Abstract
Purpose :
A huge quantity of research has explored retinal vessel oxygen saturation (SO2) in health and pathology to determine normative data but also changes in pathologies known for the involvement of tissue hypoxia. However, commercial devices have not made their way into clinical practice yet. This meta-analysis (MA) aims to explore normative data for SO2 measurements applying dual wavelength oximetry and confounding factors to explain variation in SO2 in healthy participants.
Methods :
After registering with PROSPERO (CRD42023365032) and following the PRISMA guidance, a keyword search of 4 databases (Web of Science, Scopus, PubMed, CINAHL) by 2 independent researchers, citation search and critical appraisal using the JBI tool was carried out. Search phrase was ((retina) OR (retinal vessel)) AND ((oximetry) OR (oxygen saturation) OR (saturation)) AND ((healthy) OR (normative) OR (normal) OR (data base) OR (standard)) AND ((dual wavelength) OR (photography)). The search included studies published until March 2023. Pooled normative data of artery and vein SO2 were analysed using a random effects model (Meta-Essentials V1.5). Publication bias analysis was assessed by Egger Regression. To investigate heterogeneity (I2), subgroup analysis (ethnicity, device) and regression analysis (age, mean arterial pressure (MAP)) were performed.
Results :
Out of 311 studies, 38 (n=1873) were used to analyse normative data. Pooled artery SO2 and vein SO2 were 94% and 58%, with precision intervals of PI (89%; 98%) for artery SO2 and PI (50%; 66%) for vein SO2. Heterogeneity was high for artery and vein SO2 (90%, p<0.01 and 94%, p<0.01). Accounting for ethnicity, device did not reduce heterogeneity. Age and MAP showed no significant effect on SO2 for arteries and veins.
Conclusions :
High heterogeneity indicates the influence of confounding factors. Confounding factors such as device, ethnicity, age and MAP investigated in this study did not improve heterogeneity. This suggests that dual wavelength oximeters are comparable. Moreover, the precision intervals found in this study might reflect a normal physiological variation in otherwise healthy individuals. This highlights the importance of other physiological measures when reporting SO2 results.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.