What You Should Know About Keratoconus

What is Keratoconus?

Keratoconus (KC) is a condition that affects the shape of a person’s cornea, which is the clear outer lens or "windshield" of the eye.

Over time, the cornea thins and bulges, progressively getting worse. It can lead to nearsightedness (myopia), blurred vision that cannot be improved with eyeglasses (irregular astigmatism), and vision loss.

It is also known as bulging cornea, conical cornea, and KC. Estimates are that keratoconus affects 1 in 500 to 2,000 individuals worldwide.

Source: All About Vision

In many cases of keratoconus, iron deposits can form in the cornea to produce a yellow or brownish ring. That is known as Fleischer ring and appears around the iris (the colored part of the eye).

Individuals with keratoconus may also develop thin, vertical white lines on the back of the corneal tissue (Vogt's striae).

One eye may be affected at first, but eventually, the corneas of both eyes will become misshapen. The degree of severity in each eye is independent of the other eye.

Because people often wear contact lenses in an attempt to lessen the impacts of keratoconus, or because of excessive eye rubbing, corneal scarring often occurs.

Typically, keratoconus begins in adolescence and continues to get worse until mid-adulthood. At this point, the cornea usually stabilizes.

KC affects between 5-15% of people with Down syndrome and has an impact on the ability function at the highest level ¹.

Screening for keratoconus during the teen and early adult years is critical to ensure that the debilitating effects of this condition can be countered as quickly as possible.

Causes of Keratoconus

There are many theories about the cause of keratoconus, but more research needs to be done before to verify theories about how it takes root.

Researchers generally believe that genetics, the endocrine system, and the environment all play a role in keratoconus.

Some researchers believe that keratoconus is developmental and caused by genetic inheritance ². Based on the best available research, there is less than a 10% chance that a blood relative of a person with keratoconus will also have the condition.

Other possible causes include eye rubbing and allergies. Minor eye trauma can cause more damage to a susceptible cornea. It is not clear whether eye rubbing leads to keratoconus or if eye rubbing is a response to discomfort in the early stages of the condition.

Others believe that poor fitting contact lens may be a cause because they rub against a cornea and worsen a mild condition. But these ideas have not been proven and are treated as questionable in many quarters.

Allergies that cause itching eyes that lead to vigorous rubbing have also been reported by keratoconus sufferers. There is a link between a higher percentage of keratoconus patients with an atopic disease than the general population.

Atopic diseases include disorders such as hay fever, eczema, asthma, and food allergies.

Keratoconus also is associated with overexposure to the sun’s ultraviolet rays.

Other studies have been able to link keratoconus to abnormal processing of the superoxide radicals in a cornea due to an imbalance of enzymes ³. This oxidative stress may also be a pathogenesis of this disease.

Like all bodily tissues, the cornea creates harmful byproducts of cell metabolism called free radicals.

Normal corneas have a defense system in place to neutralize the free radicals, so they don't damage the collagen in the cornea. When collagen weakens, it causes the cornea to thin and bulge.

Corneas with keratoconus don’t possess the ability to eliminate free radicals. As a result, they stay in the tissue and can cause structural damage.

Another controversial hypothesis is that hormonal changes may cause keratoconus. The endocrine system may be involved because keratoconus is generally first detected at puberty and progresses during pregnancy. This theory is still unproven, though.

The Genetic Pattern of Inheritance of Keratoconus

In some cases, keratoconus is hereditary; the predisposition to develop keratoconus passes from one generation to the next. If you have keratoconus, it's best to have your children checked for the condition starting at age 10.

The disease can progress at different rates in individuals, so it's best to be proactive if you or a loved one are at a higher identified risk.

Keratoconus can be a symptom of several other genetic syndromes. It has been associated with GAPO syndrome, Ehlers-Danlos syndrome, Down syndrome, Leber congenital amaurosis, Marfan syndrome, and arterial tortuosity syndrome.

The association with mental retardation and KC is common. In all, more than two dozen syndromes are associated with KC. When it is a part of another syndrome, keratoconus is caused by the same genetic mutation that causes the syndrome.

More than a dozen genes have been associated with developing keratoconus. Many of these gene mutations are found in small populations of the public and sometimes only in single families.

These genes serve a variety of functions but most often are associated with:

• eye development
• formation and structure of the cornea
• an extracellular matrix which is the highly detailed lattice of proteins and other molecules that forms in the space between cells
• an immune system response (inflammation)
• the regulation of cell growth

When any of these genetic functions are disrupted, sometimes in combination with environmental irritations, researchers believe this can trigger keratoconus.

The trigger varies. Sometimes it can be mostly genetic, and at other times it can be primarily environmental.

Signs and Symptoms of Keratoconus

Keratoconus starts in one eye most of the time but eventually affects both eyes. However, the level of vision in each eye may vary widely. Exact symptoms can also differ in each eye, and they may also change over time.

Onset usually starts in the teenage years, but it can begin in childhood or in people who are up to 30 years old. Cases of keratoconus starting as late as 40 have also been reported, but those instances are rare.

Early-stage symptoms of keratoconus include mildly blurred vision, eye strain, increased sensitivity to light, eye redness, eye swelling, and distorted vision where straight lines can look bent or wavy.

Seeing halos, ghosting, light streaking, problems with glare, and night vision issues are also common. Many people also report headaches and general eye pain, eye irritation, excessive eye rubbing.

Most people who develop keratoconus also have a history of nearsightedness. As it advances, astigmatism may also develop and get worse over time.  

As it progresses, keratoconus can produce increased distorted or blurry vision, more pronounced nearsightedness or astigmatism, or sudden swelling that can lead to corneal scarring.

This scarring means a cornea is no longer smooth and results in a more distorted and blurry vision. 

When stretched collagen fibers produce scarring, if the back of the cornea tears, it can take months and sometimes years for the swelling to go away. At this point, a corneal transplant may be one course of treatment.

In most cases, the condition progresses slowly and can take years to go from a mild case to a late-stage case. But every patient is different, and sometimes keratoconus can get worse in a short timeframe.

Many people with keratoconus have to change their eyeglass prescription every time they visit their eye doctor.

Every case is different, and there is no way to predict how keratoconus will advance and at what rate.

Potential Complications

When keratoconus is not treated, the cornea may become so thin that a hole will develop in the weakest part ⁴.

Another complication is that your eye may reject a corneal transplant ⁵. While this does occur, rejection rates for corneal transplants are much lower than with other organ transplants.

If you have keratoconus to any degree, never have laser correction surgery (i.e., LASIK)

Diagnosis of Keratoconus

In most cases, keratoconus is diagnosed through a routine eye exam. An ophthalmologist will examine the curve of your cornea to see if there is a change in its shape. A more accurate test is corneal topography. This is a computer-generated map of the curve of a cornea.

Children of parents with keratoconus should have a cornea topography test yearly starting at age 10. Even if the results are normal, it's still important to have this test performed annually.

This establishes a baseline that can be compared to identify changes when and if they start.

For later diagnosis in the later stages of the disease, an eye doctor may perform a slit-lamp exam. 

The thickness of the cornea can also be measured by undergoing a pachymetry test.

In families where keratoconus is already present in other family members, genetic testing can be an option to determine if a child is a carrier of any mutated genes associated with the disease.

Mutated genes with other syndromes may also cause keratoconus. Screening for these mutated genes can indicate if developing keratoconus is possible by being passed from one family member to another.

Although several studies have documented the linkage of keratoconus and genetic factors, the specific genetic factors remain elusive.

Patients with atopy (asthma and eczema) or severe ocular allergies are also at a higher risk of developing KC. 

Monitoring higher-risk patients should also be undertaken due to a possible hormonal link. This is because it is more frequent during puberty and also may progress during pregnancy.

Treatment and Care Options for Keratoconus

Young people whose vision cannot be corrected to 20/20 with glasses should be screened for keratoconus. Parents with keratoconus should have their children screened for the condition starting at age 10.

 More than 170 drugs are either in development or have been approved to treat the various forms of keratoconus ⁶.

There are several options to treat keratoconus. The optimal treatment will vary depending on how serious the condition is.

Eyeglasses or soft contact lenses may help with a mild case of keratoconus. But as the disease grows progressively worse as the cornea thins and becomes more irregular in shape, other more aggressive treatments will be required.

Those treatments may include ⁷:

Corneal crosslinking

Also referred to as CXL or corneal collagen crosslinking, the procedure strengthens the corneal tissue to stop bulging of the eye’s surface. Crosslinking increases the number of anchors that bond collagen fibers together.

There are two kinds of corneal crosslinking.

Epithelium-off. The outer layer of the cornea is called the epithelium. With this procedure, it is removed and riboflavin is inserted into the eye. It is then activated with UV light.

Epithelium-on. This is also referred to as transepithelial crosslinking. In this procedure, the corneal epithelium is left intact during the treatment. That results in less risk of infection, less discomfort, and recovery in a day or so.

One of the major benefits of corneal crosslinking is that it can significantly reduce the need for corneal transplants.

The combination of corneal crosslinking and Intacs implants has also proved to be an effective treatment for progressive keratoconus.

Crosslinking is also a prescribed course of treatment following LASIK or other types of refractive eye surgery.

Crosslinking can result in a serious eye infection known as ulcerative keratitis.

The most common ocular side effect of crosslinking is haze. Other side effects may include inflammation, fine white lines, dry eye, disruption of surface cells, eye pain, light sensitivity, reduced sharpness of vision, and blurred vision.

Discuss these risks should with your eye health care provider before seeking any corneal crosslinking treatment.

Custom soft contact lenses

Custom soft contact lenses specially designed to correct mild to moderate Keratoconus are made after detailed measurements of a patient's eye are taken. Patients have reported that these lenses are more comfortable than gas permeable or hybrid contact lenses in some cases.

Lenses can be made to fit a wide range of parameters. They are larger in diameter than regular soft lenses to provide more stability for an affected eye.

Gas permeable contact lenses

Gas permeable lenses are often a popular choice when eyeglasses and soft contact lenses can't get the job done. Gas permeable lenses vault over the cornea, producing a smooth and uniform refracting surface that improves vision.

However, fitting eyes with gas permeable lenses can take some time to accomplish. You may need to return to your eye care provider several times so that your prescription can be dialed in for maximum visual acuity.

That can be especially challenging if your keratoconus continues to change and progressively gets worse.

Sometimes, gas permeable lenses are uncomfortable for a person with keratoconus. As a result, some eye care professionals may suggest piggybacking to different types of contact lenses for the same eye.

This involves placing a soft contact lens over the eye and then layering in a gas permeable lens over the soft lens. The soft lenses act as a cushion under the rigid gas permeable lens, providing the wearer with a higher degree of comfort.

Your eye doctor will monitor the piggybacking lenses to make sure enough oxygen is reaching the eye. However, in most cases, this is not a major concern.

Hybrid contact lenses

Another version of a piggybacked lens system is a hybrid contact lens. A single lens combines a 

highly oxygen-permeable rigid center with a soft peripheral "skirt" for increased comfort. This single lens gives the wearer the crisp optics of a gas permeable lens and the comfort provided by wearing a soft lens.

Scleral and semi-scleral lenses

These are large-diameter gas permeable contacts that cover the periphery of the eye. The edge of the lens rests on the sclera or "white" of part of the eye.

Scleral lenses cover a larger portion of the sclera. Semi-scleral lenses cover a smaller area. Because they are larger than conventional gas permeable lenses, these are more stable.

Also, because the center of these lenses vaults over an irregularly shaped cornea, they don't apply pressure to the eye's cone-shaped surface, resulting in a more comfortable fit. 

Prosthetic lenses

Prosthetic lenses are used in patients with advanced keratoconus. Using advanced scanning technology, an eye impression captures the precise curvatures of a patient’s entire ocular surface.

The 3-D scanned data is fed into a precise machining system to produce a lens that matches the impression exactly, creating a perfect fit for a person’s cornea and sclera.

This technology is like a human fingerprint in that it is highly individualized. Prosthetic lenses can only be fitted by doctors who complete specific training and certification.

Intacs

Intacs by Addition Technology is FDA-approved clear, arc-shaped corneal inserts. They are surgically placed in the peripheral cornea to reshape the front surface of the eye.

They are sometimes needed with keratoconus patients no longer have a functional vision with eyeglasses or contact lenses.

The surgical procedure only takes about 10 minutes and can result in the best spectacle-corrected visual acuity (BSCVA) of an affected eye by an average of two lines on a standard eye chart.

Intacs can delay the need for a corneal transplant but can’t prevent it if keratoconus keeps getting progressively worse.

Topography-guided conductive keratoplasty

This treatment uses energy from radio waves that are applied with a small probe at several points in the periphery of the cornea to reshape the eye's front surface. It is a fairly new treatment still being studied to determine how effective it is in smoothing irregular features on the corneal surface.

Corneal transplant

When other treatments have failed, or a patient can’t tolerate a rigid contact lens, the last remedy option for many people is a corneal transplant.

There are two main types of cornea transplants:

• traditional, full thickness cornea transplant (also known as penetrating keratoplasty, or PK) 
• back layer cornea transplant (also known as endothelial keratoplasty, or EK).

The procedure is safe and has been available for a long time. In fact, since 1961, more than 1 million people have undergone a corneal transplant to restore their sight. The surgery takes one to two hours, and most procedures are performed on an outpatient basis.

Full recovery can take some time, as much as six months to a year.

There are two kinds of corneal transplant surgeries.

 The Penetrating Keratoplasty (PK or PKP) is the traditional transplant procedure, and patients are likely to obtain excellent correctable vision.

A newer technique is the Deep Anterior Lamellar Keratoplasty (DALK). It is a more delicate "partial-thickness" transplant. Only the top or outer layers of the damaged cornea are replaced.

This procedure is less invasive than a PK because there is a quicker recovery time and a decreased chance of graft rejection.

The Prognosis of Keratoconus

In most cases, vision can be corrected with rigid gas-permeable contact lenses. In many cases, keratoconus will stabilize after a few years.

However, in other cases, the disease will continue to worsen, and there may be additional health impacts that will necessitate more involved treatments.

If corneal transplantation is needed, results are very often good, but post-surgery recovery can take a long time. Many people may still need contact lenses even after surgery.

It's also important to note that while keratoconus can degrade vision to the degree that a person may have trouble leading a normal life, it typically does not lead to complete blindness.

A wider range of treatment options, better diagnostic and monitoring tools, and a better understanding of the underlying pathology of KC means that the prognosis of this condition has improved considerably over the past decade.

What to do Next: Living with Keratoconus

The worst thing you can do is ignore the signs and symptoms of keratoconus. Your best bet is to keep in regular contact and follow prescribed treatments for your condition. While there is no cure, several of the impacts of KC can be mitigated with proper care.

If you are struggling with acceptance of the disease, seek therapy, or find a support group.

The National Keratoconus Foundation also offers an online interactive forum where people can share experiences and information about this condition.

Researchers from Washington University in St. Louis and Ohio State University modeled a hypothetical cohort of patients to estimate the financial burden of KC after diagnosis.

They estimated an average cost of $20,000-$25,000. Much of the cost involves clinical care, specially designed contact lenses that are more costly than those used for routine vision correction, and possible surgical interventions such as Intacs or a corneal transplant.

Many state and national resources regularly provide financial aid for people who need help paying for vision problems ⁸.

EyeCare America is a public service foundation of the American Academy of Ophthalmology (AAO). It offers comprehensive eye exams and care for up to one year, often at no out-of-pocket expense to eligible callers.

VISION USA, coordinated by the American Optometric Association (AOA), provides free eye care to uninsured, low-income workers, and their families. 

Lions Clubs International provides financial assistance for eye care through local clubs. 

Knights Templar Eye Foundation assists in eye surgery for people who are unable to pay or receive adequate assistance from government agencies or other sources. 

National Keratoconus Assistance Foundation provides financial support to patients who need surgical and optometric treatment for keratoconus and other corneal problems. 

InfantSEE® is a public health program that ensures early detection of eye conditions in babies. Member optometrists provide free comprehensive eye assessments to children younger than one year. 

Keratoconus Support Organizations

The Global Keratoconus Foundation

Keratoconus Group 

Keratomania: Keratoconus Support and Awareness 

The National Organization for Rare Disorders (NORD) 

The National Eye Institute (NEI)

Online Mendelian Inheritance in Man (OMIM) (targeted to health care professionals and researchers, maintained by Johns Hopkins University School of Medicine)

PubMed is a searchable database of medical literature and lists journal articles that discuss keratoconus.

The Monarch Initiative

ClinicalTrials.gov lists trials that are related to Keratoconus.

MedlinePlus (designed by the National Library of Medicine)

The Merck Manuals Online Medical Library provides information for patients and caregivers.