Why Do Cats Have Cross-Eyes? Does Strabismus Affect Their Vision? A Deep Dive into the Causes, Effects, and Treatment of Strabismus in Cats

Why Do Cats Have Cross-Eyes? Does Strabismus Affect Their Vision? A Deep Dive into the Causes, Effects, and Treatment of Strabismus in Cats

Have you ever seen a cat with crossed eyes? They may look adorable and goofy, but it’s natural to worry about their vision. Strabismus, also known as cross-eyes or squinting, is not uncommon among cats. So, what causes feline strabismus? And does it affect their vision and daily life?

What Causes Strabismus in Cats?

The muscles that control the movement of a cat's eyeballs are connected. If these muscles become abnormal, or if the nerves that control them or the brain are damaged, the eyeballs will move in an abnormal direction, causing strabismus. Cross-eyes is a case of inward strabismus.

For cats, most cases of strabismus are caused by genetics (congenital defects in the eye muscles or brain development). This typically does not cause any further harm to the cat’s overall health and can be observed from birth.

However, if a cat develops strabismus later in life, it is most likely caused by an underlying medical condition, such as:

Vestibular system disease (inner ear disease): The vestibular system is responsible for balance and spatial orientation. If it malfunctions, the cat may experience strabismus, head tilt, unsteadiness, and other symptoms.
Eye trauma: Eye injuries, such as being poked by sharp objects or scratched by other animals, can lead to strabismus.
Feline leukemia: Feline leukemia can weaken a cat's immune system, making them more susceptible to other illnesses, including eye diseases that can cause strabismus.
Nerve damage: Nerve damage, such as a concussion or spinal cord injury, can lead to strabismus.
Hydrocephalus: Hydrocephalus causes an increase in cerebrospinal fluid pressure, which can put pressure on the eye muscles, resulting in strabismus.
Brain or nervous system cancer: Tumors growing in the brain or nervous system can put pressure on the eye muscles or nerves, causing strabismus.
Benign or malignant tumors (growing pressure): Tumors in the eye or brain can grow and put pressure on the eye muscles or nerves, also causing strabismus.

Does Strabismus Affect a Cat's Vision?

Cats with congenital strabismus usually adapt quickly.

A study conducted at the University of California in 1980 found that cats who developed strabismus at 4-5 months old could adapt within weeks to months through self-regulation (eating, playing, and jumping accurately). Researchers designed a device to assess a cat’s ability to judge the position of an object relative to its own position (egocentric localization) by observing where the cat landed when jumping onto a platform.

Normal cats landed in the center of the platform, while cats with early strabismus landed off-center.

4-month-old cats with strabismus landed off-center initially, but after a few weeks of practice, they were able to land in the center. This suggests that young cats with strabismus can adapt quickly to this change. Several 5-month-old cats who had lived with strabismus for some time landed in the center on their first jump. This indicates that they self-regulated without any intervention.

However, when cats develop strabismus after 9 months of age, their ability to adapt through self-regulation is significantly reduced.

They have different ways of adapting.

Humans with strabismus who do not wear glasses or undergo corrective treatment may get used to using their normal (non-strabismic) eye to see the world (this can also lead to using only one eye, making strabismus potentially worse). What happens to cats with strabismus? How do they assess their own position and the position of objects?

Research shows that cats adapt in various ways:

First, some cats, like humans, prefer to use their normal eye, while others use their strabismic eye.
A: Normal or cats using the normal eye observe the platform with a "straight head" before jumping.
B: Cats with strabismus use both eyes or the strabismic eye and tilt their head to observe the platform.

Second, some cats use "their brains" to correct their behavior. "If I always jump toward the middle and end up on the left, then I'll jump towards the right next time, and eventually, I'll land in the middle." Some cats with strabismus have been observed using this method to accurately land in the center after a few weeks.

The entire experimental process is complex, involving putting "glasses" on the cats to cover either the left or right eye. If you're interested, you can look at the specific experiment in reference 2.

While it may seem like congenital or early-onset strabismus has a minimal impact on a cat’s life, there are still risks:

Amblyopia and vision loss: Several experiments conducted between 1980 and 1984 revealed that cats with strabismus, like humans, often develop amblyopia (lazy eye) in the strabismic eye. Among 4- to 5-year-old cats with strabismus, many exhibited amblyopia in the strabismic eye. Some older cats who developed strabismus later in life even developed amblyopia in both eyes, resulting in significant vision loss, reluctance to move, and noticeable mood swings.

Therefore, especially for cats with strabismus caused by an underlying medical condition, it is crucial to pay attention to their strabismus, both for treating the primary illness and for protecting their vision and ensuring their quality of life.

Can Strabismus Be Diagnosed and Treated?

Possible diagnostic tests:

History taking: A complete medical history helps with diagnosis.
Physical examination and neurological and ophthalmological evaluations: Helps distinguish between problems in the eyes, muscles, nerves, or brain.
Complete blood count and biochemistry: Detects malignant tumors.
Urine analysis: Rules out potential bacterial infections.
CT or MRI: Scans the brain and eyes.

Ophthalmological examinations also include tear test strips, pupillary light reflex, intraocular pressure, and fluorescein staining.

Treatment principles:

Congenital strabismus caused by genetics typically does not affect a cat’s daily activities or quality of life and usually does not require treatment. However, strabismus caused by other factors later in life should be addressed.
If strabismus is caused by eye muscle problems, it can be corrected through surgery, but if it does not impact quality of life, surgery is generally not recommended (requires general anesthesia).
For tumors, radiation therapy, chemotherapy, or enucleation (eye removal) may be necessary.
If bacterial infections affect the vestibular system, antibiotics may be used.

What Are the Care Considerations?

Ideal eye exercises:

Theoretically, post-surgery or cats unsuitable for surgery can undergo physical therapy, similar to human strabismus correction, through eye exercises to strengthen eye muscles. This involves closing the normal eye and using the strabismic eye to look up, down, left, and right to exercise the strabismic eye muscles; gently pressing and massaging the strabismic eye muscles. However, most cats don’t cooperate.

How to ensure a cat’s quality of life:

Cats with congenital strabismus who have no overall vision impairment can be cared for normally. For cats with acquired strabismus, even if their vision in one eye is unaffected, they may experience double vision and blurry vision (seeing double), so it's recommended:

Avoid moving furniture and cat supplies as much as possible.
Use steps, cushions, and chairs to minimize the height difference between beds, sofas, and windowsills where the cat might go.
Use interactive toys that make noises (balls with rattles, cat wands that make rustling sounds and whistles when waved) instead of silent toys.

Takeaways:

While crossed eyes in cats can seem cute, there might be underlying health issues. Observing changes in your cat’s behavior and taking them to a veterinary professional for diagnosis and treatment can help them live a better life.

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