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Tamsin Callaghan, Alison Binns, Tom Margrain; Functional biomarkers of hypoxia in Age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2655.
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© ARVO (1962-2015); The Authors (2016-present)
Hypoxia has been implicated in the aetiology of Age-related Macular Degeneration (AMD). Scotopic thresholds are elevated in a similar way by AMD as they are by hypoxia in the absence of AMD. This supports the hypothesis that local retinal hypoxia is responsible for the deficits in scotopic function reported in AMD. The purpose of this study was to compare the effect of transient systemic hypoxia on scotopic visual function in participants with and without early AMD to test the hypothesis that people with AMD are more susceptible to visual dysfunction in hypoxic conditions than healthy controls.
Scotopic thresholds (QUEST paradigm, 40 trials), and dark adapted ERGs (full-field rod response, 0.5Hz, blue, 5ms, 0.125cd/m2; focal cone flicker response, 40 Hz, red, 80cd/m2) were measured in 16 participants with early AMD and 19 age-matched controls over two visits. Data were collected when participants were breathing 14% oxygen and medical air (21% oxygen). Peripheral oxygen saturation (SpO2) was monitored using a pulse oximeter. Gas order was randomised, and participants were masked to the gas being supplied. Thresholds and ERG parameters were compared between gas conditions and between groups.
SpO2 levels dropped significantly when breathing 14% oxygen compared to medical air for both groups for both visits (p< 0.001) and the SpO2 was also significantly lower in the AMD group for the scotopic threshold visit (<0.001). Thresholds were significantly higher in the AMD than the control group when breathing 21% oxygen (p= 0.049) but not 14% oxygen (p=0.130). There were no significant differences in the scotopic thresholds within each group when breathing 14% oxygen compared to medical air (P>0.05).There were no significant differences in full-field ERG parameters between the 2 gases, or between groups, apart from the amplitude of the b-wave which was significantly reduced under the hypoxic condition in the control group (p=0.028). There were no significant differences in any parameters of the focal ERG either within or between the groups.
There was no evidence in this study that induced systemic hypoxia has a greater effect on scotopic visual function in people with AMD. Indeed, although the scotopic ERG b-wave was reduced in amplitude in both groups when breathing 14% oxygen, this difference was only significant in the control group.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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