Fig. 11. Corneal abrasion indicated by faint fluorescein staining occurs when some but not all of the epithelium is missing.
Fig. 9. Severe melting from excessive tear film enzyme activity.
the upper eyelid may be an early, yet subtle, sign of corneal ulceration. Fluorescein dye retention is diagnostic of a cor-
The Cornea is “Dry”
The cornea will appear dry if there is a deficiency of the precorneal tear film.
Corneal Ulcers Equine corneal ulceration is very common in horses and is a sight-threatening disease requiring early clinical diagnosis and appropriate medical and sur- gical therapy. Ulcers can range from simple superficial breaks or abrasions in the corneal epithelium (Figs. 10–12) to full-thickness corneal perforations with iris pro- lapse. Both bacterial and fungal keratitis in horses may present with a mild early clinical course, but require prompt therapy if serious ocular complica- tions are to be avoided. Many severe cases of equine ulcerative keratitis present initially as minor corneal epithelial ulcers or infiltrates with slight pain, blepharospasm, epi- phora, and photophobia. At first, anterior uveitis and corneal vascularization may not be clinically pronounced. Slight droopiness of the eyelashes of
neal ulcer. Faint fluorescein dye retention may in- dicate an abrasion or partial epithelial cell layer defect due to infiltration of fluorescein dye between inflamed epithelial cell junctions. Cobalt blue fil- ters can enhance detection of abrasions (Fig. 13). Fluorescein dye retention is bright in color when the entire corneal epithelium is missing to expose the stroma.
Corneal destruction results from the excessive production and release of proteinases and other en-
