Complete ophthalmic examination in the horse generally requires sedation and an auriculopalpebral nerve block.
Before sedation, the symmetry of the head and globes are examined followed by evaluation of the menace response and palpebral reflex.
After sedation and akinesia of the auriculopalpebral nerve, the adnexal structures, cornea, and pupillary light reflexes are examined.
Diagnostics, including fluorescein staining, cytology, culture, Schirmer tear test, and tonometry, are often indicated at this time. The examination is continued with evaluation of the anterior segment, mydriasis, and indirect and direct ophthalmoscopy. Subpalpebral lavage systems are often required for the treatment of painful corneal conditions. Subpalpebral lavage systems are relatively easy to place and are relatively problem-free if maintained properly.
- To perform the menace reflex, the examiner abruptly moves a hand toward the horse's eye. The appropriate response is to blink the eye, and perhaps move the head away. This helps us to determine if your horse can see.
- To perform the palpebral reflex, the examiner lightly touches the eyelid, and the horse should close his eye. This helps to determine if the horse has skin sensation, and if he has control of the muscles of the face.
- To perform the pupillary light reflex, the examiner brings the horse into dim lighting, and shines a penlight first into one eye, then the other. The pupils of the eye should constrict. This helps to assess pathways in the brain that control eye function.
Diseases of the equine eye
- Recurrent uveitis
- Keratomycosis - fungal eye infection
- Keratoconjunctivitis sicca - dry eye
- Congenital stationary night blindness
- Ocular squamous cell carcinoma
- Corneal ulcer
Breed specific diseases
|Appaloosa||Ocular Squamous cell carcinoma, Congenital stationary night blindness (CSNB), Congenital cataract, Glaucoma, recurrent uveitis, Optic disc colobomas|
|Belgian draft horse||Aniridia and secondary cataract|
|Morgan||Cataract - nuclear, bilateral, symmetrical, and non-progressive|
|Quarter horse||Congenital cataract, entropion|
|Rocky mountain horse||Anterior segment dysgenesis, congenital miosis, and corpora nigra and iris hypoplasia, macrocornea, ciliary cysts, cataract, lens luxation, retinal dysplasia, retinal detachment|
|Thoroughbred||Congenital cataract, microphthalmia associated with multiple ocular defects, retinal dysplasia associated with retinal detachments in some cases, entropion, progressive retinal atrophy|
|Standardbred||Retinal detachments, congenital stationary night blindness|
|Paso fino||Congenital stationary night blindness, glaucoma|
|American saddlebred||Cataract, keratomycosis|