The cornea is the transparent cover over the front of the eye. When inflamed, it swells with fluid (edema), and becomes cloudy.
• Corneal edema may appear as a hazy, blue, or milky opacity covering the surface of the colored part of the eye
• Any irritant, injury, or other ocular condition may lead to corneal edema
• Upper respiratory tract infections caused by feline herpesvirus are one of the most common causes of corneal edema
• While not life threatening, prompt veterinary intervention is required to have the best chance of retaining vision
• Diagnostics include ophthalmic examination and blood tests
• Treatment and prognosis vary depending on the underlying condition, and often include both topical and systemic medication and surgery
Corneal edema is associated with a variety of eye conditions in cats. It is often associated with eye injuries and degenerative ocular diseases. Corneal edema does not always develop immediately following an injury. It can take hours or days for swelling in the cornea to appear, and result in opacification of the cornea.
Herpes viral infections usually show other symptoms of an upper respiratory tract infection, such as sneezing, nasal discharge, and appetite loss.
A healthy cornea is normally clear, but when it becomes injured or inflamed it swells, retaining serum and growing blood vessels to provide nutrients needed for healing. These fluids are opaque, and create a hazy, cloudy appearance to the eye.
Injuries and herpesvirus infection are two of the most common causes of corneal edema.
Corneal inflammation can also occur from a variety of specific ocular conditions, including:
• Ulcerative keratitis (a corneal ulcer)
• KCS (keratoconjunctivitis sicca, “dry eye”)
• Eyelid and eyelash disorders
• Cancer of the eye
• Excessive UV exposure
Cats commonly experience corneal edema because it is associated with so many different ocular conditions. The associated conditions can cause significant discomfort, and potentially lead to loss of vision. Immediate veterinary intervention is required to have the best chance of avoiding complications.
Diagnostics include physical examination and ophthalmic examination. An ophthalmic examination consists of several tests, including using fluorescein dye to evaluate the integrity of the cornea, microscopic examination of the corneal tissue, tonometry (measuring eye pressure), and Schirmer tear test.
Additional diagnostic tests include:
• Microscopic examination of cells from the cornea
• Culture from the cornea and conjunctiva
• FeLV/FIV testing
Treatment varies depending on the underlying cause, and often includes
• Surgery, including ocular grafts
The ‘cloudy’ eye associated with corneal edema affects the outer surface of the eye. Conditions which affect inner structures of the eye, such as the lens or pupil, may be mistaken for a corneal edema, as they can have a similar opaque coloration. This is especially true if the lens of the eye moves out of its normal position, as in cases of cataracts, lenticular sclerosis, or anterior lens luxation.
Conditions which cause a buildup of pink tissue over the front of the eye (almost looking like skin) can also be confused for a corneal edema, as in conditions of pannus or conjunctival tumors.
• Nasal discharge
• Elevated third eyelids
• Runny eyes (epiphora)
• Mucus discharge from the eyes
• Pink or red color to the cloudy surface of the eye
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