Increased Optic Nerve Head Capillary Blood Flow in Early Primary Open-Angle Glaucoma.
Gardiner Stuart K, Cull Grant, Fortune Brad, Wang Lin
AI Summary
This study found optic nerve head capillary blood flow was paradoxically increased in early glaucoma suspects, then decreased with functional loss but remained above healthy controls, suggesting complex vascular changes in human glaucoma.
Abstract
Purpose
Blood flow in the optic nerve head (ONH) is known to be reduced in eyes with advanced glaucoma. However, experimental results from non-human primates suggest an initial increase in ONH blood flow at the earliest stages of damage. This study assesses flow and pulsatile hemodynamics across a range of severities to test the hypothesis that this also occurs in human glaucoma.
Methods
Laser speckle flowgraphy was used to measure average mean blur rate (MBRave) within ONH tissue (a correlate of capillary blood flow) and the pulsatile waveform in 93 eyes with functional loss and 74 glaucoma suspect/fellow eyes without functional loss. These were compared against results from 92 healthy control eyes. Parameters produced by the instrument's software were age-corrected, then compared between groups using generalized estimating equation models.
Results
The mean MBRave in the control eyes was 12.5 units. In glaucoma suspect/fellow eyes, the mean was 16.4 units, higher with P < 0.0001. In eyes with functional loss, the mean was 13.8 units, lower than eyes without functional loss with P < 0.0001, although still higher than control eyes with P = 0.0096. Analysis of the pulsatile waveform suggested that the deceleration in flow as it approaches its maximum across the cardiac cycle was delayed in glaucoma.
Conclusions
Blood flow within ONH capillaries was higher in glaucoma suspect eyes than in healthy controls. It was less elevated in eyes that had developed functional loss. The mechanisms causing these changes and their relation to concurrent changes in pulsatile hemodynamics remain under investigation.
MeSH Terms
Shields Classification
Key Concepts4
The mean average mean blur rate (MBRave), a correlate of capillary blood flow within ONH tissue, in glaucoma suspect/fellow eyes (n=74) was 16.4 units, which was higher than in healthy control eyes (n=92) with P < 0.0001.
The mean average mean blur rate (MBRave) in eyes with functional loss (n=93) was 13.8 units, which was lower than in glaucoma suspect/fellow eyes (n=74) with P < 0.0001, but still higher than in healthy control eyes (n=92) with P = 0.0096.
Analysis of the pulsatile waveform in 93 eyes with functional loss, 74 glaucoma suspect/fellow eyes, and 92 healthy control eyes suggested that the deceleration in flow as it approaches its maximum across the cardiac cycle was delayed in glaucoma.
Laser speckle flowgraphy was used to measure average mean blur rate (MBRave) within ONH tissue and the pulsatile waveform in 93 eyes with functional loss, 74 glaucoma suspect/fellow eyes, and 92 healthy control eyes.
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