Estimated reading time: 6 minutes
Subedited by Dr Phil Tucak
Roger was a two-year-old intact male Belgian Malinois that presented to Animal Eye Center (AEC) in Northern California, USA in August 2016 after experiencing a near miss gunshot to the left side of his face. Roger was working as a police dog for a nearby city, when he chased and apprehended a suspect, who shot at Roger at point-blank range. The bullet fortunately missed Roger but skimmed the left side of his face. The left eye was held closed, and mild haemorrhagic discharge was noted from the left eye when he was taken to the local veterinary clinic.
Examination at the primary veterinary clinic revealed blepharospasm, conjunctival hyperaemia, diffuse pinpoint corneal opacities with fluorescein stain uptake, corneal oedema and mild miosis. There were also erythema and superficial abrasions of the left periocular skin as well as the nasal bridge.
The left eye and face were flushed with copious amount of sterile saline, and his left eye was treated with topical triple antibiotic (bacitracin, neomycin, polymyxin B) ointment (q6h), topical atropine solution (q12h for two days then q24h), and carprofen 75mg (~2mg/kg) PO q12h for five days. An Elizabethan collar was recommended as needed to prevent self-trauma.
Roger was rechecked four days later. He seemed more comfortable with improved blepharospasm. Despite the Elizabethan collar, he was able to rub his face, which resulted in excoriation of the left side of his face. Multiple ulcers were still present, which prompted the referral to AEC. A larger Elizabethan collar was placed, and topical antibiotic was switched to ofloxacin prior to referral due to the handler having difficulty applying ophthalmic ointment.
On initial examination at AEC four days post incident, Roger was visual in both eyes, and the right eye was unremarkable. Intraocular pressures were 11mmHg in the right eye and 8mmHg in the left eye. There were multiple abnormalities of the left eye. There was a 2cm rim of periocular alopecia, erythemia and exudation as well as depigmentation and ulceration of the lid margins. Mild blepharospasm with moderate epiphora was present.
The pupil size was mid-range, fixed and isocoric to the right eye at room light despite atropine being applied eight hours prior. There was moderate conjunctival hyperaemia and chemosis. Multiple punctate gold-brown refractile foreign bodies were noted in the superficial to deep stroma, some of which were at 80% depth, with diffuse moderate corneal oedema.
These foreign bodies were presumed to be gunpowder fragments. The majority of the foreign bodies were epithelialised over, but there were three with pinpoint fluorescein uptake medial paraxially. There was 1+ aqueous flare. Posterior segment examination was limited due to anterior segment changes, but no abnormality was detected. Physical examination was otherwise unremarkable.
Smokeless gunpowder consists mostly of nitrocellulose. It is frequently combined with nitroglycerin and formed into small spheres, cylinders or flakes using solvents. These particles typically remain extracellular, have no toxic ocular effects and incite no inflammatory response. Thus, gunpowder particles are well tolerated in ocular tissues. The heat of the explosion and gunpowder particles, however, can cause ocular and periocular injury.
There is no large case series in human or veterinary literature in the English language. However, there have been a handful of human case reports of gunpowder injuries to the cornea, sclera, conjunctiva, vitreous, lens and retina. Almost all of the cases were managed conservatively with medications and had good outcomes.
If the gunpowder particles are superficial on the cornea and the conjunctiva, they can be removed to decrease the foreign body sensation. One case series written in Mandarin reported improvement in visual acuity with removal of gunpowder particles via phototherapeutic keratectomy (i.e. partial thickness ablation of the cornea using laser).
If the gunpowder particles are involving the retina or near it, it can be surgically removed to decrease the risk of retinal tear and detachment. It is worth noting that the gunpowder particles may not be radiopaque, so CT scans are considered superior to radiographs in identifying retained particles.
Given that Roger was only mildly uncomfortable and many of the fragments were in the deep stroma, conservative medical management was recommended rather than surgical removal of the gunpowder fragments. Treatments initiated by the primary veterinarian were continued for the left eye: topical ofloxacin q6h, topical atropine q12h, carprofen 75mg PO BID and continued use of an Elizabethan collar. In addition, topical hypertonic saline ointment (q6-8h) was started to reduce corneal oedema in the affected eye.
On recheck at AEC 11-days post incident, the skin and lid lesions had mostly resolved. The left eye was open and appeared comfortable during examination, but the handler reported mild squinting at home. Chemosis, conjunctival hyperaemia and corneal oedema had slightly improved. Multiple punctate gold-brown foreign bodies in the corneal stroma were unchanged and mild peripheral keratitis had developed, but there was no fluorescein stain uptake. Anterior flare had resolved. Intraocular pressure was 7mmHg compared to 16mmHg in the right eye.
At this stage, topical steroid (neomycin, polymycin B, and dexamethasone ointment q12h) was added to the treatment to treat conjunctivitis and keratitis. The other medications were tapered: ofloxacin q12h for one more week; atropine q24h for one more week; and carprofen 75mg PO q12h for one week, then q24h for one week. The Elizabethan collar was taken off, and Roger went back to duty with caution in case of some visual deficit in the left eye.
Two months post incident, Roger was comfortable in both eyes with no blepharospasm. Conjunctival hyperaemia and corneal oedema had resolved. No anterior flare was detected. Intraocular pressures were 13mmHg in both eyes. Other than multiple punctate stromal foreign bodies and some perilesional stromal fibrosis, Roger looked unremarkable, and all medications were discontinued. Roger showed no signs of visual impairment and had returned to full duty. The patient’s name has been changed but the case details and images are used with permission.
Dr Taemi Horikawa DVM, DACVO, MANZCVS.
Dr Taemi Horikawa is a veterinary ophthalmology specialist currently practising at Perth Animal Eye Hospital.
Dr Horikawa has special interests in anterior segment imaging and glaucoma surgeries and is thrilled to be able to offer her experiences in ultrasound biomicroscopy, Ahmed gonioshunts and endoscopic cyclophotocoagulation to the WA veterinary community.
Prior to being convinced by her now husband to relocate to his native land Perth in 2018, Dr Horikawa completed her veterinary education at UC Davis, followed by a small animal rotating internship and a three-year comparative ophthalmology residency.
After her board certification, Dr Horikawa practised in Northern California, where she also enjoyed opportunities to provide ophthalmic care to local rescue groups and teach interns.