Abstract
Purpose :
Dark adaptation of the retina is an energy requiring process generally assumed to be reflected by an increased retinal oxygen consumption. Consequently a reduced venous oxygen saturation could be expected.cf. Adlers Physiology of The Eye. In their pioneering work Einar Stefanson et.al. could not find evidence for this expectation; in contrast they found increased venous oxygen saturation during dark adaptation. However, the measurements were performed on central vessels with venous blood from both cone- and rod areas.
Hypothesis:The retinal venous oxygen saturation will decrease during dark adaptation, in veins draining predominantly rod containing areas of the retina, i.e the nasal part.
Methods :
17 normal volunteers without known eye diseases were participating (age 25-60 years) .First, Oxymap oximetry(Oxymap Retinal Oxymeter P3;Oxymap ehf,Reykjavik,Iceland) was performed in normal room illumination (180 lux).Total darkness was established while the investigated person was sitting in the oximeter chin rest and the camera position was fixated. After 10-12 min of dark adaptation oxymetry was performed in dark using the two adjustment beams for optimal focus. Oxymap analysis was performed tracing the peripheral parts of nasal veins(see figure). Repeated measurements were included in 11 participants within 2 weeks. Data were analyzed in a two sided model,taking into account the repeated examinations.
Results :
Mean venous oxygen saturation (%) in peripheral nasal retina is statistically significantly lower after adaptation (p<0.04). Mean difference between repeats were 7.6% for light and 6.9% for dark conditions.
Oxygen saturation (%) for all examinations: in light: 57.80 SD 8.63 min-max 39.00- 70.50, in dark: 56.00 SD 9.45 min-max 36.00- 68.70
Similar analysis was performed on the central vessels. There was a significant difference between light and dark adaptation with venous saturation HIGHEST in dark, but no difference between nasal and temporal veins, confirming the results of Stefansson et. al.
Conclusions :
The data support that dark adaptation of the human retina leads to a measurable DECREASE in the oxygen saturation of veins draining retinal areas with predominantly rods (nasal part of the retina).
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.