Angiography and multifocal electroretinography show that blood supply to the pig retina may be both ipsilateral and contralateral.

PURPOSE: We recently presented a transfemoral endovascular coiling technique for inducing experimental retinal ischemia in pigs. Substantial variation was seen in the degree of ischemia. It was hypothesized that the blood supply to the retina may originate from both the ipsilateral and contralateral ophthalmic arteries and that there may be an interconnecting artery between the eyes. METHODS: The external carotid system of 6 pigs was catheterized using a fluoroscopy-monitored, transfemoral, endovascular approach. Vascular occlusion was achieved in the ophthalmic artery using coils. The effect of occlusion was examined using angiography and multifocal electroretinography (mfERG). RESULTS: During angiography of the ophthalmic artery on one side, contrast filling was seen in the retinas on both sides, suggesting that the ophthalmic artery on one side may supply both retinas. A blood vessel connecting the eyes was visualized. The mfERG recordings indicated that the use of coiling to occlude the ophthalmic artery had greater ischemic effects in eyes that may depend mainly on the ipsilateral ophthalmic artery for blood supply and had smaller ischemic effects in retinas that received blood from both the ipsilateral and contralateral ophthalmic arteries via the interconnecting vessel. CONCLUSIONS: The blood supply to the retina may originate from both the ipsilateral and contralateral ophthalmic arteries in the pig. There is an interindividual variability in the ischemic effect of occlusion depending on the architecture of the vasculature. These findings may be important in the development of new animal models of experimental retinal ischemia because arterial occlusion in one eye may affect the blood supply to the contralateral eye.

Endovascular coiling of the ophthalmic artery in pigs to induce retinal ischemia.

PURPOSE: The authors recently showed that the retinal circulation can be accessed by transfemoral endovascular catheterization. The purpose of this study was to examine whether endovascular coiling can be used to induce different degrees of ischemic injury. The possibility of creating occlusions at different sites in the vasculature to cause retinal ischemia with different degrees of severity was investigated. METHODS: The ophthalmic artery was catheterized through the external carotid system using a fluoroscopy-monitored, transfemoral, endovascular approach in 12 pigs (mean weight, 70 kg). The effects were evaluated using angiography and multifocal electroretinography. RESULTS: Occlusion of arteries supplying the retina was established using endovascular coiling. Coiling in the proximal part of the ophthalmic artery caused no or little ischemia, presumably because of collateral blood supply. Coiling in the distal part of the ophthalmic artery, over the branching of the main ciliary artery, caused more severe retinal ischemia. Multifocal electroretinography recordings, which reflect retinal function in an area close to the visual streak, showed decreased amplitudes and increased implicit times after distal occlusion, but not after proximal occlusion of the ophthalmic artery. The responses were similar 1 hour and 72 hours after coiling, indicating that a permanent ischemic injury was established. CONCLUSIONS: The porcine ophthalmic artery can be occluded using an endovascular coiling technique. This provides an experimental animal model of retinal ischemia in which occlusion at different sites of the vasculature produces different degrees of severity of the ischemic damage.

Multifocal electroretinogram for functional evaluation of retinal injury following ischemia-reperfusion in pigs.

BACKGROUND: Multifocal electroretinogram (mfERG) has the power to discriminate between localized functional losses and overall retinal changes when evaluating retinal injury. So far, full-field ERG has been the gold standard for examining retinal ischemia and the effects of different neuroprotectants in experimental conditions. The aim of the present study was to establish mfERG, with simultaneous fundus monitoring, for analyzing the localized functional response in the retina after ischemia-reperfusion in the porcine eye. METHODS: 70 kg pigs underwent pressure-induced retinal ischemia (1 hour) followed by reperfusion. mfERG recordings were obtained before and after ischemia, followed by 1 and 5 hours of reperfusion. Individual components of the summed mfERG responses were correlated to ischemia and the time of reperfusion. RESULTS: The visual streak area had significantly higher amplitudes than the optic nerve head and the area in between, suggesting that the mfERG monitors localized functional retinal responses. The mfERG recordings were altered following ischemia-reperfusion. In one group of animals, there was a complete flattening of the mfERG waveforms, indicating complete ischemic injury. In the other group of animals, ischemia-reperfusion altered the mfERG such that the implicit time was increased (20.82 +/- 0.18 before ischemia and 21.57 +/- 0.21 after ischemia and 1 hour of reperfusion, in the visual streak area, p < 0.05) and the amplitude was decreased (13.16 +/- 2.3 before ischemia and 11.47 +/- 0.88 after ischemia and 1 hour of reperfusion, in the visual streak area, p < 0.001), suggesting partial ischemic injury. CONCLUSIONS: In conclusion, the porcine model of pressure-induced retinal ischemia-reperfusion results in mfERG changes, typical for retinal ischemia. mfERG may be a useful tool for evaluating and monitoring localized cone dysfunction after an ischemic injury.

Riboflavin and ultraviolet a collagen crosslinking of the cornea for the treatment of keratitis.

PURPOSE: To describe riboflavin and ultraviolet light (UV) collagen crosslinking as an effective treatment for infectious keratitis. METHODS: A 25-year-old previously healthy female contact lens user was diagnosed with unilateral severe keratitis with unclear pathogenesis, although the clinical presentation suggested acanthamoeba as the infectious agent. A 4-mm diameter, annular, semi-opaque infiltrate was found on the paracentral parts of the cornea in the left eye (OS). Laboratory examinations for bacteria, herpes simplex, and acanthamoeba were performed, but no specific pathogen could be detected. Best corrected visual acuity (BCVA) at presentation was 20/1000. Treatment was initialized with broad-spectrum antibiotics also covering acanthamoeba. During the first month of treatment the keratitis progressed and the corneal thickness diminished. Therefore, treatment with riboflavin and UV collagen crosslinking was initiated. RESULTS: After riboflavin and UV collagen crosslinking therapy, there was a rapid decrease of pain and necrotic material. Reepithelialization of the cornea started within a few days and was complete within a month. After 2 months, the wound had healed completely. Nine months after the UV treatment, BCVA was 20/30. CONCLUSIONS: This case illustrates the positive effects of riboflavin and UV collagen crosslinking on presumed infectious keratitis with a satisfactory final visual outcome. This may be a promising new treatment for keratitis, although this remains to be elucidated in detail in future studies. Until more data are available this treatment should only be considered in therapy-refractive keratitis or ulceration and not in the first line of defence since it may have cytotoxic side effects.

The porcine retinal vasculature accessed using an endovascular approach: a new experimental model for retinal ischemia.

PURPOSE: The aim of this study was to examine whether the retinal circulation in the pig can be accessed using interventional neuroradiology and to explore the possibility of creating occlusions that result in experimental retinal ischemia. METHODS: Six experiments were performed using 100-kg pigs. The external carotid system was catheterized using a fluoroscopy-monitored, transfemoral, endovascular approach. Transient and permanent vascular occlusions were performed using an angioplasty balloon catheter or a liquid embolic agent that was administered via an injection-catheter. RESULTS: A technique for transfemoral catheterization of arteries supplying the retina was established. The ophthalmic artery was demonstrated to give rise to the main ciliary artery from which the retinal artery branched as a single artery or as several arteries. A balloon-catheter could be introduced into the ophthalmic artery but not into the main ciliary artery. An injection-catheter could, in all experiments, be introduced into the main ciliary artery and, in some experiments, into the retinal artery. Occlusion of the ophthalmic artery, over the branching of the main ciliary artery, caused incomplete ischemia, presumably because of collaterals feeding the distal parts of the vasculature. Multifocal ERG (mfERG) recordings showed decreased amplitudes and increased implicit times, indicating retinal ischemia. Occlusion of the ciliary and retinal arteries caused complete ischemia, as shown by complete flattening of the mfERG recordings and, by indirect ophthalmoscopy, blanching of the retinal arteries and a pale retina, CONCLUSIONS: The authors show for the first time that the ophthalmic and retinal artery can be catheterized using a transfemoral endovascular approach. This technique may be useful to produce clear-cut experimental retinal ischemia.