Vision starts with a functional, clear cornea (the front ‘window’ of your eye). Without a clear cornea the rest of the refractive media in the eye, like the lens, can not function properly. Correcting corneal irregularities can improve your vision.
What is keratoconus?
Keratoconus is a non-inflammatory eye condition in which the normally round dome-shaped cornea (clear window of the eye) progressively thins causing a cone-like bulge to develop.
Changing the shape of the cornea brings light rays out of focus. As a result, your vision is blurry and distorted, making daily tasks like reading or driving difficult. Keratoconus can cause significant visual impairment.
Left image: An eye with a normal cornea. The clear window at the front of the eye.
Right image: An eye with keratoconus, where the cornea bulges out like a cone.
What causes keratoconus?
Doctors do not know for sure why people have keratoconus. It appears to be a combination of allergies, genetic (passed down in families) and other factors. About 1 out of 10 people with keratoconus have a parent who has it too. Keratoconus is often first diagnosed when people are in their late teens to early 20s. The vision symptoms slowly get worse over a period of about 10 to 20 years and then stabilize or slow down. Each eye is not necessarily affected the same.
DO NOT RUB YOUR EYES!
Avoid vigorous rubbing of your eyes. This can damage thin corneal tissue and make your symptoms worse. If you have the urge to rub your eyes due to itching, speak to your ophthalmologist about medicines to control your allergies.
What are keratoconus symptoms?
Keratoconus often affects your two eyes differently and symptoms can change over time.
In its earliest stages keratoconus symptoms can include:
Mild blurring of vision
Distortion of vision, where straight lines look wavy
Increased sensitivity to light and glare
Eye redness or swelling
In later stages keratoconus symptoms often include:
Even more blurry and distorted vision
Increased nearsightedness or astigmatism (As a result, you may need a new prescriptions for glasses often)
Not being able to wear contact lenses (They may no longer fit properly and they are uncomfortable)
Keratoconus usually takes years to progress to late stage. Sometimes keratoconus can get worse quickly. The cornea can swell suddenly and scars can form. When the cornea has scar tissue, it is less smooth and becomes less clear. Vision grows even more distorted and blurry. With late stage keratoconus glasses and scleral contact lenses may no longer correct your vision.
How is keratoconus diagnosed?
Keratoconus can be diagnosed during a routine eye exam. Additional tests may be necessary. During Keratometry your eye doctor focuses a circle of light on your cornea and measures the reflection to determine the basic shape of your cornea.
Special photographic tests, such as optical coherence tomography and corneal topography, record images of your cornea to create a detailed shape map of your cornea’s surface. The tests can also measure the thickness of your cornea. These results aid in the decision of your treatment.
How is keratoconus treated by optometrist?
Scleral Contact Lens
Keratoconus treatment depends on your symptoms. When your symptoms are mild, your vision can be corrected with glasses. Later you may need to wear special hard contact lenses called scleral lenses to help keep vision in proper focus.
Your optometrist will refer you to an ophthalmologist if:
Your spectacle prescription deteriorates by more than one diopter in sphere (near or far sightedness) or cylinder (astigmatism) in one year.
You have keratoconus and become contact lens intolerant.
How is keratoconus treated by ophthalmologist?
Different procedures can be combined:
1. With collagen cross linking your ophthalmologist uses a special UV light and eye drops to strengthen the tissues of the cornea. Doing this helps to flatten your cornea, keeping it from bulging further. It also slows down progression.
Before Cross Linking
After Cross Linking
2. An intra-stromal corneal ring segment is a very small curved device that your ophthalmologist puts in your cornea with the help of a femto-second laser. These ring segments help flatten the curve of your cornea to improve vision.
Intra-stromal Corneal Ring Segment
3. Photorefractive keratectomy (PRK) is laser surgery and corrects mild to moderate refractive error left after cross linking and corneal intra-stromal rings.
4. Intra ocular lenses can correct from low to high refractive error associated with keratoconus.
For optimal results these procedures are combined depending on the specific case:
The Athens protocol addresses the irregular cornea at the time of cross linking. This consists of combined, same day, topography guided partial PRK and collagen cross linking. This does not only stabilize the cornea but also improves vision.
Double procedures (Corneal ring & Cross linking or Cross linking & Intra ocular lens)
Triple procedure (Corneal rings followed by cross linking and PRK or Intra ocular lens)
Four-Stage procedure includes all four of the abovementioned treatment options For older patients one can also stabilize the cornea with cross-linking & corneal rings followed by cataract surgery with an intra ocular lens to improve refraction further.
Corneal transplant for advanced keratoconus
When symptoms are severe, your ophthalmologist may suggest a corneal transplant. This surgery replaces all or part of your diseased cornea with healthy donor cornea tissue. For keratoconus patients the options are:
Penetrating Keratoplasty (PKP) – The full thickness of the central part of cornea is replaced with donor cornea and sutured in place. Sutures are removed after one year and vision improves over this period. One year later additional refractive laser surgery may be necessary to further improve vision.
Deep Anterior Lamellar Keratectomy (DALK) – Only the outer layers of the central part of the cornea is replaced with donor cornea. Keratoconus patients are usually young with a healthy endothelium. With this procedure there is no graft rejection. Similar to PKP sutures are removed after one year and refractive surgery may be necessary another year later.