Abstract
Purpose:
To detect subtle changes in retinal oxygenation along different segments of retinal vessels.
Methods:
A retrospective case cohort study was performed. Fifty cases were selected. Retinal oximetry was performed as part of the evaluation of these patients (Oxymap, Reykjavik, Iceland). One optic disc-centered image was obtained per eye. Each image was processed with the Oxymap analyzer software version 2.3.1, and evaluated as follows: A circle was centered over the optic disc to cover its margin. The image is divided into 4 quadrants (superotemporal, superonasal, inferotemporal and inferonasal). A concentric inner circle was drawn around the central circle. Two other outer circles were drawn. The regions between the innermost and the outermost concentric circles defined the measurement area to be analyzed. Measurements were generated separately for all arterioles and venules within the measurement area. Primary objective measures were changes in SaO2 and SvO2 along the different segments of retinal vessels. These changes were then evaluated based on the retinal pathology. Statistical analysis was performed using a paired t-test with p 0.05.
Results:
One hundred eyes/images were evaluated. Thirty cases of ischemic conditions (i.e. diabetes, retinal vein occlusions, sickle cell disease), 8 cases of hereditary diseases (Retinitis pigmentosa, Stargardt’s disease), 7 cases of degenerative disorders (age related macular degeneration) and 5 patients with no identifiable ocular pathology. SaO2 values were similar in all quadrants, in all segments of the vessel and in all cases (non-statistically significant value). SvO2 values in superotemporal quadrant were slightly greater compared to other quadrants but with non-statistically significant difference p 0.09. SvO2 values also showed a non-statistically significant difference between different segments of the same vessel. SvO2 values were statistically significant different among different retinal conditions, with the lowest values shown in ischemic disorders.
Conclusions:
Retinal arterioles oxygen saturation is similar in all quadrants of the retina independently of the diagnosis. Retinal venules oxygen saturation varies among several retinal disorders with a greater impact in ischemic conditions. These variations are more evident in the superotemporal quadrant of the retina but with minimal changes along different segments of the vessels.