Changes in retinal blood flow and oxygen metabolism may accompany increasing diabetic retinopathy (DR) severity. A retrospective study published in Acta Ophthalmologica evaluated optic nerve head (ONH) blood flow, pulse waveform parameters, and retinal oxygen saturation across different stages of DR.

The analysis included 72 patients categorized by DR severity into mild-to-moderate non-proliferative diabetic retinopathy (NPDR), severe NPDR, and proliferative diabetic retinopathy (PDR). Retinal oximetry and laser speckle flowgraphy measurements were performed to assess retinal oxygen saturation and blood flow parameters.

Findings

• Retinal arteriolar oxygen saturation was significantly higher in the PDR group compared with both mild-to-moderate NPDR and severe NPDR (p = 0.006 for both comparisons).
• Retinal venular oxygen saturation was significantly higher in the PDR group compared with mild-to-moderate NPDR (p = 0.016) and severe NPDR (p = 0.021).
• Mean blur rate (MBR)-vessel, representing retinal blood flow velocity, was significantly lower in the PDR and severe NPDR groups compared with mild-to-moderate NPDR (p = 0.001 and p = 0.041, respectively).
• MBR-tissue, representing ONH blood flow velocity, was also significantly lower in the PDR and severe NPDR groups (p = 0.024 and p = 0.028, respectively).
• Flow acceleration index was significantly lower in the PDR group compared with mild-to-moderate NPDR (p = 0.006).

Greater DR severity was associated with lower retinal and ONH blood flow velocities together with higher retinal oxygen saturation, particularly in severe NPDR and PDR.