South Texas Veterinary Ophthalmology
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Diseases of the Cornea
The cornea can be considered the window to the eye. The cornea is a highly transparent and complex structure. The typical canine corneal thickness is ½ millimeter. The cornea is composed of multiple layers including the epithelium (most superficial), the stroma (middle layer and comprises most of the corneal thickness), and the endothelium (mot inner layer). Changes or damage to the cornea may not only result in loss of vision, but is a potentially painful condition.
The most common problems of the cornea include:
What is a corneal ulcer?
By definition, corneal ulcers are disruptions of the different layers of the cornea. Ulcers can range from superficial (disruption of the superficial epithelium only), deep (loss of portions of the corneal stroma), to perforating (full thickness defect).
What are the signs of a corneal ulcer?
The cornea is one of the most innervated parts of the body. Thus, damage to the cornea is very painful. Signs of ocular pain include squinting, rubbing, and avoidance of light (photophobia). Other symptoms associated with corneal ulcers include redness, cloudiness, and ocular discharge.
What causes a corneal ulcer?
The most common cause of corneal ulcers are trauma. Other causes include eyelid abnormalities such as improper eyelash growth (distichia) or placement (ectopic cilia) and enrolling of the eyelid (entropion); decreased tear production (keratoconjunctivitis sicca); inability to blink properly (lagophthalmos); and loss of corneal innervation (neutrogenic keratitis).
What is the treatment for a corneal ulcer?
The treatment for uncomplicated superficial corneal ulcers is strictly medical, mostly antibiotic drops to prevent secondary infection and a topical analgesic to relieve the pain. A superficial ulcer should heal within a week. Superficial ulcers that fail to heal within a week or eyes that get recurrent ulcers indicate that there is an underlying problem (such a lid problems or keratoconjunctivitis sicca). Identification of the complicating condition and proper treatment to resolve the problem is necessary to allow for successful resolution of the ulcer.
Deep corneal ulcers (ulcers extending more than half the corneal thickness) require surgical management as well as medical therapy for a successful outcome. Surgical treatment of deep corneal ulcers have a high success rate (>90%) resulting in a comfortable and visual eye.
An ulcer that is allowed to continue to full thickness causes a corneal perforation or a breach of the globe. Correction of this problem is possible and vision can potentially be restored, but requires significant surgical and medical management.
What is a corneal laceration?
A corneal laceration is the sharp disruption of the cornea. Corneal lacerations vary in depth from partial thickness to full thickness lacerations. Corneal lacerations are always associated of a sharp trauma.
What causes a corneal laceration?
Corneal lacerations are always a result of a sharp trauma of the eye, and can be potentially coupled with a lens laceration. Cat scratches to the eye are the most common presentations.
Why are corneal lacerations important?
Disruption of the cornea results in the loss of structural integrity of the globe as well as being very painful. A corneal laceration that is not treated properly can result is permanent damage to the eye that may result in decreased vision or even loss of the eye.
What is the treatment for a corneal laceration?
The treatment for a corneal laceration is the surgical repair of the cornea. If the globe has been ruptured, certain substances are needed to reform the globe. If the lens is also lacerated, removal of the lens, in a process known as phacoemulsification, will need to be performed. This advanced procedure allows for the complete removal of the lens and, if the lens capsule is sufficiently intact, placement of an artificial lens that will result in the return of normal vision. A corneal laceration is considered an emergency and should be addressed immediately.
