A porcine model of selective retinal capillary closure induced by embolization with fluorescent microspheres.
OBJECTIVE
To investigate the feasibility of creating an animal model of selective retinal capillary closure to mimic the capillary closure that occurs in diabetic retinopathy.


METHODS
Fluorescent microspheres of 10- or 15-μm diameter were delivered to one eye of anesthetized pigs via a customized cannula advanced through the carotid arterial system to the origin of the external ophthalmic artery that supplies blood to the eye in this species. After preliminary trials in 10 pigs, embolization was performed in one eye of 34 animals that were allowed to survive for 7, 14, or 28 days. Embolized eyes were assessed by fluorescein angiography, electroretinography (ERG), and, after enucleation, light (LM) and electron (EM) microscopy.


RESULTS
The microspheres were detectable in the retina immediately after embolization, were restricted to the nerve fiber layer of the retina, and remained thereafter within the retina for periods up to 28 days. They effectively occluded embolized capillaries and some precapillary arterioles. No systemic or cerebral adverse effects were noted, thus allowing survival and subsequent follow-up. Embolization caused a reduction in the b-wave amplitude and the oscillatory potentials of the rod-cone bright-flash ERG but did not affect the amplitude of the a-wave. Embolization induced extracellular and intracellular edema confined to the inner and mid retina, and as a result the retinas of embolized eyes were thicker than those of fellow, nonembolized eyes. The outer retina and RPE were unaffected.


CONCLUSIONS
This survival model of retinal embolization with microspheres should be useful in the study of the retinal effects of the capillary closure that may occur in diabetic eyes.
Foulds
Wallace S
WS
Singapore Eye Research Institute, Singapore National Eye Centre, Singapore. wallace.stewart.foulds@seri.com.sg
Kek
Wee K
WK
Luu
Chi D
CD
Song
In Chin
IC
Kaur
Charanjit
C
D000818:Animals; D001160:Arterioles / Q000473:pathology; D002196:Capillaries; D003930:Diabetic Retinopathy / Q000209:etiology / Q000503:physiopathology*; D004195:Disease Models, Animal; D004596:Electroretinography; D004617:Embolism / Q000209:etiology / Q000503:physiopathology*; D005451:Fluorescein Angiography; D005456:Fluorescent Dyes; D000860:Hypoxia / Q000209:etiology; D007511:Ischemia / Q000209:etiology; D008269:Macular Edema / Q000209:etiology / Q000503:physiopathology*; D008863:Microspheres; D012161:Retinal Artery / Q000473:pathology*; D013552:Swine
D005456:Fluorescent Dyes