KERATOCONUS AND CORNEAL COLLAGEN CROSS-LINKING

KERATOCONUS  (cone shaped cornea)
What is keratoconus? Keratoconus is a common bilateral corneal condition, occurring in more than 1 in 1000 people. The condition typically starts in adolescence and early adulthood. Keratoconus is a disease with an uncertain cause, and its progression following diagnosis is unpredictable. If afflicting both eyes, the deterioration in vision can affect the patient's ability to drive a car or read normal print. Further progression of the disease may lead to a need for surgery. Despite its uncertainties, keratoconus can be successfully managed with a variety of clinical and surgical techniques, and often with little or no impairment to the patient's quality of life. Keratoconus (from Greek: kerato- horn, cornea; and konos cone) The cornea is the clear window on the front of the eye. It is usually a regular spherical dome in shape. The substance of the cornea consists of hundreds of layers that are linked to each other by a substance called collagen. If these collagen cross-links between layers are lost due to keratoconus, there is a progressive corneal thinning and stretching which gradually progresses, often in both eyes. Normal pressure within the eye causes the cornea to bulge forward into an irregular cone shape. When light enters the eye, it first passes through the cornea. If the cornea has turned conical, there is distortion of the image. The eye develops astigmatism (cylindrical errors) and myopia [shortsightedness] and the vision may become severely blurred.
A simulation of the multiple images seen by a person with keratoconus
RISK FACTORS Reported risk factors for keratoconus include eye rubbing, a family history of keratoconus, genetic predisposition, certain systemic disorders such as Down’s syndrome, ocular allergy, connective tissue disease, and long-term rigid contact lens wear. It is usually an inherited corneal disorder, often in an autosomal dominant fashion. This means that approximately 50% of family members may end up with it. But it also can be random with no other family members affected. It affects men and women in equal proportions and is bilateral in 90% of patients. SYMPTOMS At early stages, the symptoms of keratoconus may be no different from just having the need for spectacle correction. As the disease progresses, the vision deteriorates. Visual acuity becomes impaired at all distances, and night vision is sometimes quite poor. Some individuals have vision in one eye that is markedly worse than that in the other eye. Some develop photophobia (sensitivity to bright light), eye strain from squinting in order to read, or itching in the eye. There is usually little or no sensation of pain. Keratoconus can cause substantial distortion of vision, with multiple images, streaking and sensitivity to light. DIAGNOSIS This is usually done by an ophthalmologist with a detailed eye examination. Diagnosing early keratoconus can be tricky, since mild disease often does not show any identifiable signs on slit-lamp examination; however, recent and a more definitive diagnosis can be obtained using corneal topography, in which an automated instrument projects an illuminated pattern onto the cornea and determines its shape from analysis of a digital image. The topographical map reveals distortions or scarring in the cornea, with keratoconus revealed by a characteristic steepness of curvature which is usually below or around the centre of the cornea. The topography record of the degree and extent of the deformation is used for assessing its rate of progression. Unilateral cases tend to be uncommon. Sometimes it’s a mild condition in the better eye, below the limit of clinical detection. It is common for keratoconus to be diagnosed first in one eye and not until later in the other. At our hospital, we use a very sensitive Topography instrument called the ‘Topolyser’ from Wavelight Inc. PROGRESS However good the vision may be with the use of contact lenses, vision may be difficult to maintain at times as the condition progresses and contact lens tolerance varies. Contact lenses are used as temporary measures of treatment, but do not, unfortunately, slow down the rate of progression of the cone. In about 10% to 20% of keratoconus patients the cornea may become extremely steep, thin and irregular or the vision cannot be improved sufficiently with contact lenses. The cornea may then need to be replaced surgically with a corneal transplant or graft. Visual recovery after a transplant takes a long time - sometimes as long as a year to 18 months - to settle down and there is a strong possibility that the eye will still need to be fitted with a contact lens afterwards in order to see properly. Surgery is therefore not a shortcut to perfect vision and nor is it a way of avoiding contact lens wear. There is also a risk of the transplant rejecting afterwards, although a majority of corneal transplants done for keratoconus are successful. TREATMENT Treatment of mild keratoconus is geared towards eliminating or reducing the myopia and astigmatism. Temporary: Contact Lenses Permanent: New modality of treatment: Corneal Collagen Crosslinking with Riboflavin (C3-R®*) Contact lenses Initial management is tried with rigid contact lenses by our contact lens specialist. In very early stages of keratoconus, spectacles can suffice to correct minor astigmatism. As the condition progresses, spectacles may no longer provide the patient with a satisfactory degree of visual acuity, and most doctors will move to managing the condition with contact lenses. Rigid gas permeable contact lenses for keratoconus improve vision by means of tear fluid filling the gap between the irregular corneal surface and the smooth regular inner surface of the contact lens, thereby creating the effect of a smoother cornea. Many specialized types of contact lenses have been developed for keratoconus, and our contact lens expert helps you with the best fit. The irregular cone needs expertise to produce a contact lens with optimal contact, stability and steepness. Some trial-and-error fitting might be necessary. Traditionally, contact lenses for keratoconus have been the 'hard' or rigid gas-permeable variety, although manufacturers have also produced specialized 'soft' or hydrophilic contact lenses. A soft contact lens has a tendency to conform to the conical shape of the cornea, thus diminishing its effect. These do not however prove effective for every patient. Some patients also find good vision correction and comfort with a "piggyback" contact lens combination, in which gas permeable rigid contact lenses are worn over soft contact lenses, providing clarity of vision and comfort. Precaution with contact lenses: There is a small risk of infection when wearing contact lenses and the risk becomes much greater if the contact lenses are not kept clean, so it is important to strictly follow the hygiene instructions given when the contact lenses are fitted.
A NEW PERMANENT NON SURGICAL TREATMENT: CORNEAL COLLAGEN CROSSLINKING WITH RIBOFLAVIN (C3-R®*) So far there has been not one successful way to stop the progression of keratoconus. With current methods using rigid contact lens or intra corneal ring segments, only the refractive error (spectacle numbers) can be corrected, but it has very little effect on the progression of keratoconus. It is estimated that eventually 21% of the keratoconus patients require surgical intervention to restore corneal anatomy and eyesight. A new non surgical, non invasive treatment, based on collagen cross linking with Ultraviolet A (UVA, 365nm) and riboflavin (Vitamin B 2), a photosensitizing agent is now available. This changes the intrinsic biomechanical properties of the cornea, increasing its strength by almost 300%. This increase in corneal strength has shown to arrest the progression of keratoconus in numerous studies all over the world. What is collagen cross-linking? A new treatment for keratoconus which has shown great success is Corneal Collagen Crosslinking with Riboflavin (C3-R®*), a one-time application of riboflavin eye drops to the eye. The riboflavin, when activated by approximately 30 minutes illumination with UV-A light, augments the collagen cross-links within the stroma and so recovers some of the cornea's mechanical strength. C3-R®*, developed at the Technische Universität Dresden, Germany has been shown to slow or arrest the progression of keratoconus, and in some cases even reverse it, particularly when applied in combination with intracorneal ring segments. How is the treatment done? The treatment is performed in our operation theatre under complete sterile conditions. Usually, only one eye is treated in one sitting. The treatment is performed under topical anesthesia (using anesthetic eye drops). The surface of the eye (cornea) is treated with application of Riboflavin eye drops for 30 minutes. The eye is then exposed to UVA light for 30 minutes. Hence, the treatment takes about an hour per eye. After the treatment, antibiotic eye drops are applied; a bandage contact lens may be applied, which will be removed by our doctor during the follow up visit. Protective eye wear, such as sunglasses (also given by us) is to be worn for a few days until complete healing takes place. Who can benefit from this treatment? Collagen cross-linking treatment is not a cure for keratoconus, rather, it aims to slow or even halt the progression of the condition. This is important to understand. Patients may need to continue to wear spectacles or contact lenses (although a change in the prescription may be required) following the cross-linking treatment but it is hoped that it could limit further deterioration in the patient's vision and reduce the case for keratoplasty.The main aim of this treatment is to arrest progression of keratoconus, and thereby prevent further deterioration in vision and the need for corneal transplantation. What are the risks and consequences involved? Very few potential risks associated with this treatment have been reported so far. The Ultraviolet light dose used is designed to prevent damage to the cells that line the back of the cornea or the other structures within the eye. No lens opacities (cataracts) have been attributed to this treatment in European trials. The treatment involves the outer layer (epithelium) of the cornea. There is therefore discomfort and a short-term haze.  Other lesser but more common risks include: Inability to wear contact lenses for several weeks after the treatment Changes in corneal shape necessitates fitting of a contact lens or a occasional change in spectacle correction. As is the case with any treatment, there may also be long-term risks that have not yet been identified.  The increased corneal rigidity induced may wear off over time and further periodic treatments may be required. How does Cross Linking arrest keratoconus? Until recently, there was no method to change the integrity and strength of the cornea itself for keratoconus patients. The non-invasive treatment C3-R®* (corneal collagen cross-linking riboflavin) treatment has been proven to strengthen the weak corneal structure in keratoconus. This method works by increasing collagen cross-linking, which are the natural "anchors" within the cornea. These anchors are responsible for preventing the cornea from bulging out and becoming steep and irregular (which is the cause of keratoconus).
The figures above show the parallel corneal layers (white) and the collagen cross-linking (red) which increased after C3-R®* treatment.
Are there any published studies for the same? In published European studies, such treatments are proven safe and effective in patients. The 3 and 5 year results of Dresden clinical study in human eyes has shown arrest of progression of keratoconus in all treated eyes.  (Wollensak G. Crosslinking treatment of progressive keratoconus: New Hope. Current Opinion in Ophthalmology 2006; 17: 356 – 360). Biomechanical measurements have shown an impressive increase in corneal rigidity of over 300% after crosslinking.  The Dresden, Germany clinical study has shown that in all treated eyes the progression of keratoconus was stopped ('freezing'). In over 53% of those eyes there was a slight reversal and flattening of the keratoconus by up to 2.87 diopters. Best corrected vision improved by 1.4 lines. This technique has shown great promise in treating early cases of the disease. ADVANTAGES OF CROSS LINKING Permanent Simple- Single- one hour treatment No follow up sittings required No need for admission Stops the progress and causes regression of disease Does not need eye donation as in corneal transplant No major precautions No injections or stitches No incisions as in Intacs or Corneal ring segments Quick recovery with short follow up
Talk to our Keratoconus specialist today. A new world of natural vision could be waiting for you.
Issued in public interest by ShroffEyeHospital, Mumbai, India India’s first LASIK Centre to launch the 400 Hz Wavelight laser India’s first EyeHospital to be awarded the JCI- Joint Commission International certification (USA), the Gold standard of Healthcare Internationally. Open your eyes…to a whole new world Shroff Eye Hospital, 222 S V Rd, Bandra West, Mumbai –400 050 Ph: 66921000/ 66939372/26431006 LASIK Helpline: 98211-63901 www.lasikindia.in
* C3-R® is a registered trademark of Boxer Wachler Vision Institute