What is Keratoconus?
Keratoconus is a progressive disease of the cornea shape and generally affects both eyes (usually one more than the other). The underlying problem is weakness of the supporting collagen fibres of the cornea. This makes the cornea structurally and biomechanically “weak”. As a result, the cornea assumes a more conical shape with resultant irregular astigmatism or what is defined as an “irregular rugby ball shape”.
Keratoconus is a common disease and its incidence has been estimated for the age 10-44 at 1/1750 in white European and 1/440 in Asians.
Keratoconus symptoms include substantial distortion of vision (caused by the irregular high astigmatism), with multiple images, blurry vision and sensitivity to light (photophobia). Initially, most people can correct their vision with glasses, but as the astigmatism progressively gets worse patients may need to be managed with specially fitted rigid contact lenses to reduce the distortion and provide better vision. In the vast majority of the younger patients, the condition is progressive and requires intervention.
The cornea is the main optical lens of the eye. The cornea helps focus images onto your retina at the back of the eye. As the cornea begins to bulge in keratoconus patients, the regular optics of the cornea are distorted and it therefore becomes difficult to focus a clear image onto the retina. This can result in distortion, ghosting and multiple image formation. As keratoconus progresses, it is more difficult for spectacles to correct vision. Most keratoconus patients achieve their best vision with a rigid contact lens which works by arching over the bulging cone of cornea and creating a new artificial smooth spherical surface.
Other KC symptoms may include:
- Blurred or hazy vision
- Double vision
- Poor vision in bright light
- Seeing halos around lights
- Poor vision at night
- Yellowish tinged vision
Keratoconus tends to begin during teenage years and continues to progress up to the late 30’s, after which it tends to slow down and it then usually remains stable. In youth, the cornea is more elastic and has a layered structure. These layers can become stretched due to genetic characteristics, pressure within the eye or most importantly: eye rubbing. Eye rubbing must be avoided in KC at any costs since it is the main cause of KC progression nd worsening. The progression of Keratoconus can be quite variable, but the rule is: the younger the patient, the more the progression. A genetic predisposition to keratoconus has been observed, with the disease running within families in more than 20% of all cases. Unfortunately, if the condition isn’t treated early with corneal collagen cross linking (CXL), patients are left with an abnormal shaped cornea that requires a contact lens to see well or corneal graft transplant surgery. Keratoconus is a very variable disease and can be mild in one person and not progress very much, whilst being severe and rapidly progressive in other cases.
The diagnosis of Keratoconus is based on the patient’s history and a complete ophthalmological examination including sophisticated corneal imaging such as the pentacam corneal three-dimensional scanning tomography that allows to confirm the diagnosis and to grade the keratoconus. The pentacam corneal imaging is also used to check for KC progression with serial scans comparisons. The pentacam – click her to find more about the pentacam- is the industry standard device for measuring the corneal shape accurately in three dimensions. At your consultation, pentacam imaging scans will help us determine the most appropriate initial treatment. Subsequently, pentacam scanning will be used to ensure that your corneal shape is stable by comparing scans between visits. Please bring a USB flash drive so that we can give you your pentacam image files to keep. For accurate scans, you should not use rigid contact lenses for two weeks prior to review visits.
In the past, just two decades ago, there were no treatments available to stop keratoconus getting worse. Patients were given rigid contact lenses once spectacles were no longer effective, and corneal transplantation when contact lenses were no longer tolerated. The two fundamental aims in modern keratoconus treatment are: 1. stopping progression (so called shape stabilisation) and 2. restoring good vision. Corneal Collagen Cross-linking (CXL) has emerged as a safe and effective method to halt keratoconus progression preventing further corneal shape deterioration.
How does CXL work?
The human cornea consists of a number of layers responsible for its strength. These layers are made of millions of collagen fibres in close contact with each other. Cross-linking is a surgical procedure that combines the use of Ultra-Violet light and Riboflavin eye drops. During cross-linking vitamin B2 drops (Riboflavin) are applied to the cornea and then the cornea is exposed to ultra-violet light. The UV light catalyses a chemical reaction which leads to the formation of bonds between collagen molecules named collagen cross-linking.
The Avedro KXL Accelerated Cross-linking pulsed procedure is the most advanced collagen cross-linking and it is performed in 15-18 minutes, while older techniques typically take longer than 30 minutes. Ultraviolet (UVA) light in the presence of vitamin B2 (riboflavin B) induces free radical formation inside the cornea and this causes collagen cross linking. CXL treatment therefore aims to create increased corneal strength and stiffness.
The ophthalmology community has fully accepted the prominence of corneal collagen cross-linking as a treatment strategy for progressive keratoconus and post-LASIK ectasia. A rapidly growing number of clinical reports suggest a consistent stabilizing effect of cross-linking along with a variable improvement in corneal shape and visual function in some patients. As a first-line treatment, the aim of cross-linking is to reduce and stop keratoconus progression in the early phase of the condition, and as a consequence, this will prevent the progressive vision loss that occurs in time and leads to the need for corneal transplantation.
Learn more about CXL Treatment
NICE is the national agency that evaluates medical technologies and treatments to ensure that they are safe for patients. Corneal collagen cross-linking was first developed in the late 1990’s and is now widely used as a treatment for keratoconus.
Read the latest NICE guidelines for cross-linking.
Vincenzo Maurino has been performing CXL for 10 years and has a wealth of experience in conferral surgery for keratoconus in general. We use the cutting edge high fluence pulsed Avedro Collagen Crosslinking, which makes the treatment last only minutes in each eye. As a result, the surgery passes quickly and the patient experience is more pleasant. Based on NICE guidelines, we mainly perform treatment after removal of the epithelium (the first layer of the cornea) since it works better although has a slower visual recovery and it is more painful after surgery for a few days . Currently very little evidence proves that epithelium on procedures are as effective. Instead, we can use the Excimer Laser Photo Therapeutic Keratectomy (PTK) to remove the epithelium in selected patients with early keratoconus in order to try to improve the vision by mild flattening the cornea. This is done only when we believe that this may lead to better post-operative vision.
For the last decade, Corneal Collagen Cross-linking (CXL) has emerged as a safe and effective method for halting further corneal shape deterioration in keratoconus. In few selected cases an excimer laser guided by the abnormal corneal shape (COMA) can be used to try to improve vision as well as stabilising the corneal shape. Only few patients can benefit from this technique and at your consultation we will explain if this is possible for you
Corneal Collagen Cross-linking (CXL) and Epithelial PTK removal
Some keratoconus patients do see improvement in their vision after cross-linking due to overall flattening of the cornea and secondary reduction in astigmatism. By using the Excimer Laser in PTK (Photo Therapeutic Keratectomy) mode to remove the epithelial layer before performing cross linking it is possible to preferentially flatten the bulging part of the cornea, thereby causing a greater flattening of the steeper areas of the keratoconic cornea and reducing the astigmatism after the cross-linking procedure. This might lead to a better correction of vision. It is not possible to do this by simply scraping the epithelium away that is the common practice.
Corneal Collagen Cross-linking (CXL) and wavefront or topographic guided Trans-PRK
More recently, other treatments for shape correction and visual rehabilitation have been developed in the attempt to improve vision in keratoconic patients. Those advanced treatments consist in performing Corneal Collagen Cross-linking (CXL) together with gross corneal re-shaping using topographic (corneal anterior elevation) or wavefront (ocular aberration) guided Excimer laser Photo Therapeutic Keratectomy (PTK) ablation or No Touch Trans epithelial Excimer Laser Photo Keratectomy (Trans-PRK).
The emphasis in keratoconus treatment has now moved onto a much more positive approach directed at seizing the disease progression and restoring good unaided vision.
Mr Maurino will be able to discuss all available treatment in details and choose the best and most customised treatment for your keratoconus.
The patient lies back on an operating table and local anaesthetic eye drops are applied. The surgeon then removes the superficial protective outer layer of the cornea (the epithelium) with a specially designed instrument or the using an excimer laser in PTK mode (see above). Riboflavin eye drops are then applied until the cornea turns fully yellow for about 10 minutes. Special UVA light is then focused precisely and applied to the cornea for about 8 minutes (pulsed Avedro). This process encourages the formation of free radicals in the cornea, resulting in collagen cross-linking. Treatment is completely painless. At the end of the procedure a bandage contact lens is applied to the eye. Once the procedure is finished and Mr Maurino has checked your eyes, you will be free to return home.
The bandage contact lens stays in place for 5-7 days and is removed at the planned follow-up appointment after surgery. After the procedure you will be discharged with antibiotic and anti-inflammatory drops that you will use for a few weeks. An appointment is always scheduled 5-7 days after surgery to ensure proper healing and remove the bandage contact lens. After, you will be followed-up every six months with repeated ophthalmological assessment including serial pentacam three-dimensional corneal tomography imaging to check the keratoconus is stable
As with all eye surgeries, some risks do exist. The application of UVA light and the induction of free radicals within the cornea can cause damage to the surrounding area of the eye. The UVA light is absorbed by the riboflavin on the cornea to a depth of around 300 microns (0.3mm). The cells within this area (keratocytes) are destroyed, taking an average of six months to regenerate. The intensity of the UVA light is fully controlled using a medical device with an appropriate CE marking.
Corneal thickness is measured before surgery; a minimum thickness of 350-400 (0.35-0.4mm) microns is required. However, it is been possible to treat patients with thinner corneas using specially produced riboflavin eye drops and special techniques.
Read the latest NICE advice for cross-linking.
It is believed that the collagen in the cornea replaces itself every 3-10 years, and therefore repeat treatments may be necessary in the future. Please note the following:
- CXL is intended to stop progression in keratoconus and corneal ectasia.
- Treatment may also reduce corneal curvature as the cornea stabilises.
- Sharpness of vision may not improve.
- Long-term follow-up is required to monitor progression and corneal curvature.
- CXL may need to be repeated and other treatments, such as corneal transplant, may become necessary.
- CXL does not work in 100% of cases.
The vast majority of CXL procedures are completely uneventfully but, as with any surgery, complications may occur, which include (but are not limited to) the following.
- Corneal endothelial cell damage. This is why the cornea should be thicker than 350-400 microns for surgery or else special techniques should be used to minimize the risk.
- Corneal melting severe enough to require transplant has been reported.
- Corneal Infection can be associated with any eye surgery and, if severe, can badly damage the eyesight. The risk of infection with the CXL procedure should be similar to that of laser vision correction surgery.
- Pain and discomfort are common in the first few days as the epithelium heals. The bandage contact lens and anti-inflammatory drops help to minimise this.
- Glare is usually temporary and may last for a few months after surgery.
- Rigidity of the cornea may not be enough to stop ectasia progression, despite treatment.
- Dry eye may occur – this may be eased by use of artificial tear drops for several months.
- Corneal vascularisation (blood vessel growing into the cornea) may occur if there has been melting or infection.
- Cataract formation. At present there is no evidence that the UVA light used during CXL can cause cataract formation.
- DLK (Diffuse Lamellar Keratitis) is an inflammatory process of the cornea that may require treatment with steroid drops and can damage the cornea.
- Ptosis (drooping of the eyelid) can occur during any eye surgery or even when using eye drops.
- Transient light sensitivity may potentially occur.
- Serious complications may damage the eyesight and affect visual clarity, driving ability, etc.
After surgery there are no dietary or lifestyle restrictions, but you should use common sense and follow our post-operative care instructions carefully. You do not need to discontinue any medication you would normally take. Pregnancy and breastfeeding are contraindications to most eye surgeries, since the effects of treatment on pregnancy are unknown and likewise the effects of pregnancy upon the result of treatment are also unknown.
Most people choose to have both eyes treated at the same time for convenience, just as with laser vision correction eye surgery.
Please note that, whilst your records remain confidential, medical data concerning the outcome of the treatment and any subsequent treatment may be used for audit or publications, but your identity will not be disclosed. As consistent with the best practice in medicine, we audit our own outcomes regularly.
Finally, a note about epithelium on CXL, which is performed without removing the corneal epithelium, so called “EPI ON” CXL. At present there is increasing evidence showing some/part efficacy for EPI ON CXL but it is still to be fully confirmed. We have used it with success in special cases or in thinner corneas.
Why choose Mr Maurino at Moorfields?
Vincenzo Maurino has been a Consultant Eye Surgeon at Moorfields Eye Hospital with specialist expertise in cornea, lens and laser vision correction eye surgery since 2002 and has a wealth of experience in corneal diseases, particularly in the field of keratoconus. He is Visiting Professor of Corneal Surgery at the prestigious University “Tor Vergata” in Rome and has performed more than thirty thousand eye operations to date . True to his world renowned reputation, Mr Maurino’s results are second to none and he always offers the best choice of customised treatments to serve his patient at best.