Keratoconus

Keratoconus, often abbreviated to ‘KC’, is a non-inflammatory eye condition in which the normally round dome-shaped cornea progressively thins causing a cone-like bulge to develop.  A cone-shaped cornea causes blurred vision and may cause sensitivity to light and glare. Keratoconus generally begins to first affect people ages 10 to 25. It usually affects both eyes but often the progression is asymmetrical. The condition may progress slowly for 10 years or longer.

The disease is characterized by thinning and conus-like protrusion of the cornea. At first, the protrusion occurs in the inferior parts (lower half) but later on it also affects the central part of the cornea. 

The exact cause of keratoconus is unknown. There are many theories based on research and its association with other conditions. However, no one theory explains it all and it may be caused by a combination of things.

Risk factors

It is believed that genetics, the environment and the endocrine system all can increase your chances of developing keratoconus 

Genetic Factor:

• One scientific view is that keratoconus is developmental (i.e., genetic) in origin because in some cases there does appear to be a familial association. However, from the presently available information there is less than one in ten chance that a blood relative of a keratoconus patient will have keratoconus.

Environmental Factor: 

• Eye Rubbing: Keratoconus corneas are more easily damaged by minor trauma such as eye rubbing. Poorly fit contact lenses (that rub against the irregularity of the KC cornea) have been suggested as a possible cause of keratoconus; this has not been proven and remains questionable.

• Allergies: Many who have keratoconus report vigorous eye rubbing and also have allergies (which cause eye itching and irritation, leading to eye rubbing), however the link to allergic disease also remains unclear. A higher percent of keratoconic patients have atopic disease than the general population. Those with KC are advised to avoid eye rubbing as much as possible.

• Oxidative Stress: Some studies indicate an abnormal processing of the superoxide radicals in the keratoconus cornea and an involvement of oxidative stress in the pathogenesis of this disease. Keratoconus corneas lack the ability to self-repair routine damage easily repaired by normal corneas. Also, the keratoconus corneas do not possess the ability to eliminate the free radicals so they stay in the tissue and can cause structural damage.

Hormonal:

• Another hypothesis is that the endocrine system may be involved because keratoconus is generally first detected at puberty and progresses during pregnancy.  This theory is still controversial and has not been proven.

Symptoms and Diagnosis

Symptoms of keratoconus generally begin in late teenage years or early twenties, but can start at any time.  Signs and symptoms of keratoconus may change as the disease progresses. 

Driving at night can be difficult 

• Blurred or distorted vision 
• need for frequent changes in eye glass prescription, or blurred vision that cannot be corrected with glasses.
•  Increased light sensitivity
• Difficultly driving at night
• Halos and ghosting especially at night
• Headaches and general eye pain
• Eye irritation, excessive eye rubbing 

Keratoconus is commonly associated with other health disorders. Eye conditions include; allergic eye disease, retinitis pigmentosa, ocular rosacea, cone/rod dystrophy and corneal granular dystrophy. Other bodily conditions would include eczema or hay fever, Down’s Syndrome, and connective tissue disorders. Keratoconus has also been linked to forms of eye trauma including contact lens wear and eye rubbing. Diabetes has been shown to increase the severity of the condition.

When to see a doctor

See your eye doctor (ophthalmologist or optometrist) if your eyesight is worsening rapidly, which might be caused by an irregular curvature of the eye (astigmatism). He or she may also look for signs of keratoconus during routine eye exams.

If you’re considering laser-assisted in-situ keratomileusis (LASIK) eye surgery, your doctor will check for signs of keratoconus before you proceed.

 Diagnosis:

Keratoconus requires a diagnosis from a competent eye doctor who is trained in not only recognizing the symptoms but also observing signs of keratoconus through direct measurement as well as inspection of the cornea at a microscopic level using a slit lamp. 

To diagnose keratoconus, your eye doctor will review your medical and family history and conduct an eye exam. Tests to diagnose keratoconus include:

• Comprehensive Eye Exam – A thorough exam is the first step in diagnosing this condition.
• Slit-lamp examination. In this test your doctor directs a vertical beam of light on the surface of your eye and uses a low-powered microscope to view your eye. He or she evaluates the shape of your cornea and looks for other potential problems in your eye. The classic signs of keratoconus that the doctor will see when examining your eyes include:

1. Corneal thinning
2. Fleischer’s ring (an iron coloured ring surrounding the cone)
3. Vogt’s striae (stress lines caused by corneal thinning)
4. Apical scarring (scarring at the apex of the cone) 

The doctor may repeat the test after you’ve had eyedrops applied to dilate your pupils. This helps with viewing the back of your eye.

• Keratometry. In this test your eye doctor uses Keratometry to focus a circle of light on your cornea and measures the reflection to determine the basic shape of your cornea. The shape of the reflection of the pattern tells the doctor how the eye is curved.

Computerized corneal mapping. 

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. Corneal topography, a computerized instrument that make three-dimensional “maps” of the cornea.  The tests can also measure the thickness of your cornea.

A typical corneal topography map looks like this:

Corneal topography has facilitated the diagnosis of keratoconus, helping establish the diagnosis earlier, follow progression more accurately and differentiate keratoconus from other conditions.

Treatment Options Overview

Treatment for keratoconus depends on the severity of your condition and how quickly the condition is progressing.

Mild to moderate keratoconus can be treated with eyeglasses or contact lenses. For most people, the cornea will become stable after a few years. If you have this type, you likely won’t experience severe vision problems or require further treatment.

In some people with keratoconus, the cornea becomes scarred or wearing contact lenses becomes difficult. In these cases, surgery might be necessary. The treatment options can be broadly divided into:

Eye Glasses

1. Contact Lenses
2. Thick Soft Lenses
3. RGP Lenses
4. Piggyback Lenses
5. Hybrid Lenses
6. Scleral Lenses

Surgery

1. Corneal Inserts
2. Corneal Crosslinking
3. Corneal Transplants

A. Eyeglasses or regular soft contact lenses. 

Glasses or soft contact lenses can correct blurry or distorted vision in early keratoconus. But people frequently need to change their prescription for eyeglasses or contacts as the shape of their corneas change.

The role of soft lenses in keratoconus is limited because the soft lens drapes over the irregular corneal surface and the front surface of the lens assumes the same irregular surface as the cornea without trapping a fluid reservoir so the effective refracting surface is no improvement over the original corneal surface

B. Contact Lenses

Keratoconus is managed by many different contact lens designs. There is no one design that is best for every type or 

stage of keratoconus. The needs of each individual are carefully weighed to find the lens that offers the best

 combination of visual acuity, comfort and corneal health.  

Contact Lenses For KC

Thick Soft Lenses

There are some specially designed thicker soft lenses retain more of a rigid shape and may contribute to the liquid lens effect to some extent. There are designs being used for keratoconus, and they are helpful in mild to moderate cases.

RGP (Hard) Contact Lenses

Rigid Gas Permeable (RGP or GP) contact lenses are often the next step in treating progressing keratoconus. Hard lenses may feel uncomfortable at first, but many people adjust to wearing them and they can provide excellent vision. This type of lens can be made to fit your corneas. The rigid lens masks the underlying irregular cornea and functions as the new refractive surface of the eye, with the tear film filling in the space between the back of the contact lens and the front of the eye. “Rigid” defines the type of lens. “Gas Permeable” describes the lens material. There are many different RGP lens designs.

Piggy-backs Lenses

If rigid lenses are uncomfortable, your doctor may recommend “piggybacking” a hard contact lens on top of a soft one. This is a two-lens system: an RGP lens worn on top of a soft lens. The RGP lens provides crisp vision and the soft lens acts as a cushion providing comfort.

Hybrid lenses

This is a lens design combination that has an RGP centre surrounded by a soft peripheral “skirt”. Hybrid contact can provide the crisp optics of a RGP lens and wearing comfort of soft contact lenses. They are available in a wide variety of parameters to provide a fit that conforms well to the irregular shape of a keratoconus eye.

Scleral lenses

These are large diameter lenses that rest on the white part of the eye, called the sclera, and vaults over the cornea. The size can be an alarming prospect for some, but scleral lenses have many advantages. Because of their size, they do not fall out and dust or dirt particles cannot get under them during wear. They are surprisingly comfortable to wear because the edges of the lens rests above and below the eye lid margins so there is no lens awareness. The introduction of rigid gas permeable (RGP) materials has made this design more readily available.

There is no one “best” lens for keratoconus. The “best lens” is the one that fits your eye, corrects your vision and is comfortable to wear. Rely on an experienced KC lens fitter to select the best for you, but there is no reason why you should not input into the discussion. Contact lens fitting for keratoconus is part science and part art. A great deal of patience is required both on the part of the fitter and the patient. You’ll also need to have regular check-ups to determine whether the fitting remains satisfactory. An ill-fitting lens can damage your cornea.

Abnormal Symptom

It is important to call your contact lens fitter immediately if you should experience any of the following abnormal symptoms:

• Pain: when placing lenses on the eyes, while wearing the lenses, or after removing them
• Burning, a sensation of heat, redness, excessive tearing, or discharge
• Inability to keep the eyes open
• Extreme sensitivity to light
• Severe or persistent haze, fog, or rainbows around lights
• Severe irritation
• White spots on the cornea

By complying with the recommended care regimen, recognizing the early signs and symptoms of adverse reactions, and seeking professional care immediately if any complications do arise, patients with keratoconus should be able to look forward to many years of successful contact lens wear. Just a few minutes of lens care each night can ensure a lifetime of success.

Rigid Contact Lenses: Do’s and Don’ts

There are a number of things you should be aware of for the successful care of your rigid lenses.  Here is a list of some do’s and don’ts that should help you avoid any unnecessary complications:

• Clean your lenses at night, immediately after you remove them from your eyes. Leaving them in the soaking solution without cleaning until morning reduces the effectiveness of the disinfecting chemicals. In addition, rinsing the cleaner off with tap water just prior to replacing the lenses in your eyes might introduce bacteria or other microorganisms that would ordinarily have been killed while the lenses soaked overnight.
• If your lenses ever dry out, soak them for at least 4 hours before you wear them again, since they may have warped or flattened in curvature when the liquid evaporated.
• Do not mix and match solutions made by different manufacturers. Doing so may cloud your lenses, cause them to become gummy, or irritate your eyes. Make sure that the cleaning, soaking, disinfecting, and wetting/rewetting products you buy are all part of the same care system.
• Always store your lenses in a case with ridges on the bottom. Lenses tend to suction onto smooth-bottomed cases and may chip if you try to pry them up at the edges.
• Replace your case each time you buy a new bottle of wetting/soaking or cleaning/soaking solution. Cases tend to become contaminated. You can clean case with your contact lens cleaner using a brand-new inexpensive toothbrush. Be sure to rinse the case well before using it again.
• If the skin on your hands is rough, ask your contact lens fitter if you can use a manually-agitated device such as the Allergan Hydramat or a mechanical device such as the Clensatron. These devices work like miniature washing machines and may protect the lenses from becoming scratched from your rough skin.
• If you remove your lenses with a suction cup make sure you know exactly where the lens is before placing the suction cup on the eye. Suction cups should be cleaned with contact lens cleaner and rinsed after each use. They can also be soaked in wetting/soaking or cleaning/soaking solution.
• If you drop a lens, do not drag it along a surface. Wet your finger with wetting/soaking or rewetting solution and touch it gently to the lens to lift it

C. Surgery

You may need surgery if you have corneal scarring, extreme thinning of your cornea, poor vision with the strongest prescription lenses or an inability to wear any type of contact lenses. Several surgeries are available, depending on the location of the bulging cone and the severity of your condition.

Surgical options include:

Corneal Inserts

Intacs is the trademark name for micro-thin prescription inserts which were previously used as a form of refractive surgery in the treatment of low levels of myopia or near-sightedness, but has recently received FDA approval for keratoconus.

Inserts are thin plastic, semi-circular rings inserted into the mid layer of the cornea. When inserted in the keratoconus cornea they flatten the cornea, changing the shape and location of the cone. The placement of Inserts remodels and reinforces the cornea, eliminating some or all of the irregularities caused by keratoconus in order to provide improved vision. This can improve uncorrected vision, however, depending on the severity of the KC, glasses or contact lenses may still be needed for functional vision.

The Procedure

This procedure involves placing the plastic inserts just beneath the surface of the eye in the periphery of the cornea. The procedure itself takes approximately 15 to 20 minutes. Topical anesthetic drops are used to numb the eye, and a clamp is used to hold the eye open throughout the procedure to prevent blinking. There are 3 basic steps to the procedure:

Step 1: A single, small incision is made in the surface of the cornea. Instead of using mechanical cutting, some surgeons may use a laser to make the incision.

Step 2: A centring guide is placed on the surface of the eye for several minutes to help stabilize the eye and ensure proper alignment of the Intacs insert. During this time, the corneal layers are gently separated in a narrow circular band on the outer edge where the Intacs will be placed.

Step 3: The Intacs inserts are placed. Once this insertion is completed, the small opening in the cornea is closed with a suture.

Follow-up visits will be required to monitor the healing process and to evaluate the visual benefits of the procedure. Even after a successful procedure, glasses or contacts may be required.

As with any surgical procedure, there are some risks, including infection. Some patients experience visual symptoms including difficulty with night vision, glare, halos, blurry and fluctuating vision.

Crosslinking

Corneal Collagen Crosslinking with Riboflavin (CXL) is a developing keratoconus treatment.  CXL works by

 increasing collagen crosslinks which are the natural ‘anchors’ within the cornea. These anchors are responsible for preventing the cornea from bulging out and becoming steep and irregular.

Corneal Collagen Cross-Linking

A new minimally invasive procedure called Corneal Collagen Cross-linking with Riboflavin (C3-R®) has now been developed. Cross Linking of Cornea Collagen (C3R) increases the mechanical stability of corneal tissue. The aim of this treatment is to create additional chemical bonds inside the corneal stroma by means of a highly localized photo polymerization. This treatment uses a combination of Riboflavin drops and ultra violet light that react with the tissues in the cornea, strengthening them by creating more ‘cross-linking’ among them. The resulting increased stiffness and rigidity of the cornea stabilises ectasia. Patients who previously had progressive ectasia have now been treated and followed for up to five years without evidence of any further change in their condition.

Collagen crosslinking is not a cure for keratoconus. The aim of this treatment is to arrest progression of keratoconus, and thereby prevent further deterioration in vision and the need for corneal transplantation. Glasses or contact lenses will still be needed following the cross-linking treatment (although a change in the prescription may be required) but it is hoped that it could limit further deterioration of vision. 

The Device for C3R
For C3R we need riboflavin dye and a special device called cross-linker. Cross linker is a device to deliver UV-A light of specific wavelength of 365 nm, at controlled energy level of 3 mW/cm.sq.

The C3R Procedure
After removal of the corneal epithelium, riboflavin solution is instilled for 30 minutes on to the cornea. Then the corneal penetration of this is checked by establishing that the anterior chamber is slightly yellow. Pachymetry is performed to make sure that minimum corneal thickness is maintained.

UV-A radiation starts under continued administration of Riboflavin Solution. After 30 minutes of radiation treatment is finished and the patient receives post-operative treatment like after a PRK procedure. A bandage contact lens is inserted in the operated eye and the patient is administered oral and topical antibiotics, steroids, anti-inflammatory medication as well as lubricant eye drops. 

During the follow up assessments of eyes treated with collagen cross-linking, very few patients showed further progression. In approximately 80% of the patients a regression of the maximal K-values (regression of the keratoconus) has been observed. Post-surgical corrected visual acuity improvement of 1 to 2 Snellen lines can be expected. No unwanted side effects such as opacification of the lens or loss of endothelial cells has been reported.

Only during the first 2 to 3 months after the cross-linking has a minor superficial corneal haze been observed. Generally, this minor haze disappears without any treatment, but a supportive therapy with soothing ointment or with local steroid drops (i.e. FML or Prednisone) can be prescribed under supervision.

Lifetime Aftercare

Due to the progressive nature of keratoconus, lifetime monitoring and care is essential.

The corneal surface and biomechanical properties are first surgically stabilised using a combination of advanced Topography Guided Laser treatment combined with Riboflavin Corneal Collagen Cross-linking. The resultant topography (profile) is relatively normalised and more symmetric. Hence post-operative contact lens fitting with improved tolerance becomes a viable option. The focus when fitting a keratoconic eye with a contact lens is on stable visual acuity with minimum long-term corneal stress and influence.

Corneal Transplants

Although only 15-20% of those with keratoconus ultimately require corneal transplant surgery, for those who do, it is a crucial and sometimes frightening decision. 

 In keratoconus, a corneal transplant is warranted when the cornea becomes dangerously thin or when sufficient visual acuity to meet the individual’s needs can no longer be achieved by contact lenses due to steepening of the cornea, scaring or lens intolerance. Lens intolerance occurs when the steepened, irregular cornea can no longer be fitted with a contact lens, or the patient cannot tolerate the lens.

If you have corneal scarring or extreme thinning, you’ll likely need a cornea transplant (keratoplasty).

Lamellar keratoplasty is a partial-thickness transplant, in which only a section of the cornea’s surface is replaced.

Penetrating keratoplasty is a full-cornea transplant. In this procedure, doctors remove a full-thickness portion of your central cornea and replace it with donor tissue.

A deep anterior lamellar keratoplasty (DALK) preserves the inside lining of the cornea (endothelium). It helps avoid rejection of this critical inside lining that can occur with a full-thickness transplant.

Recovery after keratoplasty can take up to few weeks, and you may need to continue wearing rigid contact lenses to have clear vision. Full improvement of vision may occur few months after your transplant.

Cornea transplant for keratoconus generally is very successful, but possible complications include graft rejection, poor vision, astigmatism, inability to wear contact lenses and infection.