Introduction

Cat Eye Syndrome, or CES for short, is a rare genetic condition that affects approximately 1 in 50,000 to 1 in 150,000 live births.^1,2 Despite its name, cat eye syndrome doesn't just affect the eyes. It can impact various parts of your child's body, including the ears, heart, and kidneys, by interfering with the developmental process and affecting their functions.

One of the important aspects of CES is its effect on hearing and ear structure. Many children with CES may experience hearing loss, which in many cases can lead to developmental delays and intellectual disabilities, especially if not diagnosed and managed early. That's why understanding the link between CES and hearing problems is important for timely intervention.

In this article, you’ll learn about:

• What is Cat Eye Syndrome 
• How it can affect your child’s ears and hearing
• The types of hearing loss seen in CES
• How is hearing loss detected
• Treatment and support options for children with hearing loss

What is cat eye syndrome?

Cat eye syndrome, also known as Schmid Fraccaro syndrome, occurs when there is an abnormality in the 22nd chromosome, which can interfere with the normal development of your child. Normally, people have 46 chromosomes arranged in 23 pairs. In CES, your child has an extra piece of chromosome 22, which means that it may be present three or even four times instead of the usual two.^1,2,3

This condition can affect different parts of the body, leading to a wide range of symptoms. One of its characteristic features is iris coloboma, a defect in the lower part of the iris (the coloured part of the eye). The iris may not have been formed properly, or may have a gap in its lower portion, giving the eyes an appearance similar to that of a cat. This characteristic appearance is what gives the syndrome its name.³ However, not all children with CES have this feature.

Other problems that may be associated with CES include ear problems (discussed below in detail), congenital heart defects, kidney problems, and anal atresia (a condition where the opening of the anus may be missing or blocked).^1,2 However, each person with CES has a unique set of symptoms, which makes it difficult to diagnose. Reports show that only 41% of people with this condition have the classical features, which include iris coloboma, preauricular skin tags or pits, and anal atresia.^1,4  

Now, let's take a closer look at how CES affects the ears. To learn more about its impact on other body parts, click here.

Common ear anomalies in cat eye syndrome

Many children with CES are born with noticeable differences in the shape, size, or position of their ears. These are called ear anomalies, and they are often among the earliest physical signs that doctors may observe. While these differences may vary from one child to another, some of the most common ear differences include:³

Preauricular skin tags or pits

These are the most frequently observed ear anomalies in CES.² Preauricular skin tags are small, harmless outgrowths of skin, which appear as elevations or bumps, while pits are small depressions in front of the ears (preauricular).

Abnormal structure of the ears

You may notice that your child has unusually shaped or low-set ears, meaning that they are located lower on the head than usual. The auricle (the external part of the ear) may be smaller or malformed, a condition known as microtia. In some children, the earlobes (soft lower part of the external ear) may be underdeveloped (known as hypoplastic earlobes), and the antihelices (the curved outer edges of the ear) might appear more prominent than usual. 

Abnormalities of the ear canals

In some cases, the ear canals may not form properly. They may be unusually narrow (stenosis) or even absent, a condition known as auditory canal atresia. These structural issues can significantly affect hearing and may require specialized evaluation and treatment.

All these anomalies occur during early pregnancy when the baby's ears are being formed. Even though these might not always result in hearing issues, they usually indicate that a closer look at the ears is necessary, especially for children who have been diagnosed with CES.

Hearing loss in cat eye syndrome

Before learning about hearing loss, it may be helpful to know how the hearing process actually works. Your ear consists of three parts: the external, middle, and inner ear. Sound travels through the external ear and reaches the eardrum, causing it to vibrate. From there, these vibrations travel through the small bones in the middle ear to the inner ear (cochlea), where they're converted into electrical signals. These signals then travel along the auditory nerve to the brain, which interprets them as sound.

In children with cat eye syndrome (CES), hearing problems may occur and vary in severity from one child to another. However, it is possible that your child has normal hearing at birth but may develop hearing loss later in life. Three main types of hearing loss might arise in CES, depending on how the ears are affected.

• Conductive hearing loss: The most common type is conductive hearing loss, which happens when sound can’t travel properly through the outer or middle ear.⁵ This is often due to structural differences, such as small or missing ear canals or abnormal middle ear bones. In some children, repeated ear infections can also cause temporary hearing problems
• Sensorineural hearing loss: This happens when there is damage to the inner ear or the auditory nerve that connects the ear to the brain. It may result from abnormal development of the inner ear structures due to the genetic changes seen in CES
• Mixed Hearing Loss: Some children may experience both conductive and sensorineural hearing loss at the same time

Since hearing is essential for speech and learning, early testing and treatment are very important. Identifying the type of hearing loss early can help children receive the right support for speech development and communication skills.

How hearing problems are detected

CES is usually diagnosed right after birth, based on visible physical signs such as unusual ear shapes, preauricular skin tags or pits, or other noticeable differences. However, to confirm the diagnosis, doctors usually perform a blood test such as a karyotype or chromosomal microarray, which checks for extra genetic material on chromosome 22.^4,5

Because children with CES have a higher risk of developing hearing loss, it is very important to screen for hearing problems early, even if the baby appears to hear normally. Identifying hearing issues at an early stage can help support better speech, language, and cognitive development.

At birth, most hospitals perform newborn hearing screening tests to check for any issues. These may include:

• Auditory Brainstem Response (ABR): This test evaluates how well sound signals travel from the inner ear to the brain
• Otoacoustic Emissions (OAE): This test checks whether the inner ear (cochlea) is functioning properly

However, a normal result doesn’t always guarantee perfect hearing, especially in conditions like CES. That is why follow-up tests are recommended as the child grows.

Common tests include:

• Tympanometry: This test assesses how well your middle ear is working and how your eardrum moves
• Tuning fork tests: These tests detect the presence  and type of hearing loss
• Audiometry tests: These tests check which type of hearing loss they have and if it is mild, moderate, or severe

Treatment options

Since CES is an inherited condition, there is no cure available for it, and the treatment focuses on managing the symptoms. As CES can affect multiple systems of the body, children are usually cared for by a team of specialists, which may include eye, ENT, heart, and child specialists.⁵ For hearing loss, doctors usually recommend different treatments depending on their type and severity.⁶ The most commonly used are:

Conductive hearing loss

For conductive hearing loss, medications such as antibiotics (for infections) or antihistamines (for allergies) are usually given first.⁶ If these do not work, surgical procedures such as myringotomy and tympanoplasty are usually performed. 

Sensorineural hearing loss

For sensorineural hearing loss, hearing aids are often recommended. These are small electronic devices that amplify the sound to make it easier for your child to hear. They are of different types. In cases of severe hearing loss, a cochlear implant may be considered. This is a surgical procedure in which a device is placed in the inner ear that directly stimulates the auditory nerve. This, in turn, sends signals to your brain that are interpreted as sound.

Developmental support

Managing hearing loss is not just about treating the ears, it is also about supporting your child's overall development, communication, and learning. Working with speech-language therapists and early intervention specialists can help your child build strong communication abilities, even if their hearing is limited. Some children may benefit from sign language, visual learning tools, or special education services tailored to their needs. Starting support as early as possible can make a big difference in how well your child learns to interact and express themselves.

Summary

Cat Eye Syndrome (CES) is a rare genetic condition that can impact your child’s eyes, ears, heart, kidneys, and more. Many children with CES are born with unusual ear shapes or skin tags near their ears, and some may also experience hearing loss. This hearing loss can either be present at birth or develop later on, affecting speech, learning, and social growth. That is why early hearing tests and follow-ups are important for a timely diagnosis. Depending on the type of hearing loss your child has, treatment options might include medications, surgery, hearing aids, or cochlear implants. In addition to that, developmental support like speech therapy and special education can greatly improve your child's learning and communication abilities. By understanding the signs and knowing the available support for CES, you can help ensure better outcomes and a richer quality of life.