Investigating human retinal function in vivo using the electroretinogram: rod and cone-driven responses in the dark, associations with a myopia risk variant, and retinal dark adaptation in health and disease
Year: 2024
Type: dissertation
Study design: Observational Study
Abstract: The electroretinogram (ERG) is the electrical response of the retina to light stimuli, and can be recorded non-invasively. This thesis investigates aspects of human retinal function using the ERG "Electronegative" ERGs, their physiological basis, and clinical associations are reviewed. Subsequent chapters analyse ERG responses recorded from over 200 healthy adult twins. The distribution of b:a ratios in waveforms elicited by standard flashes delivered in the dark is examined: no participants showed negative waveforms, supporting the notion that such waveforms are of clinical significance. Next, the thesis examines responses elicited by standard strong flashes delivered in the presence of a rod-saturating blue background to explore dark-adapted cone system responses. Around 20% of these responses exhibit a negative waveform, suggesting that it is a characteristic of the dark-adapted cone system response in some individuals. The thesis also analyses isolated rod-system responses and quantifies correlations between dark-adapted rod and cone-driven ERG parameters with age, and their heritability. Most amplitudes decline with age whilst peak times become more delayed. The significant heritability of these parameters emphasizes the role of genetic factors in determining response variability. Additionally, the thesis investigates associations between ERG parameters and genotype at a myopiaassociated risk locus near the GJD2 gene. Significant associations are found with cone-driven signals, consistent with the importance of cone-driven signalling in myopia development. Finally, the thesis explores use of ERG to track the recovery of retinal sensitivity in the dark following light-adapting exposure. This includes a comprehensive review of previous studies and a description of a pragmatic ERG protocol for tracking panretinal rod system recovery following in the dark. The research reveals evidence of slowing recovery with increasing age and identifies delays in patients with Vitamin A deficiency and Sorsby fundus dystrophy, consistent with an "ocular vitamin A deficiency" in the latter condition.
Author: Jiang, Xiaofan
Language: English
Subfield: Ophthalmology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W7038547699