Differences in Blood Flow Between Superior and Inferior Retinal Hemispheres.

Area of Science:

• Ophthalmology
• Retinal Physiology
• Vascular Biology

Background:

• Retinal blood flow is crucial for maintaining visual function.
• Understanding regional differences in retinal perfusion is important for diagnosing and treating eye diseases.
• Previous studies have not fully elucidated the differences in blood flow between the superior and inferior retina or the impact of posture.

Purpose of the Study:

• To investigate significant differences in blood flow between the superior and inferior retina.
• To determine the effect of body posture on retinal blood flow in these regions.

Main Methods:

• Laser speckle flowgraphy was used to measure blood flow around the optic nerve head in 68 healthy subjects.
• Blood flow was assessed in both sitting and supine positions, with measurements taken at various time points after postural change.
• Key parameters measured included relative flow volume (RFV), mean diameter, and mean blur rate (MBR) in arterial and venous vessels.

Main Results:

• Significantly greater total relative flow volume (RFV)-all, RFV-artery, and RFV-vein were observed in the superior retina compared to the inferior retina (P < 0.001).
• Mean diameter-all and mean diameter-artery were also significantly larger in the superior retina (P < 0.05).
• Mean blur rate (MBR)-all, MBR-artery, and MBR-vein were elevated in the superior retina (P < 0.001, P < 0.01, P < 0.001, respectively).
• Despite changes in ocular perfusion pressure due to postural alteration, the superior retina consistently showed higher total RFV-all.

Conclusions:

• The superior peripapillary retina exhibits significantly higher blood flow and larger vessel diameters than the inferior peripapillary retina.
• These regional differences in retinal blood flow are maintained even when body posture is altered.
• Clinicians should consider these anatomical and physiological variations when evaluating retinochoroidal diseases.