Abstract
The focal cone electroretinogram is a sensitive marker for macular disease, but have we unlocked its full potential? Typically assessment of waveform parameters is subjective and focuses on a small number of locations (e.g. the a-wave). This study evaluated the discriminatory and diagnostic potential of 4 conventional and 15 novel, objectively determined, parameters in patients with early Age-related Macular Degeneration. Focal cone electroretinograms were recorded in 54 participants with early Age-related Macular Degeneration (72.9±8.2 years) and 54 healthy controls (69±7.7 years). Conventional a and b wave amplitudes and implicit times were measured and compared to novel parameters derived from both the 1st and 2nd derivatives and the frequency-domain power spectrum of the electroretinogram.Statistically significant differences between groups were shown for all conventional parameters, the majority of 1st and 2nd derivative parameters and the power spectrum at 25 and 30 Hz. Receiver operating characteristics showed that both conventional and 1st and 2nd derivative implicit times had provided the best diagnostic potential. A regression model showed a small improvement over any individual parameter investigated. The non-conventional parameters enhanced the objective evaluation of the focal electroretinogram, especially when the amplitude was low. Furthermore, the novel parameters described here allow the implicit time of the electroretinogram to be probed at points other than the peaks of the a and b waves. Consequently these novel analysis techniques could prove valuable in future electrophysiological investigation, detection and monitoring of Age-related Macular Degeneration.
Highlights
Age-related Macular Degeneration (AMD) is the leading cause of irreversible vision loss in the western world and accounts for over 50% of all sight impairment registrations in the United Kingdom [1]
The participants with early AMD had smaller amplitudes and delayed implicit times for both the a and b waves compared to participants in the control group
The reductions in mean a and b wave amplitudes in the AMD group of 0.34 and 0.74 mV were both statistically significant (p,0.05), Receiver Operating Characteristics (ROC) analysis suggested a reduced diagnostic potential compared with their equivalent implicit times, returning area under the curve (AUC) values of 0.62 and 0.64, respectively
Summary
Age-related Macular Degeneration (AMD) is the leading cause of irreversible vision loss in the western world and accounts for over 50% of all sight impairment registrations in the United Kingdom [1]. The prevalence of AMD is expected to increase globally over the 40 years due to a predicted 3-fold increase in the number of people over 60 years of age [2]. An increasing number of mechanisms have been identified as possible targets for treatment development, in the early stages of disease [4]. The need, for sensitive, effective and ideally objective measures of retinal function [7], to evaluate these potential interventions in patients with early AMD, may never have been greater
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