Common Eye Diseases of Horses

Written by kimberly hawthorne
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Common Eye Diseases of Horses
The eyes of horses are very susceptible to disease. (Horse Eye image by Alla Podkopaeva from

Horses have very large and sensitive eyes that can easily become inflamed due to a dust, an ailment such as the flu, or flying debris. Eye infections are common in horses and can be caused by conjunctivitis and other issues. Horses have two top eyelids that can both be affected by different types of tumours, while the cornea is highly susceptible to cataracts and other diseases.

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Corneal Ulcers

The cornea is the curved, clear part of the eyeball that covers the iris and pupil to protect them from dust and other debris. A corneal ulcer will show up as a milky patch or clouding of the cornea. Corneal ulcers can be caused by infection, poor blood circulation, nerve damage, trauma, nutritional imbalances and cancer. According to Go Pets America, this type of ulcer is an infected wound that can damage the horse's vision if left untreated. Symptoms include discharge and a build-up of pus in the corner of the eyelid. The cornea of the eye will appear cloudy and contain fine red lines. Corneal ulcers will generally respond to treatment but severe cases may require surgery to save the eye.

Equine Recurrent Uveitis (ERU)

Equine recurrent uveitis, also known as moon blindness, is the most common cause of blindness in horses. According to Go Pets America, the cause of uveitis is unknown as of 2010 but is believed to be due to a leptospires bacteria, as it is present in most known cases of this disease. Uveitis is believed to be very painful for the horse and should be treated by a veterinarian as soon as possible.


Entropion is a defect of the eyelid that causes it to roll upward. This upward rolling causes the eyelashes to rub on the cornea. This condition is mainly present in some newborn foals, although it can also occur in horses faced with severe dehydration. With foals, the eyelid should be sutured in a way that prevent the eyelid from rolling upward.

Neoplasia of the Lids

Eyelid melanomas are common in grey horses, as well as Arabians and Percherons. Melanomas are treated by surgical excision (removal) and cryotherapy (freezing). Sarcoids are neoplastic tumours of the eyelids and the periocular region of the horse. This type of tumour is caused by viruses, such as papilloma. The Blind Horses Organization says that flies may be able to transfer the viruses or the sarcoid cells from one horse to another.

Antipsoriasis skin ointments are used to shrink the sarcoid lesions prior to using other treatment options. Treatment options include: cryotherapy, hyperthermia, carbon-dioxide laser excision, intralsional chemotherapy and intralesional radiotherapy. In some cases, homeopathic ointments have been effective, according to the Blind Horses Organization.

Squamous Cell Carcinoma (SCC)

The most common eye tumour in horses is the squamous cell carcinoma (SCC). Occurrence of this type of tumour increases with age, it is also more common among Belgians, Clydesdales and other draft horses. Horses that are white, grey or palomino are more susceptible to SCC. Treatments for SCC include cryotherapy, immunotherapy, irradiation, radio-frequency hyperthermia or CO2 laser ablation following removal of the tumour.

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