Effect of cold provocation on vessel density in eyes with primary open angle glaucoma: An optical coherence tomography angiography study

Vasoreactivity of the optic nerve head, nailfold, and facial skin in response to cold provocation in normal-tension glaucoma patients

BACKGROUND

The dysfunction of optic nerve head (ONH) hemodynamics has been suggested to be involved in the pathogenesis of normal-tension glaucoma (NTG). The aim of this study was to compare vasoreactivity in the ONH, nailfold, and facial skin in response to cold-water provocation in NTG patients and healthy controls.

METHODS

We performed cold-water provocation in 14 eyes of 14 NTG patients and 15 eyes of 15 age-matched control subjects. Laser speckle flowgraphy-derived tissue-area mean blur rate (MT), skin blood flowmetry-derived pulse wave amplitude (PA), nailfold capillaroscopy-derived nailfold capillary diameter, and other clinical parameters were recorded at baseline and 4 and 6 min after the cold stimulus. We compared changes (as percentages) in these variables in the NTG and control subjects with a linear mixed-effects model and evaluated correlations between these changes with Spearman's rank correlation coefficient.

RESULTS

The interaction term between the NTG group (reference, control group) and the 4-min protocol step (reference, baseline) significantly affected the changes in MT, nailfold capillary diameter and PA (β = -9.51%, P = 0.017, β = -20.32%, P = 0.002; β =  + 18.06%, P = 0.017, respectively). The change in MT was positively correlated with the change in nailfold capillary diameter, and negatively correlated with the change in PA (r = 0.39, P = 0.036; r = -0.40, P = 0.031, respectively).

CONCLUSION

NTG patients showed abnormal vasoconstriction in the ONH and nailfold and vasodilation in the facial skin in response to cold-water provocation.

Normal tension glaucoma: A dynamic optical coherence tomography angiography study

Purpose

Vascular dysregulation seems to play a role in the pathogenesis of glaucoma, in particular normal tension glaucoma (NTG). The development of optical coherence tomography angiography (OCTA) enabled the measurement of the retinal microvasculature non-invasively and with high repeatability. Nonetheless, only a few studies transformed OCTA into a dynamic examination employing a sympathomimetic stimulus. The goal of this study was to use this dynamic OCTA exam (1) to differentiate healthy individuals from glaucoma patients and (2) to distinguish glaucoma subcategories, NTG and high-tension primary open angle glaucoma (POAG).

Methods

Retinal vessel density (VD) in NTG patients (n = 16), POAG patients (n = 12), and healthy controls (n = 14) was compared before and during a hand grip test with a hydraulic dynamometer.

Results

At baseline, mean peripapillary VD was lower in POAG and NTG (42.6 and 48.5%) compared to healthy controls (58.1%; p < 0.001) and higher in NTG compared to POAG (p = 0.024) when corrected for mean arterial pressure (MAP). Peripapillary and macular (superficial and deep) VD differences were found for gender, age, and baseline MAP. No change in VD occurred (pre-/post-stimulus) in any of the groups.

Conclusion

Retinal VD loss in glaucoma patients was confirmed and the necessity to correct for gender, age and especially MAP was established. Although replication in a larger population is necessary, OCTA might not be the most suitable method to dynamically evaluate the retinal microvasculature.

Peripapillary vessel parameters and mean ocular perfusion pressure in young healthy eyes: OCT angiography study

BACKGROUND

To investigate the relationship between estimated mean ocular perfusion pressure (MOPP) and peripapillary perfusion density (PD) or vessel density (VD) as measured by spectral-domain optical coherence tomography angiography (OCTA) in young healthy eyes.

METHODS

132 healthy participants (264 eyes) under 45 years of age underwent optic disc OCTA scan sized 3×3 mm to acquire PD and VD in the superficial vascular complex (SVC). Optic nerve head (ONH) parameters including retinal nerve fibre layer (RNFL) thickness, rim area and disc area were measured. MOPP was estimated from systemic blood pressure and intraocular pressure (IOP). A linear mixed model was used to find the systemic and ocular factors associated with PD and VD.

RESULTS

The average age of the subjects was 25.8±6.5 years. PD and VD showed a significant correlation with RNFL thickness (r=0.224, p<0.001 and r=0.214, p<0.001, respectively), but with MOPP, the correlation was only marginally significant (r=0.105, p=0.09 and r=0.112, p=0.07, respectively). After controlling for confounding factors, including age, sex, IOP, central corneal thickness, axial length and OCTA signal strength, PD and VD were significantly associated with ONH parameters (all p<0.05) but not with estimated MOPP (all p>0.05).

CONCLUSION

PD and VD in the SVC were significantly associated with ONH parameters while showing no association with estimated MOPP. OCTA-derived VD may not represent perfusion pressure, but is rather more dependent on peripapillary structure.