Orbital injury causing blindness in a Thoroughbred horse.

The study presents an investigation into a case of orbital injury resulting in blindness in a Thoroughbred horse. A 5-year-old gelding, after experiencing a fall, showed significant orbital swelling and an absent menace response which prompted specialized treatment and exploration of intraocular changes, as well as journey on to assessing prognosis for vision restoration.

Incidence of Injury and Early Response

• The study recounts the incident of a 5-year-old Thoroughbred gelding horse who fell inside a float, causing serious injury to its left eye. This injury was significant enough to cause extensive swelling of the orbital and peri-orbital tissues.
• Immediate response to the injury included daily intravenous injections of 2.6g phenylbutazone sodium and 4.8g isopyrin, along with intramuscular injections of 6g procaine penicillin. The medication regimen continued for a week post-injury.
• After a week, when the swelling had finally subsided, but no significant response (menace response) could be elicited from the injured eye, a specialist was consulted.

Specialist Examination and Findings

• An ophthalmic examination was performed 10 days post-injury, which included testing by focal light, slit-lamp biomicroscopy, and direct and indirect ophthalmoscopy. The horse’s obstacle course performance was also evaluated.
• The examination revealed a condition called enophthalmos in the left eye, along with band opacities in the ventral cornea and stromal opacity in the limbal cornea. The left pupil was observed to be widely dilated and unresponsive to direct light.
• Other observations included a posterior subcapsular cataract presence in the left lens, discoloration indicating hyperpigmentation in the lateral tapetal fundus and peripapillary areas of the fundus.
• For some areas in the disk periphery, the retinal blood vessels were found to have narrowed, concealing the dorsal border of the optic disk and causing hemorrhages at the center of the disk.

Therapy Used and Final Prognosis

• Post-examination, an intramuscular injection of 25mg dexamethasone trimethylacetate was administered every five days, a total of three times. In addition, daily intravenous injections of 500 mg flunixin meglumine were given over five days.
• This was followed by oral administration of 13.5 g acetylsalicylic acid twice a day. The horse’s regimen was necessarily aggressive due to the severity of the injury and potential for lasting ocular damage.
• Despite diligent therapy, the prognosis remained gloomy for the horse’s vision restoration in the left eye. The injury turned out to be severe enough to cause permanent blindness.