Abstract
Introduction Oxygen saturation in retinal vessels can be non-invasively measured by a new method.
It is known that oxygen extraction is lowered in diabetic retinopathy. In the
cross-sectional study presented here, it has been investigated whether diabetes-specific
changes and typical accompanying diseases could influence the measurements in oximetry.
Methods During a time span of seven months, 237 diabetics were included who came to our clinic
for an intravitreal injection, who met the inclusion criteria, who showed no exclusion
criteria and gave written consent. 203 eyes of 203 patients were evaluated. The
oxygen saturation (SO2) was measured in digitally stored fundus images taken with a fundus camera
(Zeiss 450 FF). In its illumination beam, a filter was inserted with two transmission
maxima at 584 nm and 610 nm (bandwidth 10 nm). With the program “Oximetry” (Imedos
Systems, Jena,
Germany), the venous and the arterial SO2 were measured. The values were stored in a spreadsheet. Diabetes related data, clinical
parameters and accompanying diseases were
documented in the predefined scheme.
Results In the whole patient sample, the venous oxygen saturation (vSO2) was 69 ± 12%, the arterial saturation (aSO2) 99 ± 5% and the arteriovenous difference
31 ± 9%. A statistically significant association could not be found between the
measurement values of oximetry and age, duration of diabetes and HbA1c (Kruskal-Wallis ANOVA:
p > 0.05). The differences in oximetry values between units of analysis (UOA)
e.g. hypertension and non units of analysis (NOA) were analysed. Descriptive testing
showed significant
differences in vSO2% in the following units of analysis: allergies n = 47: UOA vs. NUOA: 64 vs. 69 (t
test: p < 0.02); sartan therapy n = 46: UOA vs. NUOA: 64 vs. 70
(p = 0.003); state after intravitreal injections n = 144: 68 vs. 71 (p = 0.02).
Oxygen extraction from the retinal capillaries was improved in patients who had injections
with VEGF
inhibitors. An improvement in oxygen extraction is also seen in patients with
allergies and hypertension in comparison to those without these units of analysis.
Conclusion The clinically observed improvement in the retinal state situation after intravitreal
injections with VEGF inhibitors may be seen in association with the improved oxygen
extraction. It seems reasonable to study whether a switch to sartans in the therapy
of hypertension may improve retinal function.
Key words
retina - diabetes mellitus - oximetry - sartans - VEGF inhibitors - allergy
