Keratoconus

What is keratoconus?

Keratoconus is a progressive eye condition in which the cornea — the clear, dome-shaped front window of the eye — gradually becomes thinner and begins to bulge outward into a cone-like shape. A healthy cornea is smooth and evenly curved, which allows it to focus light sharply onto the retina at the back of the eye. When the cornea thins and steepens irregularly, light rays are scattered rather than focused cleanly, and vision becomes blurred and distorted. Understanding what is keratoconus and how it develops helps patients recognize the condition early, when treatment can be most effective at preserving vision.

Keratoconus most often begins during puberty or the late teenage years and may continue to progress into a person’s twenties or thirties. In many people, the condition slows or stabilizes with age, although this cannot be guaranteed for any individual. Both eyes are usually affected, though often one eye is worse than the other, and the two eyes may progress at different rates. Keratoconus affects people of all backgrounds and both sexes, and while it is not one of the most common eye diseases, it is one of the more frequent reasons for corneal transplantation in younger adults when advanced disease develops.

The condition is classified under the ICD-10 code H18.609 (keratoconus, unspecified). Keratoconus is not an infection and is not contagious. It is generally considered a structural weakness of the corneal tissue, in which the collagen fibers that give the cornea its strength and shape become less able to hold the normal dome-like curvature.

Symptoms of keratoconus

Keratoconus symptoms tend to develop slowly and can be subtle at first. Many people initially believe they simply need a new eyeglass prescription, because the earliest sign is often a change in vision that keeps shifting. Common keratoconus symptoms include:

• Blurred or distorted vision that is not fully corrected by standard eyeglasses
• Frequent changes in eyeglass or contact lens prescriptions, often over a short period
• Increased sensitivity to light (photophobia) and glare, especially at night
• Halos or streaks around lights, particularly when driving after dark
• Ghosting or multiple images seen with one eye (monocular double vision)
• Eye strain, headaches, or difficulty reading caused by the effort of focusing
• Worsening night vision
• Sudden clouding of vision with pain and redness in rare, advanced cases (a complication called corneal hydrops, explained below)

Symptoms usually differ by stage. In early keratoconus, the main complaint is mild blurring and increasing astigmatism — an irregular curvature of the eye that distorts vision — which glasses can often still correct. In moderate disease, the distortion becomes more irregular, glasses become less effective, and specialized contact lenses may be needed to see clearly. In advanced keratoconus, the cornea may become significantly thinned, steepened, and sometimes scarred, and vision may be poor even with contact lenses.

A rare but important event in advanced disease is acute corneal hydrops. This occurs when the innermost layer of the stretched cornea develops a break, allowing fluid from inside the eye to enter the corneal tissue. The cornea suddenly becomes swollen and cloudy, and the eye may become painful, red, and very sensitive to light. Hydrops usually settles over weeks to months but can leave scarring, and it requires prompt medical attention.

Because both eyes can be affected unevenly, some people compensate with their better eye for a long time and only notice a problem when the stronger eye also begins to change. This is one reason routine eye examinations are valuable, especially for teenagers and young adults whose prescriptions change frequently.

Causes and risk factors

The exact keratoconus causes are not fully understood. Most researchers believe the condition results from a combination of genetic predisposition and environmental influences that weaken the structure of the cornea. In affected corneas, the collagen fibers and the supporting tissue between them appear less organized and less resistant to the normal pressure inside the eye, allowing the cornea to gradually thin and bulge.

Recognized risk factors and associations include:

• Family history. Keratoconus can run in families. Having a parent or sibling with the condition increases the likelihood of developing it, although many patients have no affected relatives.
• Chronic eye rubbing. Vigorous and habitual rubbing of the eyes is strongly associated with keratoconus and with faster progression. Mechanical stress from rubbing is thought to contribute to corneal weakening.
• Allergic conditions. Eye allergies, allergic conjunctivitis, hay fever, asthma, and eczema (together known as atopy) are more common in people with keratoconus, partly because itchy eyes encourage rubbing.
• Certain genetic and systemic conditions. Keratoconus occurs more frequently in people with Down syndrome and in some connective tissue disorders, such as Ehlers-Danlos syndrome and Marfan syndrome, which affect the body’s collagen.
• Age. Onset is typically in adolescence or early adulthood, and progression tends to be faster in younger patients.

Keratoconus is not caused by reading, screen use, or wearing glasses, and it is not the result of an infection. While no known measure can prevent keratoconus entirely, avoiding eye rubbing and treating eye allergies effectively are widely recommended steps that may reduce the risk of progression.

Diagnosis

Keratoconus diagnosis is made by an eye doctor — typically an ophthalmologist (a physician specializing in eye disease) — using a combination of a clinical examination and specialized corneal imaging. Because early keratoconus can look like ordinary astigmatism, imaging technology plays a central role in confirming the condition and tracking whether it is progressing.

Common steps in the diagnostic process include:

• Vision testing and refraction. The doctor measures how well you see and determines your prescription. Rapidly increasing or irregular astigmatism raises suspicion of keratoconus.
• Slit-lamp examination. A slit lamp is a special microscope used to examine the eye. In more established keratoconus, the doctor may see corneal thinning, fine vertical stress lines in the cornea, an iron-colored ring around the base of the cone, or scarring.
• Corneal topography. This is a painless imaging test that creates a detailed color map of the curvature of the front surface of the cornea. It is one of the most important tools for detecting the irregular steepening typical of keratoconus, often before other signs appear.
• Corneal tomography. More advanced scanners map both the front and back surfaces of the cornea and measure its thickness at many points. Thinning and steepening of the back surface can reveal very early disease.
• Pachymetry. This test measures corneal thickness. A cornea that is thinner than normal, especially at or near the cone, supports the diagnosis and helps guide treatment decisions.

Doctors generally confirm keratoconus when imaging shows characteristic irregular steepening and thinning of the cornea, particularly when the findings change over time. Repeat scans performed months apart are often used to determine whether the condition is stable or progressing, which directly influences treatment choices. If you are being evaluated for refractive laser surgery (such as LASIK), screening for keratoconus is a routine and essential part of the assessment, because laser surgery that removes corneal tissue can seriously worsen an unstable cornea.

Treatment options

Keratoconus treatment has two separate goals: improving vision and, when the disease is progressing, stopping or slowing further weakening of the cornea. The right combination depends on the stage of the disease, whether it is progressing, the corneal thickness, and the patient’s visual needs. In hospital settings such as Acibadem, keratoconus is evaluated and managed within the ophthalmology department, where corneal imaging and the full range of treatments can be coordinated.

Observation and glasses in early disease

In mild, stable keratoconus, eyeglasses or standard soft contact lenses may still provide acceptable vision. In these cases, your doctor may recommend regular monitoring with corneal imaging — often every six to twelve months at first — rather than immediate intervention. Watchful waiting is appropriate only when scans show the condition is not progressing; if progression is detected, treatment to stabilize the cornea is usually discussed.

Specialized contact lenses

As the cornea becomes more irregular, glasses can no longer correct the distortion, because they cannot smooth out the uneven surface. Specialized contact lenses then become the main tool for improving vision:

• Rigid gas-permeable (RGP) lenses. These firm lenses rest on the cornea and create a smooth, regular optical surface, often improving vision considerably.
• Hybrid lenses. These combine a rigid center with a soft outer skirt to improve comfort.
• Scleral lenses. These larger lenses vault completely over the cornea and rest on the white of the eye (the sclera), with a fluid layer beneath. They are often used for moderate to advanced keratoconus and can be more comfortable for irregular corneas.

It is important to understand that contact lenses improve vision while worn but do not stop the disease from progressing.

Corneal cross-linking

Corneal collagen cross-linking (often abbreviated CXL) is the standard procedure used to slow or halt progression of keratoconus. During the procedure, riboflavin (vitamin B2) eye drops are applied to the cornea, which is then exposed to controlled ultraviolet (UV-A) light. This combination creates new chemical bonds between collagen fibers, stiffening and strengthening the corneal tissue. Cross-linking is generally recommended for patients with documented progression, and it is usually performed as an outpatient procedure. Its main purpose is stabilization, not visual improvement, although some patients notice modest flattening of the cone over time. Adequate corneal thickness is required, which is one reason early diagnosis matters.

Intracorneal ring segments

Intracorneal ring segments are small, curved implants made of a clear plastic material that a surgeon places within the layers of the cornea. They can flatten and regularize the cone to some degree, which may improve vision or make contact lens wear easier. Ring segments do not cure keratoconus and are sometimes combined with cross-linking. Suitability depends on corneal thickness and the shape and location of the cone.

Corneal transplantation

When keratoconus is advanced — with severe thinning, significant scarring, or vision that can no longer be usefully corrected with lenses — corneal transplantation may be considered. Two main approaches exist. In a full-thickness transplant (penetrating keratoplasty), the entire central cornea is replaced with donor tissue. In a partial-thickness transplant (deep anterior lamellar keratoplasty, or DALK), only the front layers are replaced while the patient’s own innermost layer is preserved, which may reduce certain rejection risks. Transplantation for keratoconus generally has favorable outcomes compared with transplants for other conditions, but recovery is gradual — visual rehabilitation often takes many months — and glasses or contact lenses are frequently still needed afterward. As with any surgery, risks such as graft rejection, infection, and astigmatism exist and should be discussed in detail with the treating surgeon.

Managing contributing factors

Alongside these treatments, doctors commonly advise patients to stop rubbing their eyes and to treat eye allergies, often with lubricating or anti-allergy eye drops, because ongoing rubbing may contribute to progression. There is currently no medication that reverses keratoconus itself.

Living with keratoconus and outlook

For most people, keratoconus is a manageable, long-term condition rather than a cause of blindness. Total loss of vision is very uncommon; even in advanced disease, treatments such as scleral lenses and corneal transplantation can usually restore useful vision, although results vary from person to person and no outcome can be guaranteed.

Progression tends to be fastest in the teenage years and twenties and often slows later in life, which is why younger patients are usually monitored more closely. With the availability of corneal cross-linking, many patients diagnosed early can have their disease stabilized before significant vision loss occurs, reducing the likelihood of eventually needing a transplant.

Practical points for day-to-day life include:

• Attend regular follow-up visits and repeat corneal imaging as recommended, even when vision feels stable.
• Avoid rubbing your eyes. If itching is a problem, ask your doctor about allergy management.
• Care for contact lenses properly to reduce the risk of infection, and report discomfort or redness promptly.
• Tell any eye surgeon about your keratoconus before considering laser vision correction, which is generally not suitable for keratoconic corneas.
• Discuss driving and occupational vision requirements with your doctor, particularly if night glare is troublesome.

Many patients adapt well once a stable lens fit or successful treatment is achieved and continue with normal education, work, and activities. Emotional adjustment can take time, especially for young people facing a changing prescription; honest conversations with the eye care team about realistic expectations often help.

Frequently asked questions

What is keratoconus in simple terms?

Keratoconus is a condition in which the clear front window of the eye, the cornea, becomes thinner and gradually bulges into a cone shape instead of keeping its normal round dome. This irregular shape scatters light entering the eye, causing blurred and distorted vision. It usually starts in the teenage years or early adulthood and often affects both eyes to different degrees.

Can keratoconus heal on its own?

Keratoconus does not heal or reverse on its own, and the corneal thinning that has already occurred is generally permanent. However, in many people the condition naturally slows or stabilizes with age, and treatments such as corneal cross-linking can often halt further progression. Vision that has been affected can frequently be improved with specialized contact lenses or, in advanced cases, surgery.

How serious is keratoconus?

The seriousness varies widely. Many people have mild disease that is managed with glasses or contact lenses for their entire lives. Others progress to moderate or advanced disease that requires cross-linking, specialty lenses, or eventually corneal transplantation. Keratoconus very rarely causes complete blindness, but untreated progressive disease can lead to significant vision loss, which is why early diagnosis and monitoring matter.

What are the first keratoconus symptoms people notice?

The earliest keratoconus symptoms are usually mild blurring, increasing astigmatism, and frequent changes in eyeglass prescriptions. Glare, halos around lights at night, and ghost images seen with one eye are also common early complaints. Because these symptoms overlap with ordinary vision changes, corneal imaging is often needed to confirm the diagnosis.

Does corneal cross-linking improve vision?

Cross-linking is primarily designed to strengthen the cornea and stop the disease from getting worse, not to sharpen vision. Some patients experience modest flattening of the cone and a small improvement over time, while others notice little change in how they see. Most people still need glasses or contact lenses after the procedure, and your doctor can explain what results are realistic in your specific case.

What is recovery like after keratoconus surgery?

Recovery depends on the procedure. After cross-linking, the eye is often uncomfortable and light-sensitive for several days while the surface heals, and vision may fluctuate for weeks. After a corneal transplant, healing is much slower: stitches may remain for many months, vision improves gradually, and full visual rehabilitation can take a year or longer. Follow-up visits and prescribed eye drops are essential parts of recovery in both cases.

Can I wear contact lenses if I have keratoconus?

Yes, in most cases. In fact, specialized contact lenses — including rigid gas-permeable and scleral lenses — are a mainstay of keratoconus treatment because they create a smooth optical surface over the irregular cornea. Fitting these lenses requires expertise and sometimes several adjustments, and good lens hygiene is important to avoid complications such as infection.

When to see a doctor

You should arrange an eye examination if your vision is becoming increasingly blurred or distorted, if your eyeglass prescription keeps changing over a short period, or if you notice glare, halos, or ghost images that interfere with daily activities. Teenagers and young adults with rapidly changing prescriptions, and anyone with a family history of keratoconus, benefit from evaluation that includes corneal imaging.

Seek urgent medical attention if you experience any of the following red-flag warning signs:

• Sudden clouding or whitening of vision in one eye, especially with pain and redness — this may indicate acute corneal hydrops
• Severe eye pain that does not settle
• A red, painful eye with discharge or worsening light sensitivity while wearing contact lenses, which can signal a corneal infection
• Sudden, marked drop in vision in either eye
• After a corneal transplant: new redness, pain, light sensitivity, or decreasing vision, which can be signs of graft rejection and need prompt assessment

Prompt evaluation of these symptoms can make a meaningful difference to the outcome. For ongoing management, keratoconus is typically followed by a corneal specialist within an ophthalmology department, where imaging, lens fitting, and surgical options can all be coordinated over time.