Retinal and corneal toxicity analysis of different intraocular injection methods of foscarnet sodium in rabbit eyes

Objective  To evaluate the toxicity of foscarnet sodium injection into the anterior chamber and intravitreal cavity on the cornea and retina.

Methods  Thirty-six adult New Zealand White rabbits were randomly divided into control group, intravitreal injection group, and intracameral injection group, with 12 rabbits in each group.In the control group, 0.1 ml of balanced salt solution (BSS) was injected into the vitreous cavity of one eye, and an equal volume of BSS was injected into the anterior chamber of the other eye.In the intracameral injection group and intravitreal injection group, 0.1 ml of sodium foscarnet 1.2 mg was injected into the anterior chamber and vitreous cavity of one eye, respectively.Slit-lamp microscopy, ophthalmoscope, optical coherence tomography (OCT), and in vivo confocal laser scanning microscopy were performed on 3 experimental rabbits from each group on days 1, 7, 14, and 28 after injection.After sacrifice, both eyeballs were removed, and the corneas and retinas were examined using optical microscopy, scanning electron microscopy and transmission electron microscopy to evaluate the toxicity to the cornea and retina comprehensively.The use and care of the animals complied with the ARVO Statement.The study protocol was approved by an Ethics Committee of Peking University Third Hospital (No.IRB00006761-2015197).

Results  Slit-lamp microscopy and OCT showed no corneal edema, intraocular inflammation, or other abnormalities in the intravitreal injection and control groups.Mild corneal edema was observed in intracameral injection group 1 day after injection, which resolved 7 days after injection. In vivo confocal laser scanning microscopy revealed normal hexagonal corneal endothelial cell morphology in the intravitreal injection and control groups.There was no significant difference in endothelial cell density at baseline and 1, 7, and 14 days after injection among the three groups ( F _group=1.21, P=0.32; F _time=1.21, P=0.32).Light microscopy revealed no obvious corneal abnormalities.On days 1 and 7 after injection, retinal nerve fiber layer vacuolization and inflammatory cell infiltration were observed in the intravitreal injection and control groups.In the intravitreal injection of BSS group, inflammatory cell infiltration occurred in the retina without vacuolization 1 day after injection.There were no structural changes in the photoreceptor layer, and the nuclear layer was well-organized.Scanning electron microscopy showed no significant abnormalities in the corneal endothelium in the intravitreal injection group 1 day after injection.In the intracameral injection group, a large number of inflammatory cells were deposited and adhered to the corneal endothelium 1 day after injection and disappeared 7 days after injection.Transmission electron microscopy revealed that in the intravitreal injection group, 1 day after injection swelling of corneal endothelial cells, dilatation of the endoplasmic reticulum, and partial mitochondrial swelling were observed, which normalized 14 days after injection and vacuolization was present in the retina and interstitial fluid accumulation persisted until the 28 days after injection.In the intracameral injection group, swollen mitochondrial and endoplasmic reticulum of corneal endothelial cells was observed and resolved by 14 days after injection.However, structural abnormalities in the membranous discs of the photoreceptor outer segments and interstitial fluid accumulation in the optic nerve fiber layer persisted 1 day after injection and did not fully recover 28 days after injection.

Conclusions  Intracameral intravitreal and injection of foscarnet sodium have transient toxic effects on the retina, which gradually weaken over time.Intracameral injection of foscarnet sodium was more toxic to corneal endothelial cells than intravitreal injection.

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