Optical blur effects on pattern & focal ERG in healthy eyes (V1.0).
Research type
Research Study
Full title
The value of comparing standard pattern and focal electroretinography under different conditions of optical blur in healthy adult participants.
IRAS ID
342012
Contact name
Anthony G. Robson
Contact email
Sponsor organisation
Research and Development Office, Moorfields Eye Hospital NHS Foundation Trust
Duration of Study in the UK
0 years, 5 months, 13 days
Research summary
Pattern electroretinogram (PERG) is a valuable test used to assess macular and retinal ganglion cell (optic nerve) function, to aid diagnostic assessment of retinal and neurological disease. The PERG is generated by a high contrast checkerboard stimulus (black and white checks display on a monitor; during recording, the checks reverse - black turns into white, and white turns into black), this checkerboard pattern can be attenuated by defocus, which affects the stimulus contrast. Optical defocus can therefore confound interpretation of a reduced PERG response, and the ability to reliably assess retinal function. The current International Society for Clinical Electrophysiology of Vision (ISCEV) Standard for PERG emphasises the need for optimal correction to accurately assess retinal responses.
Although used locally at Moorfields Eye Hospital, the focal electroretinogram (FERG; of 4 squares) is not widely used in other laboratories, however the FERG is now recognised as a potentially useful adjunct to standard pattern ERG testing by the current ISCEV standards updated and published in 2024. The PERG responses are markedly altered (amplitude reduction and/or shift in peak time) in a significant number of patients who attend unrefracted or forget to bring their spectacles. Such alterations can confound reliable assessment of central macular dysfunction, potentially leading to diagnostic inaccuracies, or the need for repeat testing, causing delay in clinical management.
The relationship between the degree of optical blur and relative influence on PERG and FERG is not fully understood. It would be advantageous to quantify the relative effect of optical blur on both types of response (to PERG and FERG pattern) in order to minimise measurement uncertainty and to inform interpretation in a healthy adult population.Summary of Results
The International Society for Clinical Electrophysiology of Vision (ISCEV) Standard pattern ERG (PERG) is a response to an alternating checkerboard stimulus composed of small checks. The PERG is used routinely to assess the function of the macula and optic nerve cells within the retina but is reduced by optical blur and non-optimal refraction. This study quantifies the effects of different levels of induced optical blur on the Standard PERG from adults without retinal disease, and compares responses to those recorded to a coarser checkerboard stimulus, composed of large checks (the “focal PERG”). Increasing levels of optical blur resulted in attenuation and increasing peak times of the Standard PERG P50 component by a predictable amount, whereas responses to the coarse pattern (focal PERG) were largely unaffected. The findings demonstrate that the focal PERG is a useful addition to ISCEV Standard PERG testing, as a comparison between the two test results can help expose optical contributions to PERG P50 alterations. This comparative technique informs clinical interpretation by differentiating between optical causes of pattern ERG reduction and those due to macular or optic nerve disease.REC name
London - Riverside Research Ethics Committee
REC reference
24/PR/1333
Date of REC Opinion
13 Nov 2024
REC opinion
Further Information Favourable Opinion