You have noticed that your four-legged friends’ eyes appear bluish-grey or hazy and you didn’t notice it before.  What are the causes, and should you be worried?Cloudy eyes are a symptom of a variety of eye conditions.  Knowing the difference between these will alleviate your concerns, and help you decide whether to seek veterinary advice.

The most common causes of cloudy eyes are nuclear sclerosis and cataracts.

Nuclear sclerosis (Lenticular sclerosis) is when the lens nucleus becomes denser and harder and will be visible as a greyish blue haze.  It rarely causes vision impairment but focusing ability may be affected. This condition is usually gradual, and age related from 6 years.  Advanced nuclear sclerosis may appear like a cataract and is frequently confused by owners.

Cataracts is the loss of transparency of the lens nucleus as a result of abnormal lens metabolism and will appear white or opaque.  Cataracts usually come on suddenly, but it can be an inherited trait and will then develop gradually, so don’t assume slow change equals sclerosis.  Cataracts can cause vision impairment, glaucoma, pain and blindness if not treated.   Common causes for cataracts include: Inherited conditions, Diabetes, Ocular disease, Physical trauma, Nutritional deficiency, Aging (over 8 years).

Less common causes of cloudy eyes, but of greater concern are glaucoma, nuclear dystrophy, pannus, corneal ulcers, dry eye and anterior uveitis.

Diagnosing and Treating Cloudy Eyes in Dogs

Treatment for your dog’s cloudy eyes depends on the cause, the age of your dog, the progress of the problem, and your dog’s discomfort.

Watch your dog closely for other symptoms of eye problems, such as increased discharge, squinting, or a change in your dog’s eyes shape, size, colour, or vision, and contact your veterinarian as soon as possible if you notice redness, squinting, or thick discharge from your dog’s eye, in addition to cloudiness.


What is a cataract?

A cataract is an opacity of the lens. This opacification results in less light reaching the nerve layer of the eye known as the retina. This, in turn, can lead to reduced vision and ultimately blindness. A cataract may start as a small opacity that gradually enlarges. It is very difficult to predict the rate of progression, but most cataracts will mature and lead to blindness.

Causes of cataracts

Many conditions have been known to cause cataracts. These include:

  • Hereditary (genetic) predisposition
  • Severe inflammation in the eye
  • Blunt trauma to the eye or a perforating foreign body that can strike the lens
  • Radiation (for example following radiation therapy to tumours near the eye)
  • Electrocution following a pet biting an electrical cable
  • Secondary to ageing
  • Diabetes mellitus
  • Retinal disease (for example progressive retinal atrophy)

Is my pet a good candidate for cataract surgery?

Cataract surgery is an elective procedure. As such, it is important to ascertain that your pet is healthy and that there are no underlying conditions that may affect the outcome of the surgery.  It will be recommended that certain pre-operative blood tests are undertaken to ensure that your pet is a suitable candidate for surgery.

Because the retina can not be visualized through an opaque lens, another diagnostic modality to ensure normal retinal function before the surgery. This modality is electroretinography – a test performed under topical anaesthesia and sedation if necessary. Using a computer, the electrical response in the eye is measured following its stimulation with light.  Cataract surgery will only be done if your pet has normal retinal function.

After the electroretinogram an ultrasound examination of the eyes have to be performed to allow one to see behind the opaque lens and ensure that there is no small retinal detachment and that the vitreous, (the jelly behind the lens) is normal.


A cataract can only be removed surgically, and not by medications. Techniques in man and animals have progressively improved over time and the current method for cataract removal is by a process called phacoemulsification. This is not laser treatment. In animals this surgery is done under a general anaesthetic.

Will the cataract grow back?

Some patients may have remnants of lens fibres re-growing and forming a scar on the remaining back capsule of the lens that can interfere with the visual axis and cause reduced vision. This is not a common complication and the incidence is much reduced by implanting an artificial lens. However, if it occurs it can be treated by entering the eye a second time to remove the opaque capsule. In some cases, this capsule can be removed by laser, which means it is not necessary to open the eye a second time. This phenomenon is not uncommon in man following surgery and usually is corrected by a subsequent laser surgery.


Glaucoma is an increase of the pressure inside the eye. Fluid is constantly being produced in the eye. This fluid then flows through the pupil and drains out of the eye through the angle between the cornea and the iris. If there is decreased drainage, the pressure in the eye increases, leading to damage to the retina and optic nerve. If untreated this will lead to permanent blindness.


There are several causes but we generally classify glaucoma as primary and secondary. Primary glaucoma is an inborn defect of the drainage angle and is breed predisposed in a number of breeds, for example Siberian Huskies, Flat Coated retrievers and Bouviers.

Secondary glaucoma is caused by a mechanical obstruction to the drainage of fluid. This can be caused by a number of causes which include inflammation and its sequelae, intra ocular tumours, luxation of the lens and bleeding within the eye.

Diagnosis and treatment

Special instruments are needed to measure the pressure in the eye. It is very important to determine the cause of the glaucoma and this should be treated. We also use drugs to decrease the production of fluid. In certain cases the condition has to be treated surgically in order to restore adequate drainage from the eye.