Choroidal Vasculature Changes in Spontaneously Hypertensive Rats – Transmission Electron Microscopy and Scanning Electron Microscopy with Casts

Purpose: The purpose of the present study was to elucidate the specific morphological changes of the choroidal vasculature in long-term hypertension. Methods: The choroidal vessels of spontaneously hypertensive (SHR) rats were examined with corrosion casts/scanning electron microscope (SEM) and the transmission electron microscope (TEM). Results: In 18-month-old SHRs, corrosion casts and SEM showed tortuosity, caliber irregularity and generalized narrowing of the choroidal arteries. The draining venules were prominently decreased in number. The ampullae of the vortex veins were narrow, but arteriovenous anastomoses, crossing defects and obstruction were not seen. The choriocapillaris was elongated and engorged. TEM of the choroidal vessels showed hypertrophy of smooth muscle cells and irregular thickening of the basement membrane and narrow lumen of the choriocapillaris. The RPE and Bruch’s membrane were intact. Conclusion: The choroidal vascular bed showed extensive morphological changes. This study revealed that hypertensive choroidopathy has specific features such as tortuosity, caliber irregularity, generalized narrowing of arteries, decreased number of draining venules and elongated and engorged choriocapillaris. These findings indicate that hypertensive choroidopathy is as important as retinopathy.