Ocular lesions following suspected lightning injury in a horse.

In simple terms, this study describes the unusual eye damage found in a two-year-old racehorse after it was suspected to be struck by lightning. This damage was only discovered after the horse was put down due to vision problems.

Methods: Examining the Eyes

• The researchers conducted a thorough examination of the horse’s eyes after it had been euthanized. This happened after a heavy lightning storm, and the horse had shown signs of visual impairment.

Results: Notable Findings

• Starting off, they noted severe corneal edema and hydrops in the right eye. Corneal edema refers to the swelling of the cornea, while hydrops are sudden, intense swelling or the entrance of fluid into the cornea.
• Using indirect ophthalmoscopy, they identified unusual, symmetrical lesions around the periphery of the optic disc in both eyes. These lesions were described as being “hyporeflective,” meaning they appeared darker than the surrounding tissue.
• The pathological examination of the horse’s eyes further revealed that despite the severe corneal edema in the right eye, the corneal endothelium (the thin layer of cells lining the inner part of the cornea) was normal.
• Upon evaluating the posterior segment of the eyes, they found distinct lesions in the choroid, a vascular layer of the eye situated between the retina and the sclera. These lesions were characterized by haemorrhage, early fibrosis (the formation of excess fibrous tissue), and minimal inflammation and proliferation from various cells including lymphoplasmacytic cells, neutrophils, and histiocytes.
• The researchers also noted that the retinas overlying these choroidal lesions were mostly absent and had gone necrotic, descriptive of tissue death caused by insufficient blood supply, infection, or toxin exposure.
• On the periphery of the main lesion, the retinal architecture abruptly returned to normal, however, an area filled with dying photoreceptor cells (the cells in the retina that respond to light) was observed.
• In the central region, there were swollen axons (nerve fibres) extending into the optic disc.

Conclusions: A Unique Instance

• The investigators pointed out that there are very few recorded instances of animals developing ocular lesions following a suspected lightning injury, making this case unique.
• The type of thermal injury observed is believed by the researchers to be characteristic of a lightning strike injury, although they could not definitively confirm this. More information about how these lesions might have progressed over time, had the horse not been euthanized, also remains unknown.