A Hidden Cause of Blindness: First Report of a Plant Foreign Body in the Optic Nerve

Magnetic Resonance Imaging and Histopathology of an Optic-Nerve Plant Foreign Body in a Dog

M. M. Dyrka, G. Hammond, G. Pepliński, E. Scurrell, S. Aarsvold, M. Pasierbińska, R. Gutierrez-Quintana, A. Kaczmarska

Background

Intraocular foreign bodies are uncommon but can result in severe inflammation and vision loss. Plant foreign bodies are known to migrate through tissues; however, involvement of the optic nerve has not previously been reported. This case report describes the clinical presentation, magnetic resonance imaging (MRI) findings, and histopathological features of a plant foreign body embedded within the optic nerve of a dog.

Methods

A one-year-old neutered female Labradoodle presented with a 24-hour history of lethargy and head tilt. Ophthalmic examination revealed bilateral third-eyelid protrusion, enophthalmos, blepharospasm, conjunctivitis (more severe in the right eye), intermittent right-sided head tilt, and right ventral positional strabismus. Progressive findings included right uveitis, iris oedema, pre- and intra-retinal haemorrhages around the optic nerve, and elevated intraocular pressure, while vision initially remained intact.

Bloodwork, cerebrospinal fluid (CSF) analysis, CSF culture, and infectious-disease screening were unremarkable. MRI identified partial retinal detachment, thickening of the right optic nerve, hyperintensity of the extraocular muscles on FLAIR sequences, and contrast enhancement of the sclera and iris, consistent with inflammatory disease of the globe and periocular tissues. The plant foreign body was not definitively identified on MRI.

Following progression to blindness despite treatment with marbofloxacin and prednisolone, enucleation was performed. Vitreous cytology suggested bacterial infection. Gross examination revealed a thin (~10 mm), linear plant fragment within the vitreous chamber. Histopathology confirmed a plant material fragment embedded within the optic nerve, associated with suppurative bacterial endophthalmitis, retinal detachment, and secondary glaucoma.

Results

MRI findings supported severe inflammatory involvement of the globe and optic nerve but did not definitively identify the foreign material. Histopathology demonstrated a thin linear plant fragment embedded in the optic nerve head and optic nerve, surrounded by pyogranulomatous inflammation. The ocular pathology included suppurative bacterial endophthalmitis, retinal detachment, and secondary glaucoma.

Clinical signs such as intermittent head tilt and positional ventral strabismus were interpreted as adaptive responses to optimize vision and reduce discomfort.

Limitations

This report describes a single case, limiting generalizability. The plant foreign body was not conclusively visualized on MRI, highlighting the limitations of imaging in detecting small organic foreign material. The route of migration was not definitively established.

Conclusions

This case documents the first reported instance of plant material embedded within the optic nerve of a dog. MRI findings suggested severe inflammatory ocular disease but were insufficient to definitively identify the foreign body. Histopathology was essential for diagnosis. Clinicians should consider migrating plant foreign bodies as a differential diagnosis in cases of acute unilateral uveitis, optic nerve thickening, and progressive vision loss, even when advanced imaging fails to identify a discrete foreign object.

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