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Treatment for Keratoconus
Home|Other Treatments|Keratoconus Treatment

Keratoconus Treatment

  • Keratoconus is a fairly uncommon condition that affects the cornea (the transparent window at the front of the eye).
  • Keratoconus causes changes within the structure of the cornea making it weaken and thin resulting in a 'cone shaped' forward bulge.
  • Keratoconus leads to myopia (short sight) and, if the steepening is uneven, also astigmatism (distortion of vision).
  • With Keratoconus, visual distortion can become difficult to correct with spectacles, although contact lenses (usually rigid) can provide more functional visual performance.
What is Keratoconus ?
Illustration showing effects of keratoconus

Keratoconus is a congenital disease of the cornea (autosomal dominant or autosomal recessive) and it belongs to the large group of hereditary corneal dystrophies.

The disease is characterised by thinning and conus-like protrusion of the cornea. This is due to alterations that cause weakening of the corneal structure.
 

At first, the protrusion occurs in the inferior parts (lower half) but later on it also affects the central part of the cornea. Keratoconus mostly happens to be bilateral but often the progression is asymmetrical.

Symptoms of Keratoconus
Diagram showing cross-linking structure

Keratoconus symptoms usually start during puberty or early adolescence. As the keratoconus progresses it leads to myopia (short sight) and, if the steepening of the cornea is uneven, also astigmatism (distortion of vision). In most cases patients realise a decrease or blurring in vision, or an increasing myopia with a significant progression of astigmatism. Patients usually seek corrective lenses at first for driving or reading. Keratoconus at this stage is difficult to differentiate from other more common vision defects. The incidence of keratoconus in the general population is reported to be about 1 in 2000.

 
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 hayfever, 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.

Possible Treatment For Keratoconus

There is no cure for keratoconus and treatment is therefore aimed at optical improvement. Depending on the degree of corneal bulging, (ectasia) thinning of the cornea and resultant astigmatism, a number of options can be considered:

Contact Lenses
Contact Lenses

In advancing cases of keratoconus, rigid (hard) contact lenses help to improve visual acuity, yet they cannot stop the progression of the condition.

 
Corneal Ring Segment Insert (Intacs)
Corneal Ring Segment Insert (Intacs)

Clear plastic segments are placed into the cornea (pictured left). Intacs typically only partially correct the optical defect present, so additional optical aids or surgical intervention may be required to obtain full visual correction.

 
Corneal Transplantation
Corneal Transplantation

Upto until a few years ago, the only therapeutic option for vision restoration in advanced cases of keratoconus was corneal transplantation (penetrating keratoplasty) to achieve better vision.

 
Corneal Collagen Cross-Linking
Corneal Collagen Cross-Linking

A new minimally invasive procedure called Corneal Collagen Cross-linking with Riboflavin (C3-R®) has now been developed. This treatment uses a combination of Riboflavin drops and ultra violet light that reacts 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.

 
Pre-op and post-op topography
Corneal Collagen Cross-Linking (C3R®) at Accuvision

The aim of this treatment is to stabilise the cornea and prevent the progression of keratoconus.

The main structure of the corneal tissue (stroma) consists of single collagen fibres which are linked. The treatment of keratoconus with collagen cross-linking is based on a significant stiffening of the corneal stroma due to photochemical cross-linking of the single collagen fibres. Therefore the single fibres form a "denser network" which leads to an increase in the overall stability of the cornea. This procedure is performed under topical anaesthesia.

After an epithelium abrasion (corneal scraping), Riboflavin (vitamin B) drops are applied to the corneal surface over a period of 30 minutes and the cornea is then exposed to 365nm UV for a 30 minute period thereafter.

After the treatment a bandage contact lens is applied and a combination of a steroid and antibiotic drop is prescribed. 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.

 
Pre-op and post-op 3D topography
Accuwave™ Topography Guided Custom Ablation Treatment for Keratoconus (T-CAT)

In addition to 'simple' cross-linking, Accuvision can offer selected patients combined corneal collagen crosslinking with corneal laser re-shaping.

This advanced treatment is designed to improve central corneal symmetry, without attempting to correct other spherical, or regular astigmatic, optical defects.

Advanced Topography Guided (T-CAT) laser treatment is kept to a small degree of tissue ablation, with the maximum depth of tissue loss typically less than 50 microns. Corneal Collagen Cross-linking with Riboflavin (C3-R®) treatment is applied immediately after the laser treatment. Any spherical or regular astigmatic, optical defect remaining after the combined Accuwave™ T-CAT treatment with Corneal Collagen Cross-linking can be corrected subsequently by contact lens wear or by phakic intra-ocular lens implantation.

 

C3-R® - Keratoconus Treatment

Potential Risks of C3-R Treatment for Keratoconus

Keratoconus can be treated with a relatively new procedure called Corneal Collagen Cross-linking with Riboflavin (C3-R®). This is a new treatment that increases the stiffness and rigidity of the cornea and 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. At present it is not known whether the stabilising effect of C3-R® on keratoconus is permanent, but the C3-R® treatment could potentially be repeated if it was necessary.

Potential Risks of C3-R Treatment for Keratoconus

How does C3-R® for Keratoconus work?

The bulk of the cornea is made from collagen fibres which are arranged in bundles. The strength and rigidity of the cornea is partly determined by how strongly the fibres are linked together. Over the course of a lifetime the cornea becomes progressively stiffer due to natural cross-linking between the fibres.

Riboflavin (vitamin B2) is a naturally occurring compound which strongly absorbs UV light. By applying riboflavin to the cornea at the same time as exposing it to a UV light source, the riboflavin not only enhances the cross-linking effect of the UV light, but also absorbs the light to an extent that the inner layers of the cornea and intra-ocular structures are protected from the potentially damaging effects of the light rays.

Benefits of C3-R® for Keratoconus

C3-R® for keratoconus seems effective in stabilising progressive ectasia, and in some patients the treatment gives an additional small measure of benefit in the reduction of corneal steepness and irregularity. This in turn means some reduction in the myopia and astigmatism associated with the ectasia.

In the past it was always considered that excimer laser eye surgery correction of myopia or astigmatism was not possible when ectasia was present. This was because by removing corneal tissue with the laser the cornea would become even less stable and the ectasia would be made worse. However, once the Keratoconus condition is stabilised by C3-R® it may be possible to perform limited amounts of laser eye surgery whilst still maintaining structural stability of the cornea. Such laser eye surgery treatment would usually be aimed at restoring a more spherical shape to the cornea (custom ablation). Any remaining optical defect could then potentially be corrected by spectacles, or alternatively with soft contact lenses, or by phakic intra-ocular lens implants.

Risks of C3-R® for Keratoconus

UV light is known to be damaging to cells, and the keratoconus treatment causes the stromal cells (keratocytes) in the outer layers of the treated parts of the cornea to die. However, these cells are replaced by new keratocytes which migrate from untreated parts of the cornea into the central area over a period of some months after the keratoconus C3-R® treatment. In theory the UV light could be damaging to the inner endothelial cell layer of the cornea, and this is why the corneal thickness needs to be at least 350 microns if a standard keratoconus C3-R® treatment is to be undertaken. In clinical studies carried out so far, no evidence of damage to the endothelial cell layer has been documented. Although UV is potentially damaging to the lens and retina, it is believed that the riboflavin blocks the UV transmission to an extent that no measurable damage will occur. At present the long term effects of the keratoconus treatment are unknown.

How is Keratoconus C3-R® treatment given?
Keratoconus C3-R Treatment

The keratoconus C3-R® treatment is carried out with topical anaesthesia (eye drops). The surface epithelial cell layer is removed from the central part of the cornea, and the riboflavin drops applied. Once the riboflavin has penetrated well into the eye, the UV light is focused onto the central area of the cornea for 30 minutes.

Finally a bandage soft contact lens is applied. The contact lens is worn for three or four days until the surface epithelial cell layer has re-grown. During the first few days the eye will be sore and watery. Sometimes there is slight haziness under the epithelial layer for the first few months after treatment, but the vision stabilizes within a month or so of the treatment.

C3-R® is a registered trademark of Boxer Wachler Vision Institute.

Results
  • All patients exhibited a reduction in irregular astigmatism
  • Mean improvement in topographical asymmetry was 7.8D
  • Two thirds of patients had improved Best Corrected Visual Acuity
  • No patients lost Best Corrected Visual Acuity
Patient Difference along steepest meridian: Gain/Loss
BCVA
(Snellen Lines)
Pre-Op Post-Op Improvement
SMR 8D 2.5D 5.5D +1
SML 13D 3D 10D =
MGR 15D 2D 13D +3
GCR 3D 1.5D 1.5D +1/2
GCL 8.5D 0.5D 8D +1
SBR 5D 3D 2D =
SBL 8D 3.5D 4.5D +1
PBR 7D 5D 2D =
PBL 13D 7D 6D +2
IOR 18D 4D 14D +1
IOL 21D 11D 10D +1/2
PJR 18D 4D 14D +4
PJL 10D 2D 8D +1
JOR 17D 6D 11D =
JOL 14.5D 2.5D 12D =
MWR 11D 6D 5D +1
LSR 6D 2D 4D =
PPR 9D 0D 9D +1
PPL 7D 3D 4D =
Intacs for Keratoconus

An alternative treatment for Keratoconus is the use of Intacs, implanted into the cornea.

Intacs for Keratoconus

Intacs are a new surgical treatment for mild to moderate keratoconus. When inserted into the cornea, the Intacs segments make the central corneal profile flatter and more regular, and this reduces the optical defect.

Intacs for keratoconus are 'C' shaped segments of perspex (polymethyl-methacrylate or PMMA), that are inserted deep into the corneal stroma. They were originally designed for treatment of low myopia, and typically correct two or three dioptres of myopia or myopic astigmatism. Patients with keratoconus often have moderate or high degrees of myopia and astigmatism due to irregular steepening of the cornea caused by the condition.

For these patients, Intacs for keratoconus will reduce the optical defect in the eye and the remaining myopia and astigmatism can then be corrected either with glasses, or by insertion of an Implantable Contact Lens (ICL), or by Artisan lens surgery.

Intacs for Keratoconus - Surgical Procedure

Insertion of Intacs can be carried out with topical, local, or general anaesthesia according to the patient's preference.

A two millimetre incision is made into the cornea to a depth of about two thirds of its thickness, and a special instrument is then used to prepare the bed into which the Intacs for keratoconus are inserted. Once they have been put into position, a single stitch is used to close the small corneal wound. Eye drops are used for a few weeks to settle the eye down, but the patient can resume normal activities more or less straight away. The corneal suture is removed after a couple of weeks with application of anaesthetic eye drops.

Advantages of Intacs for Keratoconus

Insertion of Intacs is a relatively quick and simple surgical procedure compared to the other operations for keratoconus such as epikeratoplasty, or deep anterior lamellar keratoplasty (DALK). For those who do not wish to have a corneal transplant, it offers an alternative approach for correction of their optical defect.

By making the shape of the cornea more regular, Intacs for keratoconus can potentially improve the quality of vision that can be obtained when wearing a spectacle correction.

Disadvantages of Intacs for Keratoconus

Intacs typically only partially correct the optical defect present in a patient suffering from keratoconus, so additional optical aids or surgical intervention may be required to obtain a full visual correction.

Sometimes the quality of vision obtained after Intacs surgery is not as good as that obtained before the surgery.

In keratoconus the cornea is thin, so there is some risk of corneal perforation at the time of surgery. If this happens, insertion of the Intacs would have to be abandoned on that occasion, although it may be possible to attempt the surgery again at a later date. Rarely, Intacs that have been successfully inserted may migrate through the cornea and extrude through the corneal surface, in which case they would need to be removed.

As with any surgical procedure, there is a potential for complications from infection or inflammation in the cornea, which might necessitate removal of the implants.

Because Intacs insertion is a relatively new procedure, the long term outcomes are not known.

Accuvision Lifetime Aftercare
Accuvision 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.

 

Often, there are many questions that are considered when a contact lens fit is mentioned post operatively. Some of the most common questions are addressed below:

Why can't I wear glasses instead of contact lenses?

It is possible to wear glasses, however the visual acuity can be limited. Though the corneal surface has been stabilised as much as possible, it is still relatively irregular when compared to a 'normal' eye. This means that a contact lens offers a much better quality of vision.

Why can't I wear soft contact lenses?

Soft lenses mould to the shape of the eye and therefore mirror rather than mask any irregularities in the corneal surface. A rigid lens creates a smooth surface that allows tears to flow more freely and therefore improves oxygen accessibility to the cornea. This offers the additional benefit of a healthier eye even with long term or extended wear.

I have tried hard (Rigid Gas Permeable or RGP) lenses in the past and they were uncomfortable or gave poor vision or were difficult to handle. Why would this be different now?

After treatment, the corneal surface is much more regular and therefore more responsive to a lens. This means that since the lens fit is enhanced, vision is improved and therefore patient satisfaction is much more likely. Additionally, the Accuvision Team is highly experienced and specialised in complex contact lens fits and this will ensure that patients are taught how to handle, care for and manage lenses on a personalised basis.

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