Oxygen Saturation
Saturation in
in Human
Human Retinal
Retinal Arterioles
Arterioles and
and Venules
Venules is
is Lower
Lower in
in Light
Light than
than in
in Dark
Dark
4172 Oxygen
Results
Results
The figures below summarize the results for arterioles (fig.
4), venules (fig. 5) and arteriovenous difference (fig. 6).
110
Methods
Methods
Our automatic oximeter non-invasively yields fundus
images with 4 wavelengths of light simultaneously.
Figure 2. Automatic selection of measurement points.
p=
0.054
0.042
0.004
0.032
0.149
100
90
80
70
Minutes
Figure 3. An example of a color-coded map of
hemoglobin oxygen saturation. The map is generated
automatically by the oximeter. This patient had diabetes
but no retinopathy.
We performed oximetry in 17 healthy volunteers. First
degree arterioles and venules were measured in one eye
of each subject. The subjects were first placed in the dark
for 30 minutes, then alternatingly in light and dark; each
light or dark period lasting for 5 minutes. Oximetry was
performed at the end of each period. Altogether, 6
measurements were made on each individual. The room
light was approximately 80cd/m2. Statistical analysis was
done by paired t-tests.
Figure 1. The retinal oximeter.
Above: Components. Below: A typical output.
Venous SatO2 (%)
70
p=
0.034
0.028
0.006
0.006
0.138
60
0.094
Minutes
30
35
40
45
50
55
Dark Light Dark Light Dark Light
Figure 5. Retinal venous saturation after 30 min. of dark
adaptation and after 5 subsequent periods of either room
light or dark. The graph shows means and SD.
0.138
0.190
0.540
40
30
20
Minutes
30
35
40
45
50
55
Dark Light Dark Light Dark Light
100
95
90
85
80
75
Minutes
30
Dark
40
0.200
50
70
50
30
p=
105
30
35
40
45
50
55
Dark Light Dark Light Dark Light
Figure 4. Retinal arterial saturation after 30 min. of dark
adaptation and after 5 subsequent periods of either room
light or dark. The graph shows means and SD.
60
Figure 6. Retinal arteriovenous difference in saturation
after 30 min. of dark adaptation and after 5 subsequent
periods of either room light or dark. The graph shows
means and SD.
Arterial SatO 2 (% )
Earlier studies on animals have indicated that oxygen
tension in the inner retina is lower in light than in dark
(Linsemeier, Braun 1992), whereas the oxygen
consumption in the retina as a whole is lower in light
(Stefánsson et al 1983, 1988). The purpose of the study
was to measure the hemoglobin oxygen saturation (SatO2)
in retinal vessels after periods of dark and light in human
subjects.
Specialized software automatically selects points on
vessels and adjacent fundus for calculation of optical
density ratios (ODRs). ODRs have an approximately
linear inverse relationship with hemoglobin oxygen
saturation (SatO2) (Beach JM et al. 1999).
Arterial SatO2 (%)
Purpose
Purpose
AV difference SatO2 (%)
1A, S.H. Hardarson1A
1A G.H. Halldorsson1B
1B R.A. Karlsson1B
1B J.M. Beach1B
1B T. Eysteinsson1A
1A J.A. Benediktsson1B
1B A. Harris22, E. Stefansson1A
1A
S.Basit
Basit1A
S.
, S.H. Hardarson ,,G.H.
Halldorsson ,,R.A.
Karlsson ,,J.M.
Beach ,,T.
Eysteinsson ,,J.A.
Benediktsson ,,A.
Harris , E. Stefansson
Ophthalmology, BBElectrical
Electricaland
andComputer
ComputerEngineering,
Engineering,11University
Universityof
ofIceland,
Iceland,22Ophthalmology,
Ophthalmology,Indiana
IndianaUniversity
University
AAOphthalmology,
35
Light
40
Dark
Figure 7. Raw data from first three measurements on
arterioles. Each line connects measurements from one
individual.
Conclusions
Conclusions
These results suggest that the hemoglobin oxygen
saturation is lower in both retinal arterioles and venules
when the retina is in light compared to when it is in dark.
Commercial relationship: S. Basit, None; S.H. Hardarson, Oxymap ehf., I; Oxymap ehf., P; G.H.
Halldorsson, Oxymap ehf., I; Oxymap ehf., E; Oxymap ehf., P; R.A. Karlsson, Oxymap ehf., I; Oxymap
ehf., E; Oxymap ehf., P; J.M. Beach, Oxymap ehf., I; Oxymap ehf., P; T. Eysteinsson, Oxymap ehf., I;
Oxymap ehf., P; J.A. Benediktsson, Oxymap ehf., I; Oxymap ehf., P; A. Harris, Oxymap ehf., I; E.
Stefansson, Oxymap ehf., I; Oxymap ehf., P.
Support: Icelandic Research Council, Icelandic Fund for Prevention of Blindness, University of Iceland
Research Fund, Landspitali - University Hospital Research Fund.