A dog’s cornea is that part of the eye which is transparent. Since the delicate cornea is exposed to the elements, it is prone to being scratched, scraped and ulcer formation. To protect the sensitive cornea, it is bathed by a dog’s tears secreted from the tear ducts. Tears possess two major functions—that of lubrication and protection.
Scratches from playing around with other pugs are generally quite shallow and the cornea can heal rapidly. However, pugs can suffer from erosions of the cornea called ulcers. Corneal ulcers are often slow-healing and may be aggravated by infection with bacteria or fungi. When left untreated, these corneal ulcers can progress into complications that can threaten the loss of a dog’s eyesight.
Corneal ulcers may occur as a result of scratches, incessant pawing, or even bee stings. Bacterial infection can also cause the formation of on the surface of the eye. A scratch can tear the outermost layer of the cornea causing irritation and pain. A dog with a torn corneal covering often squints and tears are usually present.
A pug with a corneal ulcer may continually rub or paw at the affected eye thereby complicating the problem. There may be muco-purulent discharges that may accumulate in the dog’s eyes. If there is little damage and the ulcer is not as deep (also called a superficial corneal ulcer), healing may be fast and without severe complications.
The setting in of secondary bacterial infection may push the infection into the deeper layers of the cornea leading to the formation of deep ulcers. This type is called a deep corneal ulcer. Erosion of the cornea is often manifested by a bulge which is called a descemetocele. If left unchecked, the bulge can burst causing the collapse of the anterior part of the eye and spilling out of the contents of the eye leading to vision loss. It is for this reason that Pugs suffering from corneal ulcers should be carefully monitored by a veterinarian.
If the abrasions in the corneal surface are quite large, the entire cornea may become edematous. Once the cornea is filled with fluid, it turns white. Prompt treatment can aid in the rapid healing process of the cornea.
In superficial corneal ulcers, only the outer layer of the cornea is affected while a deep corneal ulcer involves almost half of the thickness of the cornea. In terms of healing, the healing period of superficial corneal ulcers is quite short while it may take several weeks or months for a deep corneal ulcer to heal. Although healing may take place, superficial ulcers often leave a scar in the cornea. Depending on the underlying causes, there are ulcers that may fail to heal even with treatment while there are those that heal and flare up again.
There are many ways to diagnose corneal ulcers. Your vet may recommend any of these diagnostic tests to come up with a correct diagnosis in order to commence with the right treatment regimen.
Shirmer Tear Test
The Shirmer Tear Test is a diagnostic tool that can measure the amount of tears present in the eye. This is an important test to establish whether an inadequate tear flow is the cause of the corneal ulcers.
The test uses Fluorescein dye strips to detect and reveal the presence of a tear or abrasion present on the corneal surface. The procedure involves putting a drop of topical anesthetic such as lidocaine on the surface of the affected eye. The dye strips are then moistened with saline and allowed to flow out over the cornea. To remove the excess dye on the eye’s surface, saline is used to gently wash it off. In the absence of tears or abrasions, no dye remains in the cornea and the eye remains clear however when there are broken corneal surfaces, the Fluorescein dye will stick to these raw areas and can be easily seen with the aid of a UV light and viewed through an opthalmoscope.
Aside from injury, corneal ulcers can also be predisposed by anatomical aberrations such as misplaced eyelashes, entropion (where eyelids curl inwards) or ectropion (outward curling of the eyelids). Certain breeds of dogs are susceptible to corneal ulcers because of their bulging eyes.