Unless your pet has natural baby blues, you shouldn’t see a blue, gray, or cloudy cast to their eyes. This color change can indicate normal aging, or may be a clue to an underlying eye disease. The color change can originate from inside the eye or appear on the eye’s surface. The Veterinary Vision Center team can examine your pet to distinguish between the different blue eye causes and develop the best possible treatment plan. Here are the most common diseases that result in a cloudy or blue eye.
#1: Pet nuclear sclerosis
The eye’s lens sits behind the iris and pupil, and helps focus light on the retina for crisp vision. The visible lens portion can be seen through a pet’s pupil, appears clear, and works to improve their near vision and depth perception. Over time, all pets will develop nuclear sclerosis to some degree—this is the same condition that causes people over 40 to need reading glasses.
Nuclear sclerosis causes the lens to stiffen so it cannot focus light as well, leading to minimal functional vision change for most pets, although some have more difficulty than others. The lens stiffening also results in mild lens clouding, which can appear hazy or blue in certain lights, although pets can easily see through this cloudy change.
#2: Pet cataracts
Cataracts are different from nuclear sclerosis. They cause an opaque white color to appear on the lens that may be present focally or throughout the entire lens. While cataracts commonly form with age, they also can occur in younger pets, and may result from genetic, inherited, or nutritional factors, or from systemic disease. Cataracts are common in dogs, especially in those with diabetes, but uncommon in cats.
This eye condition will progress over time and may result in complete blindness, although many pets are candidates for cataract removal surgery to restore vision. For pets who cannot undergo surgery, a cataractous eye is treated with anti-inflammatory eye drops to prevent long-term complications from inflammation, which may include lens luxation, glaucoma, or retinal detachment.
#3: Pet corneal degeneration or dystrophy
The cornea is the clear window that covers the iris and pupil and serves to protect the eye’s interior, as well as focus light for vision. When the cornea is damaged by disease or age, it becomes less efficient at maintaining the delicate water balance that provides its clear structure. This water buildup (i.e., corneal edema) appears cloudy and bluish, and also can make the eye look larger.
A common cause of corneal fluid buildup is corneal endothelial dystrophy, in which the deepest corneal cell layer degenerates and allows too much fluid inside. This condition occurs in middle to older age, is most common in Boston terriers, Chihuahuas, and dachshunds, and can progress to complete blindness. Corneal dystrophy is painless, but can lead to blisters (i.e., bullae) that may rupture and leave a corneal ulcer, which can cause discomfort or infection. Treatment includes a high-concentration sodium eye ointment to help prevent bulla formation, but that will not slow or stop vision loss. A similar condition, corneal degeneration, leads to fluid, fat, or mineral buildup in the cornea.
#4: Pet glaucoma
Glaucoma results in high eye pressure that often leads to blindness. Glaucoma also may cause corneal edema, which occurs as the high eye pressure pushes fluid from inside the eye into the cornea. In contrast to endothelial dystrophy, glaucoma results in significant pain and discomfort, and requires immediate treatment to preserve a pet’s vision as long as possible. Treatments may include eye drops, medications, outpatient procedures, or surgeries to save their vision or to promote comfort in a permanently blind eye. Any pet displaying the blue color change indicative of corneal edema needs prompt evaluation to rule out glaucoma.
#5: Pet anterior uveitis
The anterior uvea includes the iris and front eye portion that contains a fluid called aqueous humor. In uveitis these eye structures become inflamed, which causes the eye’s fluid or cornea to appear cloudy. Severe uveitis can cause tissues to stick together (i.e., synechia), blocking fluid drainage and leading to secondary glaucoma. Most pets with uveitis have a cloudy, red, painful eye.
Uveitis sometimes is caused by serious systemic disease, such as fungal infection, cancer, tick-borne infections, or viral diseases. Blood, urine, and imaging tests can help rule out these conditions and find the correct treatment for your pet.
#6: Pet corneal ulcers
Corneal ulcers are scratches or abrasions on the eye surface that disrupt the cornea’s outer layer. Without the outer protective cell layer, the normal tear film can seep into the cornea and cause a focal fluid buildup around the ulcer. If you notice a cloudy spot on your pet’s eye and they also are squinting or showing other signs of discomfort, check with your veterinarian to rule out a corneal ulcer. Treatment usually includes antibiotic drops, but also may require minor procedures or major surgeries for long-standing or severe ulcers.
An eye color change without vision issues or signs of discomfort should be checked out by your primary veterinarian or the Veterinary Vision Center team. If you notice an eye color change in your pet, along with vision changes, redness, squinting, pawing, or excessive tearing, contact us or visit your local veterinary emergency facility for urgent care and evaluation.
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