A cataract occurs when the lens inside your rabbit's eye becomes cloudy or opaque. The lens is normally crystal clear and helps focus light on to the retina at the back of the eye. When a cataract develops, it blocks light from reaching the retina properly, which can affect your rabbit's vision. Cataracts can develop in one or both eyes and may progress at different rates.

Senile cataract in a 6-year-old rabbit with diabetes mellitus ©Vladimir Jekl

Light enters through the front of the eye and is focused by the clear lens onto the retina, which lies at the back of the eye. Information from the retina is transmitted to the brain, via the optic nerve, where processing of the image occurs. For the lens to work correctly, it must be perfectly clear to allow the light to pass through unhindered. When there is a cataract, the lens becomes opaque (like frosted glass) or even completely white. Light does not pass through it well in this state and vision is reduced to some degree. Severe cataracts can cause blindness.

Several factors can lead to cataract formation in rabbits. The most common cause is age-related changes, where the lens naturally becomes cloudy as your rabbit gets older. Some rabbits may inherit a tendency to develop cataracts from their parents. Other potential causes include eye injuries, infections, exposure to toxic substances, or complications from other health conditions like diabetes mellitus, although diabetes mellitus is extremely rare in rabbits. Poor nutrition, particularly vitamin deficiencies, may also contribute to cataract development. Encephalitozoon cuniculi is a protozoan parasite of the phylum Microsporidia closely related to fungi. The main host for this parasite is the domestic rabbit, but other mammals can also be affected including monkeys, foxes, birds, dogs, cats, mice and humans. A variety of clinical signs can be seen. Rabbits can be infected whilst in the womb (in vitro), due to the parasite invading the lens of the eye during pregnancy. This can rupture the lens material, releasing it into the anterior chamber (aqueous humor-filled space inside the eye between the iris and the cornea’s innermost surface) of the eye causing inflammation (phacoclastic uveitis). Usually this happens in one eye. Secondary increase in the eye pressure (glaucoma) and cataracts can also then occur.

The first thing you might notice is a whitish or cloudy appearance in your rabbit's eye. Your rabbit may seem more hesitant when moving around, especially in new environments or when light levels change. You might observe them bumping into objects they usually avoid or becoming startled more easily by sudden movements. If the rabbit has a companion, they may sit with them more than previously or move when the other rabbit does. Some rabbits may also show behavioral changes, becoming less active or more cautious during playtime. While these signs can indicate cataracts, only a veterinary examination can confirm the diagnosis. As a rabbit ages, the lens of the eye may take on a bluish or grayish color, which can be mistaken for a cataract. However, this is called nuclear sclerosis and is part of normal aging. Your veterinarian will be able to determine the difference between cataracts and nuclear sclerosis during an eye examination. Nuclear sclerosis does not affect the vision, and no specific treatment is needed.

Your veterinarian will perform a thorough eye examination using special equipment to look at the structures within your rabbit's eye. They will likely dilate your rabbit's pupils to get a better view of the lens and other internal eye structures. The veterinarian may also recommend additional tests to determine if there are underlying health conditions contributing to the cataract formation. They may advise bloods to look for the presence of an active E. cuniculi infection, especially in younger rabbits or if there are any other clinical signs. This complete examination helps determine the severity of the cataracts and the best treatment approach.

Treatment options depend on the severity and cause of the cataracts. In some cases, especially with early-stage cataracts, management might involve regular monitoring and supporting your rabbit's overall eye health. Surgical removal of cataracts is possible in rabbits, though it's more challenging than in other companion animals due to their unique eye anatomy. The surgery is performed by specialized veterinary ophthalmologists (eye specialists) and involves removing the cloudy lens and potentially replacing it with an artificial one. There are several different techniques, but the most common is called phacoemulsification, which uses ultrasound waves to break up the cataract. The lens fragments are then removed through a small incision in the eye. Following surgery, your rabbit will require eye drops for several months, which you will need to administer at home. If both eyes are affected, they can be done at the same time. As with all surgery in rabbits, there are anesthetic risks involved that you should discuss with your veterinary surgeon before making a decision on surgical removal of cataracts. Rabbits often adapt to some degree of sight loss or even blindness really well, and use their heighted sense of smell, hearing and touch to navigate around their environment, so surgery may not be the best option for your rabbit.

Creating a safe environment is crucial for rabbits with vision problems. Keep their living space consistent and avoid moving furniture or items in their habitat. Ensure food and water bowls remain in the same location. Remove ramps and any levels above the floor, which they may fall off of and injure themselves. Maintain regular feeding schedules and exercise routines to help your rabbit feel secure. Some rabbits may need help grooming areas they can't see well. Always approach your rabbit calmly and speak before touching them to avoid startling them. As with all rabbits, they should have a companion rabbit, who will offer support and company. This is particularly important for rabbits with sight impairment. If your rabbit does not have a companion, speak to your local rescue center about adopting a companion for them. Bonding of rabbits needs to be done carefully, especially if you have a rabbit whose sight is affected, so it is always advised to seek advice from individuals who have experience with bonding rabbits.

Contact your veterinarian immediately if you notice sudden changes in your rabbit's eye appearance or behavior. Warning signs include redness, discharge, squinting, excessive tearing, or if your rabbit starts rubbing their eyes frequently. Regular check-ups are important to monitor the progression of cataracts and adjust care plans as needed. Early intervention often leads to better outcomes, so don't delay seeking veterinary care if you have concerns about your rabbit's eye health.

Many rabbits with cataract adjust well to their changing vision, especially when changes occur gradually. With proper care and environmental modifications, rabbits can maintain a good quality of life even with reduced vision or blindness. If surgery is performed successfully, vision may be partially or fully restored. However, each case is unique, and your veterinarian can provide the most accurate prognosis based on your rabbit's specific situation.