Purchase this article with an account.
Jennifer Kang Derwent, Robert A. Linsenmeier; Effects of Hypoxemia on the a- and b-Waves of the Electroretinogram in the Cat Retina. Invest. Ophthalmol. Vis. Sci. 2000;41(11):3634-3642.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
purpose. Slow components of the electroretinogram (ERG) are sensitive to even
mild hypoxemia (60 <
Pa o 2 < 100 mm Hg) in
the cat eye. However, the electrical responses of the inner retina
remain unchanged until Pa o 2 is
below 40 mm Hg. In this study, the effects of hypoxemia on
photoreceptors, on which both slow ERG components and inner retinal
activity depend, were examined by recording the a-wave of the ERG.
methods. The ERG of dark-adapted, anesthetized cats was recorded between an
Ag-AgCl electrode in the vitreous humor and a reference electrode near
the eye. Responses to bright flashes of diffuse white light were
recorded at 3-minute intervals during hypoxemic episodes lasting 15
minutes to 2 hours.
results. The cat a-wave was well described by the Lamb and Pugh a-wave model
during normoxia and hypoxemia. During mild hypoxemia (Pa o 2 of 50–60 mm Hg), small
changes in a-wave amplitude were detected but did not become greater
during severe hypoxemia. The mean decrease in the a-wave amplitude
during severe hypoxemia (Pa o 2 of
20–30 mm Hg) was 8.9% from the mean amplitude during air breathing.
The effects of hypoxemia were more severe on the b-wave amplitude. The
mean decrease in the b-wave was 35% at
Pa o 2 of 20–30 mm Hg.
conclusions. The a-wave is more resistant to severe hypoxemia than the b-wave. This
implies that photoreceptor transduction works almost normally during
hypoxemia and that failure of inner retinal Po 2 regulation causes the decrease in the b-wave. Previously observed
changes in the amplitudes of slow ERG components during hypoxemia may
result from changes in the ionic environment, rather than a failure of
photoreceptor energy metabolism.
This PDF is available to Subscribers Only