Purchase this article with an account.
F. Moret, A. Doelemeyer, L. Schmetterer, G.N. Lambrou; A novel ophthalmic camera–based fundus–controlled multifocal ERG instrument for monitoring retinal function . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4248.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: To develop a fundus–controlled mfERG system for application in non–human primates and humans, allowing accurate (re–) positioning of the stimuli onto the retina for assessment of retinal function and accurate spatial monitoring of changes over time. Methods: A fundus camera (TRC–F, Topcon America Corp, NJ) and a miniature CRT based mfERG stimulator (Veris Fundus, Electro–Diagnostic Imaging Inc, CA) were modified into a single instrument. The optical design has been adapted to meet the requirements of monkey eyes, namely a pupil size smaller than 5.5 mm. The fundus camera has been modified for infrared operation, not to interfere with the visible stimulus. The instrument was characterized for compliance with the International Society of Clinical Electrophysiology in Vision (ISCEV) guidelines. Maximum and minimum luminance of the stimuli were measured at the retinal plane of an artificial eye using a CCD sensor calibrated by an illuminance meter. The system has been evaluated in 6 healthy eyes of 6 cynomolgus monkeys. First order responses to an unscaled 103 hexagons stimulus pattern were recorded 6 times successively with new positioning for each recording. Individual positions were documented with fundus pictures for evaluation of the positioning accuracy. For each eye one recording was performed with the same Veris system but using the conventional CRT screen. Results: Simultaneous stimulation/recording (40° visual angle, 75 Hz frame rate) and infrared fundus observation (20° visual angle, 10 Hz frame rate) are archived. The luminance of the hexagons in dark and bright state have been adjusted to 0.5 and 100 cd/m2, respectively. The first order response exhibit the typical characteristics of mfERG signals, such as standard waveform, peak at the fovea and reduced signal at the optic nerve head. It compares well to the response recorded using the conventional CRT screen. The accuracy of repositioning the stimulus pattern on the retina was evaluated to be smaller than 0.5° visual angle. Conclusions: The new fundus–controlled mfERG instrument has been made compliant with the ISCEV guidelines. The system allows recording of mfERG responses with simultaneous fundus observation, permitting accurate positioning of the stimulus pattern on the retina. Hence, it enables spatial monitoring of retinal function over time for follow–up of diseases related changes. The instrument can be applied to the human eye without modifications.
This PDF is available to Subscribers Only