SYMPTOM
Cloudy or hazy eyes
Owners may notice a whitish, bluish, or milky appearance within one or both of their dog's eyes, sometimes developing gradually over weeks to months or appearing to change relatively quickly depending on the underlying cause.
Cataract
Cataracts produce opacity within the lens itself, creating a white or bluish-white cloudiness visible through the pupil. The cloudiness is located behind the iris and may affect part or all of the lens. Cataracts can develop due to hereditary factors, diabetes mellitus, age-related changes, trauma, or inflammation within the eye, and the rate of progression varies considerably depending on the underlying cause.
Nuclear sclerosis
Nuclear sclerosis is a normal age-related change in the lens that produces a symmetrical bluish-grey haze in both eyes, typically appearing in dogs over seven to eight years of age. Unlike cataracts, nuclear sclerosis does not significantly impair vision and the back of the eye remains visible through the lens on examination. This is one of the most commonly observed changes in ageing dogs and is frequently mistaken for cataracts.
Corneal disease
Conditions affecting the cornea, the clear front surface of the eye, can produce cloudiness that may be confused with lens opacity. Corneal oedema, corneal scarring, corneal dystrophy, and corneal ulceration can all cause haziness or whitening of the eye surface. Corneal cloudiness is located on the surface of the eye rather than deep within it and may be accompanied by redness, tearing, or squinting. A deep or softening ('melting') ulcer can progress to a hole through the cornea within about a day.
Uveitis (intraocular inflammation)
Inflammation within the eye can produce a hazy appearance due to inflammatory cells and protein accumulating in the aqueous humour, the fluid that fills the front chamber of the eye. This 'aqueous flare' creates a diffuse haziness rather than a discrete opacity within the lens. Uveitis may be caused by infection, immune-mediated conditions, trauma, or lens-related inflammation, and is often accompanied by redness, pain, and constriction of the pupil. Uveitis can itself go on to raise the pressure in the eye, and in many dogs it reflects disease elsewhere in the body.
Glaucoma
Elevated pressure within the eye can cause corneal oedema, producing a bluish-white haziness of the corneal surface. This cloudiness typically develops relatively quickly and may be accompanied by redness and signs of pain such as squinting. The corneal oedema in glaucoma reflects fluid accumulation within the corneal layers due to the elevated intraocular pressure. The pupil often looks wide and does not narrow in bright light. Raised pressure also damages the retina and optic nerve, and these cells do not regenerate. Loss of vision can begin within hours of a sharp rise and may be permanent within 24 to 48 hours. A visibly enlarged or bulging eye tends to develop only after the pressure has been high for some time, so a normal-sized eye does not rule glaucoma out.
Lens luxation (displaced lens)
The lens is held in place by fine fibres, and when these break down the lens can slip out of position. Primary lens luxation is an inherited condition linked in many breeds to a mutation in the ADAMTS17 gene. It typically appears between three and eight years of age, often in one eye first, with the second eye frequently affected later. Breeds covered by UK Kennel Club testing for it include several terriers, such as the Jack Russell and Parson Russell, as well as the Tibetan Terrier, the Lancashire Heeler and Chinese Crested. When the lens moves forward into the front chamber of the eye, it can block the drainage of fluid and raise the pressure quickly, with the same risk to vision as other forms of glaucoma. The eye may turn cloudy and red, and the dog may squint or hold the eye closed. A displaced lens is often not visible to an owner, and confirming it and measuring the pressure needs an eye examination.
Hyphaema (blood inside the eye)
Blood can collect in the front chamber of the eye. It may look like a red or dark haze, a small clot, or a red layer settled at the bottom of the chamber, and a mix of blood and inflammation can make the eye look cloudy rather than clearly red. Trauma is a common cause in dogs, though disease elsewhere in the body and disease within the eye itself are collectively more frequent. Other causes include uveitis, tumours inside the eye, retinal detachment, high blood pressure and problems with blood clotting, such as anticoagulant rodenticide poisoning or lungworm (Angiostrongylus vasorum) infection, which occurs in many parts of the UK. Where no injury is known, bleeding inside the eye can be the first visible sign of a clotting problem elsewhere in the body. The same process can cause bleeding into the chest, abdomen or joints that is not visible from outside, and none of this can be ruled out without blood tests. Blood in the eye can also lead on to raised pressure, cataract or adhesions within the eye.
Why timing matters
Early observation
A subtle haziness noticed in one or both eyes may initially be difficult to characterise without examination. In older dogs, nuclear sclerosis is the most common cause of a bluish lens haze and is a normal finding. Early cataracts may be noticed as a small area of whitish opacity visible under certain lighting conditions. Corneal changes may produce a more diffuse surface haziness that can develop over various timeframes depending on the cause. The context of onset, whether gradual or sudden, unilateral or bilateral, and the dog's age and health status, can help narrow the possibilities.
Later presentation
Cloudiness that becomes denser, spreads across more of the visible eye, or is accompanied by other changes such as redness, squinting, or apparent vision loss may indicate progression of the underlying condition. A cataract that transitions from partial to complete lens opacity can produce a noticeable change in the eye's appearance over a relatively short period. The development of redness, squinting or tearing alongside cloudiness changes the time frame. A corneal ulcer, uveitis, glaucoma and a displaced lens can all produce this picture, and they cannot be told apart reliably at home. Where the pressure is raised, loss of vision can become permanent within 24 to 48 hours rather than over weeks or months.
The trajectory of eye cloudiness depends heavily on its cause. Nuclear sclerosis progresses very slowly and symmetrically in both eyes over years. Hereditary cataracts may progress gradually over months to years, while diabetic cataracts can develop dramatically within days to weeks. Corneal conditions may follow variable courses depending on whether the underlying cause is addressed. A sudden increase in cloudiness, particularly when accompanied by pain, a pupil of a different size from the other or a change in eye size, may suggest a different process from the gradual changes seen with most lens conditions. In that setting the relevant time scale is hours rather than months, because pressure-related damage to the retina and optic nerve can begin within hours and a deep or softening ulcer can progress to a hole through the cornea within about a day.
Conditions commonly associated
Cataracts in Dogs
Cataracts produce opacity within the lens that creates visible cloudiness behind the pupil, ranging from a subtle haze in early stages to a dense white opacity in mature cataracts.
Corneal Ulcers
Corneal cloudiness develops around an ulcer as the normally transparent stroma absorbs water where the surface layer is lost, producing a visible white or blue-grey haze in the affected area.
The page on this condition is being checked again and is offline for now.
Glaucoma in Dogs
Corneal cloudiness in glaucoma results from oedema caused by elevated intraocular pressure forcing fluid into the corneal layers, producing a characteristic bluish-white haze.
Keratoconjunctivitis Sicca (Dry Eye)
Chronic keratoconjunctivitis sicca can lead to corneal changes including haziness, pigmentation, and neovascularisation, giving the eye a cloudy appearance.
Entropion
Chronic corneal irritation from entropion can cause corneal oedema, scarring, or pigmentation affecting clarity.
Uveitis
Inflammatory debris within the eye chambers causes visible cloudiness.
Nuclear Sclerosis
Bluish-grey haziness in the pupils is the characteristic visible sign of nuclear sclerosis.
Sensory Decline in Senior Pets
A bluish-grey haze to the lens, known as nuclear sclerosis, is a normal part of ageing eyes and often accompanies sensory decline.
Diabetic Cataracts
High blood sugar draws water into the lens and disrupts its fibres, turning the normally clear lens white or hazy, sometimes within days.
Hyperlipidaemia
A hazy or milky appearance to the front of the eye can develop when fat deposits accumulate within the cornea or the fluid of the eye.
Hyphaema
Blood pooling in front of the iris obscures the normally clear view into the eye, giving it a hazy or clouded appearance.
Lens Luxation
The eye can appear cloudy or hazy once the lens shifts out of its normal position and disrupts the clarity of the front of the eye.
The page on this condition is being checked again and is offline for now.
Pannus (Chronic Superficial Keratitis)
Pannus causes pigmented, vascular tissue to spread gradually across the cornea, giving the eye a persistent cloudy or hazy appearance.
When to explore further
A cloudiness that develops rapidly over days to weeks, particularly in a dog with known or suspected diabetes, may reflect a rapidly progressing cataract driven by osmotic changes within the lens.
When eye cloudiness is accompanied by redness of the white of the eye, squinting, tearing, rubbing at the eye, or a pupil that looks a different size from the other one, the picture differs from the painless haze of ageing. This combination can reflect a corneal ulcer, uveitis, glaucoma or a displaced lens. With raised pressure, damage to the retina and optic nerve can begin within hours, and vision in that eye can be lost permanently within 24 to 48 hours of a sharp rise. The pressure inside the eye cannot be judged by looking at the eye or touching it at home. It is measured with a tonometer, and that measurement is what separates glaucoma from uveitis, which can look very similar. How much vision is kept often depends on how many hours the pressure stays high, so even a single night of watching a painful cloudy eye can cost the vision in that eye.
Cloudiness affecting only one eye may have different significance from symmetrical bilateral changes, as unilateral processes are more likely to reflect local pathology such as trauma, focal inflammation, or a lens-specific abnormality rather than the systemic or age-related processes that typically affect both eyes.
A dog with cloudy eyes that also shows signs of vision impairment, such as bumping into objects, hesitating at stairs, or showing reduced confidence in unfamiliar environments, may have progressed beyond the point where the cloudiness is incidental.
In breeds known to be predisposed to hereditary cataracts, lens cloudiness appearing at a young age is more likely to be an inherited cataract than an age-related change, and its type and likely course can only be characterised by an eye examination.
A red or dark haze inside the eye with no known injury can be the first visible sign of a clotting problem, such as anticoagulant rodenticide poisoning or lungworm. Bleeding from a clotting problem can also be happening inside the chest or abdomen, where it is not visible, and can become life-threatening.
Observing whether the cloudiness appears to be on the surface of the eye or deeper within it, whether it is present in one or both eyes, and whether it has changed over time can help build an initial picture. Noting whether the dog's behaviour suggests any visual difficulty, such as changes in confidence navigating, catching ability, or responsiveness to visual cues, provides complementary information. Understanding that a bluish haze in an older dog's eyes is most commonly a normal age-related change can help calibrate the level of concern. That reassurance applies to a comfortable eye with a similar haze on both sides. A cloudy eye that is also red, squinting, watering or has a pupil of a different size from the other follows a different pattern, and its cause cannot be worked out by observation at home.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS