Purchase this article with an account.
S. Parks, T. Sandinha, A. Purdie, D. Keating; Do Rods have a significant influence on the photopic multifocal ERG response ? – An interesting case. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):4235.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose:To examine the effect of rod dysfunction on the multifocal ERG response. Methods:A 68 year old female patient presented with Vitamin A deficiency and associated nyctalopia. A standard wide field multifocal ERG and an ISCVE standard multifocal ERG was performed on presentation. A 61 area, 15 bit m–sequence was used to deliver the multifocal stimulus using an LCD Projection system. Signals were recovered from DTL electrodes using a filter bandwidth of 3 – 300 Hz and an amplifier gain of 100K. Following a course of treatment which comprised Vitamin A palmitate 100,000 units every 3 months intramuscularly injections, the electrophysiology was repeated. Results:At presentation, the Ganzfeld ERG showed no significant rod function and normal cone function. The multifocal ERG showed normal amplitude responses but a significant and diffuse delay in the p1 component (6 – 7 msec). After treatment, the Ganzfeld ERG Rod response showed a significant recovery in rod function with the response now clearly within normal limits (101 uV). Multifocal ERGs implicit times returned to normal and response amplitudes showed a significant reduction compared to pre–treatment but still within normal limits. Conclusions:The multifocal results show significant and diffuse implicit times delays in the absence of Rod function. When rod function returns then the implicit times return to normal and amplitudes of the multifocal response decrease. The multifocal ERG response is a composite response which reflects linear and non–linear processing in the retina. As stimulation rates are fast, it is generally believed that there is little or no contribution from the rods. This study shows that the rod system may have an inhibitory influence on the multifocal ERG response.
This PDF is available to Subscribers Only