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Photopic neural tests less sensitive to altered ocular hemodynamics than scotopic tests
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The retinal and choroidal nerves that generate photopic flash electroretinogram and oscillatory potentials in humans are largely unaffected by induced systemic hyperoxia and hypercapnia and their effects on retinal and choroidal hemodynamics, according to a study. These results contrast with previous work showing that scotopic testing under similar conditions was altered by hyperoxia and hypercapnia, the study authors said.
Helene Kergoat, OD, PhD, and David Tinjust, Orthoptist, MSc, at the University of Montreal examined the effects on the retinal and choroidal nerves of breathing pure oxygen or carbogen in 18 adult humans using the two neuro-ophthalmologic tests.
Breathing pure oxygen increased oxygen saturation and decreased heart rate and end-tidal carbon dioxide, but it did not alter respiratory rate and ocular perfusion pressure. Inhaling carbogen increase oxygen saturation, end-tidal carbon dioxide and ocular perfusion pressure and decreased the respiratory rate, but did not alter the heart rate.
The researchers found that the photopic flash electroretinograms and oscillatory potentials were not detrimentally affected by either the pure oxygen or carbogen. This contrasted with previous research showing that scotopic testing results were affected under similar conditions, the authors said.
The study is published in the March issue of Optometry and Vision Science.