Table 4. Components of variability in vascular SO₂ measurements by retinal oximetry.

		Components of Variability in Absolute Numbers				Components of Variability in Terms of % of Total Variability
Group	Vessel Type	Between Subject SD (%SO2) *	Between Vessel SD (%SO2) †	Same Vessel SD (%SO2) ‡	Total SD (%SO2)§	Between Subject SD (%)*	Between Vessel SD (%)†	Same Vessel SD (%)‡	Total Variability (%)§
Unirradia ted group	Venules	2.23%	5.06%	2.39%	6.02%	14%	71%	16%	100%
	Arterioles	2.23	2.79	1.70	3.95	32	50	18	100
Irradiated group	Venules	3.63	8.19	2.50	9.30	15	78	7	100
	Arterioles	3.63	4.52	1.77	6.06	36	56	9	100

SD: standard deviation.

^*Variability in SO₂ measurements between subjects within subject group and vessel types subgroups.

^†Variability in SO₂ measurements between vessels in the same subject.

^‡Variability in repeated SO₂ measurements of the same vessel in the same subject.

^§Root-sum-square of the between-subject, between-vessel, and same-vessel SD components.