This horse sustained a traumatic injury to the outer edge of the third eyelid on the right eye. Although the surface of the eye was not damaged the lacerated portion of the third eyelid started to protrude outside the upper eyelid resulting persistent irritation to the horse and disruption to normal blinking function.
The decision was made to remove the entire third eyelid. The horse was treated at the clinic as an out-patient and the procedure was performed with in the stocks under intravenous sedation. Specific nerve blocks were placed around the eye to remove the motor innervation to the upper eyelid and sensory innervation to the inside corner of the eye to allow the procedure to be performed. Fluorosien dye was placed over the cornea to check for damage to its surface. This dye is orange on application and turns bright green on contact with the cornea. Defects in the surface of the cornea are outlined by this stain and allow accurate identification of damage that may be otherwise undetectable with an ophthalmoscope. Following additional topical local anaesthetic, the third eyelid was grasped using fine ophthalmic forceps. Protraction revealed the full width of the cartilage flap which gives the third eyelid its rigidity.
Haemostatic clamps were placed behind the cartilage flap within the soft mucosa before a small scapel blade was used to resect the third eyelid.
This was an unusual case of ocular trauma. The more common reason for third eyelid removal is the appearance of infiltrative masses such as squamous cell carcinomas. These tumours are locally invasive and early removal if recommended so that wide margins can be achieved. When third eyelids are removed because of mass formation they are always sent to the laboratory for histopathological examination to identify the type of mass present and confirm its complete excision.