelength cone, m-cone—medium-wavelength cone, mf—multifocal, when used in conjunction with ERG, PERG, PhNR, OP or VEP, OP—oscillatory potential, PERG—pattern electroretinogram, PhNR—photopic negative response ERG, s-cone—short-wavelength cone, VEP—visual evoked potential.

Enid Chelva

Chair, Scientific Program Committee.