Ocular Diseases

Anophalmia/Micropthalmia

Globe is absent or much smaller than normal, usually associated with a combination of defects, uni or bilateral

Aniridia

Complete absence of the iris, reported in quarter horses and belgians, usually bilateral, occurs with photophobia and blepharospasms, congenial thinning of iris or cull thickness hole in it

Hypoplasia

Iris is present but more thin, appears more white

Anterior Segment Dysgenesis in Rocky Mountain Horses

Whole front portion of the eye has a problem, in Rocky Mountain Horses

Congenital/Hereditary Nuclear Cataract

Most common congenital defect of the eye in foals, in herited in belgians and morgans, typically bilaterally and non-progressive, treatment: nothing - may be safe if not super affected, phacoemulsification - go in and replace with new lens in lens capsule, vision aids to manage

Congenital Stationary Night Blindness

Serious defect, normal vision in light, diminished vision in darkness, more prone to injuries and getting anxious in diminished light, no treatment, but management by containing them in the evenings and giving them light to help, diagnosed by electroretinography

Dermoid

Normal skin in the incorrect place, size and degree of irritation determines if it needs removed, can cause corneal abrasion

Heterochromia

Different colored irises, could be more light sensitive, not uncommon to see less pigmentation of structure in grey/blue equines

Hypertrophy of the corpora nigra

Common, where corpora nigra is enlarged, may be large without affecting vision

Iris Stromal Cysts/Iridal Cysts

Iris gets cysts that don’t cause pain but can cause vision impairment, hang into the pupil, usually contain clear fluid that can rupture spontaneously, treatment is lasering and it pops them, can be a part of ASD syndrome

Nasolacrimal System Atresia

Nasolacrimal duct that is blocked/doesn’t work properly, uni or bilateral, signs: initial mucoid discharge (1-2 yrs old), may become copious and often mucopurulent, diagnosed by dacryorhinocystography, treatment is surgery to create new NL duct

Neonatal Maladjustment Syndrome/Hypoxic Ischemic Encephalopathy

When foal doesn’t get enough oxygen supply during birth, condition presents with other severe abnormalities like retinal and optic nerve hemorrhages, corneal edma, asymmetric pupils, corneal erosion

Trauma

In the orbit, most common cause of orbital disease, fractures of bony orbit (takes surgical repair is bones displaced), foreign body entry, rupture of globe. Signs: Exo/Enopthalmos (Eye is sunken in or protruding) Lid/conjunctival swelling, decreased ocular mobility, strabismus, 3rd eyelid elevation (protruding). Diagnosed by palpation and/or radiographs

Neoplasia

Primary or metastatic, tumors in the orbit

Extension of Disease from Other Tissues

In the orbit, bacterial or fungal infections, can include sinuses, guttural pouches, teeth, etc.

Ectropion

When the eyelid is turned inside out, often secondary to chemosis

Entropion

When the eyelid is turned in towards the eye and eyelashes hit cornea, common in foals (Premature/dysmature, malnourished, dehydrated). Treatment for mild cases is frequent manual correction of lid and topical antibiotic ointments, treatment of severe cases is application of superglue, local anesthetic injected into lower lid, vertical mattress sutures to temporarily hold lid in

Eyelid Lacerations

Often associated with itchy head or uncomfortable halter/cribbing strap, usually happens to upper more often than lower lid and result is a small to large lid defect. Lower may affect drainage of tears into NL duct, can lead to corneal damage if not repaired. Treat with systemic NSAIDS IMMEDIATELY, every attempt made at surgical repair and never trim off any tissue even if it looks dead

Cutaneous Habronemiasis

Summer problem, house/stable flies carrying habronema infective larva deposit them into a wound/moist areas around the eye. Larva don’t develop but dying micofilia cause inflammatory reaction. Signs: Area is itchy, nonhealing lesion with yellowish gritty material, lesion has a “meaty” appearance. Diagnosis based on location, time of year, clinical signs, biopsy/histology. Treatment: Oral ivermection or moxidectin (topical dewormer if severe), corticosteroid drops/ointment, systemic NSAIDS

Sarcoid

Most common tumor of horses in general, appears as mass around eye, enlarges progressively and slowly, diagnosed by histology from biopsy, treatment: lesion debulked and immunotherapy/cryotherapy/chemo, hyperthemia, laser excision, X-terra, antipsoriasis skin ointments, may need several treatments

Squamous Cell Carcinoma

Most common eyelid tumor, shows up more in geldings, locally aggressive, pink skin around eye, appy’s and draft breeds hereditarily, signs: ulcerative lesion around lid margins and non-pigmented skin, diagnosis: signs and biopsy + histopathology, treatment: surgery (excision has most sucess), extensive involvement of eye = remove whole eye, immunotherapy/cryotherapy/chemo, hyperthermia

Melanoma

Mostly in grays, may metasize to internal organs, treatment: wide surgical excision, cryosurgery, laser therapy, antineoplastic drugs (cisplastin, imiquamod), cimetidine (oral) helps some horses

Conjunctivitis

May accompany a wide variety of ocular and non-ocular conditions, summer + dust + flies predispose, viral respiratory infections, pruritus, allergies or irritants in the air, unilateral OR bilateral, diagnosis: mucopurulent ocular discharge, inflamed conjunctiva, do flurescein stain just to be sure, treatment: treat underlying cause, moistened gauze sponges to remove purulent material, if no ulcer - okat to use opthalmic steroid ointment/drops. ALWAYS FIRST THINK IF THEY HAVE UVEITIS EVEN IF IT DOESN’T LOOK BAD

Chemosis

Acute swelling of conjunctiva due to flies, dust, ocular trauma, subconjunctival hemorrhage, chemical irritation (shampoo), inflammation of uvea, treatment: treat underlying problem, topical hot compress, hyperosmotic ointments, topical antibiotics to prevent infection

Corneal Ulcerations

Happen often, vision threatening, break in corneal epithelium, may be slow to heal and likely to become infected, early diagnosis → appropriate treatment → and careful monitoring = essential, caused by trauma, conjunctival hyperemia, possible 2ndary anterior uveitis, diagnosis: fluorescein stain, gram and giemsa stain, corneal swab on blood agar plate for bacterial c and s. treatment (uncomplicated): within 1-2 days, broad-spectrum antibiotic ointment, atropine until pupil dilates and then as needed (to help paralyze ciliary muscle and help with painful spasms) but be careful bc too often can cause colic, NSAIDS. treatment (complicated): can take 6-8 weeks, atropine until complete mydriasis, use of antibiotic, autologous serum, anticollagenase - to prevent stromal melting, keep in dark stall, NSAIDS, DON’T GIVE CORTICOSTEROIDS BECAUSE THEY CAN INCREASE CHANCE OF FUNGAL/BACTERIAL INVASION

Descemetocele

EXTREME EMERGENCY!!! Corneal ulceration that has gotten to descemet’s membrane, very close to rupture of eye and internal structure of eye, will need conjunctival flap to provide physical support, blood vessels to carry fibroblasts and immunologic defense factors, 2 types of surgery: Perilimbal lesion (fornix-based flap) or central lesion (pedicle or bridge flap)

Corneal Stromal Abscess

Corneal ulcer that gets infected and heals infection in under epithelium, likely to be fungal not bacterial, epithelial barrier protects organisms from meds and tests. Signs: photophobia, lacrimation, blepharospasm, yellow-white stromal infiltrate, corneal edema, deep corneal vascularization, ± anterior uveitis. Diagnosis: Fluorescein stain neg. bc of intact epithelium, corneal scraping (cytology, c and s), fungal culture. Therapy: 3-6 weeks, intermittent corneal debriding of epithelium, SPL system, treat until vascularization is gone. SUrgery: Penetrating keratoplasty (PK) or posterior lamella keratoplasty (PLK) - takes weeks to resolve and likely leave corneal scar