Abstract
Purpose :
To quantitatively compare the effect of elevated intraocular pressure (IOP) on retinal and choroidal blood perfusion between male and female rats using swept source optical coherence tomography angiography (SS-OCTA).
Methods :
The IOP of male and female (2-month-old, n=8 per group) Brown Norway rats was elevated in 10 mmHg increments from 10 to 100mmHg. At each IOP level, 3D OCT datasets were captured with a novel 1.3 μm SS-OCTA prototype system using an optical microangiography (OMAG) scanning protocol to obtain microangiograms of the posterior eye in vivo with resolution at the capillary level. The perfused microvasculature within the retina and choroid were segmented and the functional vessel density was quantitatively measured at each IOP level. The vascular area density (VAD) index, defined as the ratio of area occupied by functional blood vessels to the total scan area, was calculated for the retina excluding large vessels >30 μm, and for the choroid after the retinal tailing artifacts removed. Changes of VAD vs IOP were plotted for the group means and compared between males and females.
Results :
Mean arterial blood pressure (MAP) in male and female animals was 91±10 mmHg (mean±SD) and 85±11 mmHg, respectively (n=8 per group), 10 mmHg lower than in 6–8 months old rats. Volumetric blood flow reconstructions after segmentation revealed blood perfusion maps, to the capillary level, for the retina and the choroid/sclera. Shown are the representative results at selected IOPs for male (A) and female (B) rats. From the angiograms and the VAD analysis, the blood vessel filling in both the retina and choroid were not affected by moderate increase in IOP up to 40 mmHg, beyond which the filling density decreased, with retinal VAD reaching 50% of baseline at 50 mmHg, whereas choroidal VAD reaching 50% of baseline at 60 mmHg. They were both nearly extinguished at 70 mmHg. No significant gender differences were observed in the responses of retinal and choroidal blood perfusion to IOP changes. In both sexes, posterior ciliary arteries were clearly identified at 60 mmHg and appeared unaffected at higher IOPs.
Conclusions :
SS-OCTA/OMAG enables quantitative comparisons of the response of retinal and choroidal perfusion to changes in IOP. In both males and females, reduction of choroidal filling is delayed in comparison with retinal perfusion upon IOP elevation.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.