Keratoconus – Definition & Overview

Keratoconus, pronounced (ker-uh-toe-KOH-nus), is a chronic, degenerative disease of the cornea where it starts thinning and bulges out into a cone shape as opposed to its normal round shape. The adjacent illustration shows a side view of a normal round shaped cornea versus a cone shaped, keratoconus cornea. The explainer type video below provides information which shows you all about keratoconus.  We also have a short summary of how we help our patients with keratoconus.

Side view illustration of a normal round-shaped cornea versus a diseased keratoconus cornea
Close up of an man's eye with keratoconus

The cornea is the clear tissue covering the front of the eye, both the iris and the pupil.  Its main purpose is to direct light onto the retina for clear vision.  As the cornea weakens, it can no longer maintain its normal curvature against the internal eye pressure.  Thus, the cornea bulges out, causing astigmatism.   This change in structure affects the person’s eyesight, so that images start blurring, which occurs at all distances, causing myopia (nearsightedness) as well as hyperopia (farsightedness).  The adjacent photograph shows a close-up view of a man’s eye with keratoconus. Note the obvious cone-shaped cornea of the patient.

Keratoconus only affects about 1 in 2000 people, so the rate of disease is low.  The current US population is about 330 million, so by calculation, the US has about 165,000 keratoconus sufferers.  But its effects can be devastating as it can cause blindness. It typically affects both eyes, however, usually not to the same degree.  Below is a short news video about Golden State Warrior’s NBA superstar Steph Curry’s battle with keratoconus.  Since he started wearing scleral contact lenses, his game has gotten significantly better, if you can believe that!  It also shows what keratoconus is and how it affects your eyesight.

Cause & Risk Factors

Although a significant number of studies have been performed, the definitive cause of keratoconus is still not well understood.  The risk factors given below are related to a predisposition for keratoconus.

Age 

For those individuals with keratoconus, typically it starts just after childhood, during puberty in adolescence and can progress until young adulthood, about 25-35 years old.  Although in some people it never becomes progressive, so in that way, it’s an enigma.

Genetics

There is a genetic component, as about 10% of the cases have at least one parent who also has the disease. A family history of Down’s Syndrome and asthma also increases your risk.

Chronic Eye Inflammation & Rubbing Your Eyes

Those whose eyes are continually inflamed are more susceptible to keratoconus. The inflammation causes irritation and pain resulting in eye rubbing. Chronic eye rubbing is thought to be a major cause of keratoconus progression.  The image below shows a patients inflammed eye exacerbated by eye rubbing.  

Close-up photograph of an eye with severe eye inflammation

Other Risk Factors

Keratoconus  also is associated with eye injuries, eye allergies and connective tissue disorders such as Marfan syndrome and Ehlers-Danlos syndrome. Other eye diseases like retinitis pigmentosa increase its risk as well.

Prevention & Cure

Unfortunately at this time, we do not know how to prevent keratoconus and there is no known cure. In addition, in the early stages, some people may not realize that they have it. This makes it incredibly important to make an appointment for an eye examination with your eye doctor for early diagnosis and treatment of keratoconus.

Keratoconus Symptoms

If you have one or more of the symptoms listed to your right, contact your optometrist at Good Eye Optometry to schedule a comprehensive eye examination to determine the cause. It may not be significant, but it’s a good idea to find out sooner rather than later.

$

When you look at lights, you see halos or glare around them

$

You develop a sensitivity to bright lights

$

Your night vision is impaired

$

Your vision becomes distorted or blurred

$

Your eyeglasses or contact lenses prescription change frequently

$

Your vision suddenly gets worse or vision clouds

Diagnosis

All eye care tests should be preceded by a thorough medical history and then a comprehensive eye exam to determine visual acuity and detect potential eye abnormalities. There are a couple of ways to diagnose keratoconus. The most accurate tool with the latest technology is a corneal topography machine in which a computer-assisted 3D map of your cornea is created from thousands of digital measurements. This method is non-invasive, painless, and only takes a few minutes while you stare into a concave cone. The corneal topography machine is shown in the adjacent photograph where the test is about to begin.

corneal topography machine to measure the cornea's thickness
corneal topography test results displayed on the computer screen

A sample image of the results from the corneal topography test is shown in the image on your left where the varying thickness of the cornea are color coded. These results are from a patient with severe keratoconus as shown by the large red area indicating steepness of the cornea in that area. This is explained in detail in the short video on corneal topography below.

A slit-lamp machine can detect corneal anomalies by measuring the middle and outer layers of the cornea. So it too can diagnose keratoconus. In this test, your eye doctor shines a bright light into your eye while looking through a microscope to evaluate your cornea. It is non-invasive and painless as well.

While there are other methods to measure your cornea, these are the primary tests.

eye slit-lamp exam being performed on a young girl

Treatment

We do know that treatment for keratoconus is essential so that it does not result in permanent vision loss. The treatment goals are correcting vision and minimizing disease progression. Treatment is determined by the stage of progression of the disease; early, intermediate, or advanced.

Early

In the very early stages of keratoconus, people may not even know that they have the disorder. This is one reason why regular periodic eye exams are highly recommended.
When keratoconus is first diagnosed in its early stage, the strategy is to correct your vision and obtain baseline data so we can determine its progression over time. At this point, your doctors may just order eyeglasses or soft contact lens prescription to increase visual acuity.

Intermediate

Scleral Contact Lenses

If your keratoconus progresses to the intermediate stage, eyeglasses and soft contact lenses probably can no longer correct your vision. Scleral contact lenses are a great option which are custom made to fit each patient’s eye. Therefore, they are more expensive than normal contact lenses. Scleral lenses are hard, gas permeable contacts with a large diameter, so they can vault over the cornea and rest on the sclera, the white part of the eye. Even though large, scleral lenses are quite comfortable because the sclera has many fewer nerve endings when compared to the cornea. The area between the inside of the contact and the cornea is filled with a saline solution that helps with vision correction. The video below shows an interview with patient, Larissa, who explains that her scleral contact lenses are a godsend.

Collagen Cross-Linking

The great news is that the cornea can be strengthened by a relatively new process called collagen cross-linking or corneal cross-linking. The procedure was approved by the FDA in 2016 after clinical trials proved its efficacy. It is the only technique that has been shown to halt or slow keratoconunus progression. In some cases, it improves the curvature of the cornea and becomes more normally shaped as it strengthens. Vision improves in many patients that undergo this procedure. Collagen, a protein, is an important component of the middle section of the cornea which adds strength and flexibility to the cornea. In keratoconus, some of the collagen in the cornea is lost, causing weakness. This one-time procedure is performed by an ophthalmologist in the office where the eye is bathed in a Vitamin B2 (riboflavin) solution while ultraviolet light activates the collagen to cross link to other collagen molecules by forming strong chemical bonds. In the news interview below, Dr. Ryan Turner explains how this technique is being used to help keratoconus patients. In the next video Dr. Terrence Doherty of Loden Vision Centers in Nashville, TN walks you through a collagen cross-linking procedure with patient Michael.

Advanced

If keratoconus reaches the advanced stage, you have two basic options, both of which involve eye surgery performed by an ophthalmologist.

 

Corneal Ring Implant

If your keratoconus becomes severe and contact lenses are causing too much pain, you may be a candidate for corneal ring surgery. Plastic, c-shaped rings are surgically inserted into the middle layer of the cornea to add strength, structure, and flatten your cornea. Other common names for these rings are INTACS® or ICRS. The procedure takes place in an outpatient surgical center. It’s quick, about 15 minutes per eye, simple and painless. Vision correction typically is quite dramatic as a patient goes from unable to read to almost everyone can pass the driver’s license eye exam without eyeglasses and about half the patients have 20/20 vision.

Corneal Transplant

A corneal transplant may be necessary if your keratoconus progresses to the advanced stage, and you are not a candidate for corneal ring implant. For example, if your cornea has scarring or traumatic injury. The surgery usually takes place as an outpatient and takes about an hour per eye. Your cornea is excised and replaced with a donor cornea. The biggest issue is preventing tissue rejection, but despite this, it has a 95% success rate, one of the highest success rates of all transplant surgeries. In most cases, the patient will still require corrective lenses even after transplant.

Conclusion

Close-up of a young woman's eye before and after dry eye treatment

If you think you are experiencing any of the signs or symptoms of keratoconus, please make an appointment with us today at Good Eye Optometry.  Our optometrists have many years of experience working with and successfully managing keratoconus patients.  Remember, early diagnosis is very important so we can monitor its progression and recommend the proper treatment. 

For more information on keratoconus, go to the National Keratoconus Foundation at https://nkcf.org, the American Academy of Ophthalmology at https://www.aao.org, or the American Optometric Association at https://www.aoa.org/healthy-eyes/eye-and-vision-conditions/keratoconus/.

Get in Touch!