If you're a long time reader, you'll know I've dedicated a lot of articles to writing about specialty contact lenses for keratoconus because its the specialty I've chosen to pursue in my own eyecare practice. In the five years that I have been out of optometry school, I've fit hundreds of patients with specialty contact lenses for irregular corneas, and over and over I found myself wondering, how could I be seeing so many? A new study out of the Netherlands in 2016 has revolutionized how common we believe keratoconus to be, reporting a prevalence of 1 in 375 people.  Compare that to the previous estimated prevalence of 1 in 2000 reported in a 1986 study out of Minnesota, and you can see why the news has rocked the eyecare world. 

An eye with keratoconus and corneal scarring via

What is Keratoconus?
Eyecare specialists define keratoconus as "bilateral, asymmetrical, noninflammatory pathology characterized by progressive, localized thinning and protrusion of corneal tissue." In layman's terms, you'll often hear it described as a steepening of the cornea, causing the cornea to bulge forward and disrupt vision. One reason why we've struggled so much to both treat and properly define how prevalent keratoconus is in society is because we still have a poor understanding of what is happening in this disease. We know that the process of corneal thinning and protrusion usually starts around puberty, and progresses on average 10-20 years from there. Most people by age 40 have no further progression of the disease because of aging changes that stiffen and thus strengthen the cornea and prevent further prolapse. Keratoconus can be detected in its earliest stages with corneal topography, where the tell-tale surface steepening is visible creating a pattern of asymmetric and irregular astigmatism on the corneal surface. 

Corneal topography showing normal (regular) astigmsim on the left and irregular astigmatism caused by keratoconus on the right. Note the lack of symmetry vertically in this map - a giveaway of corneal dystrophy. via

Access to corneal topography is the big reason researchers think keratoconus was so greatly under reported in earlier population studies. In the 1986 study that reported a prevalence of 1 in 2000, doctors had to detect keratoconus based on irregularities seen on keratometry and during retinoscopy. These days, you'll be hard pressed to find an office with old-school manual keratometers, replaced with high tech corneal topography that can detect even subtle changes. With this newer technology, earlier and much milder forms of corneal irregularity can be detected. 

What We Know and What We Don't
For years doctors have theorized that keratoconus had a genetic component, but there has never been a gene found that definitively proved this. And population studies looking at genetic prevalence show mixed results. Environmental factors like allergies and chronic eye rubbing also appear to contribute. So if you are looking for a definitive answer to why you have keratoconus, the answer is not so simple. It's probably a mixture of environmental and genetic risk factors.

Here's what we do know:

• Keratoconus is more common in India, the Middle East, and China than other countries around the world. It is unknown if this is due to environmental difference in temperature, oxidative UV damage from being closer to the equator, or diet and nutritional differences.
• The genetic prevalence of keratoconus differs based on ethnicity.
• In the US, the genetic prevalence of keratoconus is between 6 and 13.5% depending on the study you look at. 
• When prevalence in a 2015 study was separated by ethnicity, Caucasians were found to have a genetic prevalence of 5% and Asians had 25% prevalence.
• Eye rubbing is an associated risk factor; chronic ocular allergies may be a risk factor (or is it just the rubbing?)
• People with keratoconus tend to rub their eyes longer and "more vigorously" than those with normal corneas. An average cornea patient tends to rub their eyes on average for 5 seconds and no longer than 15 seconds even when bothered by allergies; surveyed keratoconus patient rubbed their eyes between 10 and 180 seconds. Additionally, keratoconus is associated with:
• rotational knuckling motion with rubbing
• more forceful rubbing
• rubbing frequency greater than once a day
• rubbing year round (not just seasonal with allergies)
• Study results are mixed as to whether the risk of keratoconus is higher with a history of chronic allergies or atopic hypersensitivity like asthma and eczema. About 1/3 of patients with keratoconus self-report a history of allergies. 

An eye with keratoconus via

via

April 18th, 2016 was a life-changing day for people living with keratoconus in the USA; corneal collagen crosslinking, the revolutionary treatment that's been performed in Europe since 1999, was finally approved by the FDA. Keratoconus affects as many as 1 in every 500 people, causing potentially severe vision loss.  But it's progression and causes are poorly understood. During the disease process, the cornea tissue thins and weakens, causing the cornea to prolapse forward like a steepening mountain.  The resulting warpage and associated scarring wrecks havoc on vision, often requiring severely invasive procedures like full thickness corneal transplant as the condition worsens. In corneal collagen crosslinking, the goal is to stop the progression of keratoconus while the damage is still mild and vision is still usable, long before more aggressive surgical interventions would be needed. Using riboflavin and UV light, doctors are able to strengthen the connections of the collagen fibers of the cornea so that they hold tighter and stronger together, locking the cornea in place. 

Keratoconus causes progressive corneal steepening and is devastating to vision via

For patients diagnosed with keratoconus, accepting how little can be done with modern medicine to protect and preserve their quickly declining vision can be the most devastating part of the diagnosis. Our current treatment model in the world of keratoconus goes something like this: try to keep going in contact lenses as long as possible, and when even those can't do the job anymore, time for a corneal transplant. Many patients live with a possible visual doomsday hanging over their head -- that day where contact lenses just won't work anymore and they might have to accept that they are going blind or needing major, risky surgery. Luckily, new technologies are being researched and explored that can stabilize the cornea and help prevent further vision loss.  Both corneal Intacs and corneal cross linking are currently performed in the United States, and both can help stabilize the degenerative process behind keratoconus. Unfortunately, not everyone is a candidate for these surgeries.  Advanced keratoconus patients whose corneal curvature is steeper than 60D or whose cornea is thinner than 350 microns wouldn't be able to pursue either of these surgical options due to the risk of complications.  But new research by Dr. Gerrit Melles in the Netherlands and Dr. Jack Parker with UAB has demonstrated a possible intervention that would stabilize the corneas of even these higher risk patients: Bowman's layer transplantation.

via

Keratoconus: an irregular, protruding cornea.  Photo via clspectrum.com

In my last post about keratoconus, I mentioned a promising new treatment called corneal cross-linking.       This procedure is still undergoing FDA approval, but more and more ophthalmologists across the states are starting to offer this treatment. Because this procedure is so new in the States, there is still much to learn.  Here is a breakdown of the information I have about corneal cross-linking:

What is corneal cross-linking?

The cornea is made up a collagen fibers that are woven together to make a tight and strong (and clear!) tissue.  In keratoconus, these collagen fibers are somehow weakened, causing the cornea to become misshapen, irregular, and scar over.  This results in devastating vision loss.  Corneal cross-linking is a process where the collagen fiber connections are strengthened again, so that the cornea can maintain its shape and clarity.   Cross-linking actually happens naturally as we age (the collagen fibers tend to strengthen their attachments around age 40) which is why keratoconus tends to be a degeneration of the young eye, and stabilizes later in life.

The Treatment Procedure


I won't begin to go into exact details (this blog is for everyone, not technical scientists!), but the general process is easy to explain.  Your ophthalmologist will apply riboflavin to the eye (after they prepare your cornea to improve penetration of the liquid riboflavin into the deeper layers of the eye).  Then your eye is exposed to UV light for around 30 minutes, which causes the chemical "strengthening" reaction between collagen fibers.  Studies have shown that this procedure increases the corneal "rigidity" by 328%!  You will be conscious the entire time of the procedure and should experience no pain.

Cross-linking procedure.  Riboflavin has been applied, and now UV light is being shone on the eye. Photo via clspectrum.com

Benefits
Of all studies so far completed (about 691 eyes worldwide have been done), an impressive 92% of patients saw NO progression of their keratoconus 1 year after the procedure.  55% (up to 81% in some studies!) of people saw their vision improve by 1 line or more.  In summary: with this procedure, your eyes should stabilize, and may even improve a little.

Vision is usually worse right after the procedure, and for as long as 6 weeks afterward.  Improvement in vision will begin to be evident by 3-6 months after the surgery date.

Potential Risks
In rare cases (8% from the recent research), the cornea can develop a permanent haze.  To avoid this risk, the cornea needs to be over 400 microns thick (this is a measurement that the surgeon will take prior to performing the procedure).

Who is a candidate?
Corneal cross-linking is ideal for patients with keratoconus who are under 35.  It can also be considered in older patients if their keratoconus is progressing.  You will still need glasses or contact lenses after the procedure, and your prescription may change afterwards.

Cost?
Because it is not yet FDA approved, the procedure is not covered by medical insurance.  Costs across the nation are $3-6,000.

In North Carolina, Dr. Patrick Laber is now offering the procedure.  (Most information provided in this post is courtesy of his detailed explanations!)

Everyday I see patients who are coming to the eye doctor for the first time in years because they noticed they just weren't seeing as well as they used to.  Well imagine what it feels like when the doctor looks at your screening tests and performs the refraction, and then tells you that you have a medical condition that will prevent you from seeing better, even with glasses!  Keratoconus is a condition that affects less than 1% of the American population, but it causes major visual issues that sometimes require intensive surgery like corneal transplants to treat.  It typically affects people between their late teens to late 30s, and usually progressively worsens as the eye continues to change with age up until our 40s, when the condition appears to stabilize.  In that period of 20 years where the cornea is susceptible to progression, people often end up needing surgery or at least speciatly contact lenses to achieve their best vision.

Me: "Have you ever been diagnosed with any eye diseases like glaucoma or macular degeneration?"
Patient: "Yes-- I had a doctor tell me that I have that 'stig....stigmatism"
Or
Patient: "So what is wrong with my vision?"
Me: "Well today we have found some changes due to cataracts, but we can improve your vision by increasing your astigmatism correction in your glasses." 
Patient: "Oh no!  I have astigmatism!!?"

Multiple points of light fall onto the retina in Astigmatism.

The inner circle of the phoropter is used to refine the axis

Keratoconus causes large amounts of astigmatism and usually requires specialty contact lenses or even a corneal transplant