Measuring hyperemic response to light flicker stimulus using continuous laser speckle flowgraphy in mice

A Period of Macular Hyperemia and Subclinical Edema Caused by Phacoemulsification Surgery in Noninfectious Uveitis

PURPOSE

To identify the changes in macular microvasculature in uveitic patients following phacoemulsification.

METHODS

A prospective cohort study was conducted by enrolling uveitic patients who underwent phacoemulsification at the Eye Hospital. Macular vessel densities (VD) of superficial and deep capillary plexus (SCP and DCP) and retinal thickness (RT) were quantified by optical coherence tomographic angiography (OCTA).

RESULTS

Twenty-one eyes obtained satisfactory OCTA scans at all the follow-up visits. After surgery, an increasing trend in SCP VD was found (p = .037) and reached its maximum (+2.79 ± 4.86%) at post-3 months (M). RT increased synchronously. The increases in SCP VD at post-3 M were significantly correlated with the changes in anterior chamber cells (ACCs) at post-1 M and 2 M (r = 0.450, p = .041; r = 0.477, p = .029, respectively).

CONCLUSIONS

Inflammation generates a long-term effect on retina demonstrated as an increase in SCP VD and RT which are associated with synchronous ACCs changes after phacoemulsification.

Mouse model of radiation retinopathy reveals vascular and neuronal injury

PURPOSE

To characterize the neuronal and vascular pathology in vivo and in vitro in a mouse model of radiation retinopathy.

METHODS

C57Bl/6J mice underwent cranial irradiation with 12 Gy and in vivo imaging by optical coherence tomography and of relative blood flow velocity by laser speckle flowgraphy for up to 3-6 months after irradiation. Retinal architecture, vascular density and leakage and apoptosis were analyzed by histology and immunohistochemistry before irradiation or at 10, 30, 240, and 365 days after treatment.

RESULTS

The vascular density decreased in the plexiform layers starting at 30 days after irradiation. No impairment in retinal flow velocity was seen. Subtle perivascular leakage was present at 10 days, in particular in the outer plexiform layer. This corresponded to increased width of this layer. However, no significant change in the retinal thickness was detected by OCT-B scans. At 365 days after irradiation, the nuclear density was significantly reduced compared to baseline. Apoptosis was detected at 30 days and less prominent at 365 days.

CONCLUSIONS

By histology, vascular leakage at 10 days was followed by increased neuronal apoptosis and loss of neuronal and vascular density. However, in vivo imaging approaches that are commonly used in human patients did not detect pathology in mice.

Methods to measure blood flow and vascular reactivity in the retina

Disturbances of retinal perfusion are involved in the onset and maintenance of several ocular diseases, including diabetic retinopathy, glaucoma, and retinal vascular occlusion. Hence, knowledge on ocular vascular anatomy and function is highly relevant for basic research studies and for clinical judgment and treatment. The retinal vasculature is composed of the superficial, intermediate, and deep vascular layer. Detection of changes in blood flow and vascular diameter especially in smaller vessels is essential to understand and to analyze vascular diseases. Several methods to evaluate blood flow regulation in the retina have been described so far, but no gold standard has been established. For highly reliable assessment of retinal blood flow, exact determination of vessel diameter is necessary. Several measurement methods have already been reported in humans. But for further analysis of retinal vascular diseases, studies in laboratory animals, including genetically modified mice, are important. As for mice, the small vessel size is challenging requiring devices with high optic resolution. In this review, we recapitulate different methods for retinal blood flow and vessel diameter measurement. Moreover, studies in humans and in experimental animals are described.