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About keratoconus
Normal Cornea
keratoconus Cornea
Keratoconus is an eye condition affecting the cornea (the front surface) of the eye. It results in an irregular cornea causing distorted (blurred) vision. Generally, keratoconus develops in the teenage years but may begin before the age of ten or not until adulthood. The word keratoconus is derived from Latin words: kerato- meaning "cornea" and -conus meaning "cone-shaped." This describes the normally round-shaped cornea becoming cone-shaped as the condition progresses. The keratoconic cornea also tends to thin with progression. Generally, keratoconus is a painless condition, although it can cause ocular irritation in more advanced cases.
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The severity of keratoconus varies widely between individuals; some may manage with spectacles alone, others may require special contact lenses, and a small minority go on to require surgery. Although keratoconus is considered a progressive condition (one that worsens over time), it is common for keratoconus to eventually stabilize (often around the age of 30).
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Keratoconus is considered to be a genetic condition, and it is common to find more than one family member or relative with the condition. Estimates vary, but the prevalence of keratoconus in NZ is approximately 1 in 2000, with 60% of keratoconics being male. Maori and Pacific Island communities appear to have a slightly higher than average prevalence.
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Conditions such as allergy (hayfever), eczema, and asthma are common in people with keratoconus. Eye rubbing due to ocular allergy is very common in keratoconus and should be avoided, as it can cause the condition to deteriorate more rapidly. Medications can be prescribed by an eyecare professional to reduce the itching caused by ocular allergy.
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How It Works
Despite growing awareness, keratoconus is often misdiagnosed, especially in mild cases. Advanced technology and practitioner experience are essential in detecting keratoconus early. Those with a family history, particularly children of patients, should undergo regular testing, as they are at higher risk.
Corneal topography, or corneal mapping, uses a computerized instrument to capture images of the corneal surface and create a detailed map. This map highlights the irregular peaks and valleys of the cornea, making it an invaluable tool for early keratoconus diagnosis and ongoing management.
The topographical image represents a typical keratoconic map. It is easy to see the asymmetrical pattern with the red area representing the protruding area the cornea below the centre.
The map represents a non-keratoconic cornea. Note the symetrical pattern centred aroung the middle of the cornea.
This map represents regular astigmatism. Note the "figure-8" pattern is symetrical around the centre. This is not keratoconus.
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Jagrut joined Roses in 2009 and became a shareholding partner in 2012. A passion for myopia management Jagrut is known for orthokeratology and keratoconus but also enjoys general optometry.
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Jacky started as a locum for Roses and has recently become a share holding partner in the business. With a solid background in all things optometry she has a particular interest in dry eye treatment but has a wide variety of skills in general optometry
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Jason joined us fresh from Auckland University in 2022. What Jason won't tell you is that he was the top optometry student of his cohort – quite an achievement. He is already excelling in keratoconus care and providing excellent care to his general patients.
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Another optometrist that joined our team straight from graduating. We share Ran with the hospital optometry team where she is expanding her knowledge regarding glaucoma. Ran is fluent in Mandarin which has helped us communicate effectively with our Mandarin-speaking clients.
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RGP Lens Insertion and Removal
Soft lens Insertion and Removal
Scleral Lens Insertion and Removal
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About the author
Powered by the New Zealand Eye Research Centre
Paul Rose who was the founder of Rose Optometry invented the Rose K lens for keratoconus. This website was developed for sufferers of keratoconus to learn about this condition. Most importantly we are here to help and we welcome enquiries no matter where you live in New Zealand or abroad. We are also here to support practitioners in learning to fit this condition.
Understanding Keratoconus
Keratoconus is an eye condition affecting the cornea, leading to an irregular shape and distorted vision. It often develops in teenage years but can start earlier or later.
The condition causes the cornea to thin and take on a cone shape over time. While typically painless, advanced stages may cause irritation. Severity varies, with some needing only glasses, others special lenses, and a few requiring surgery.
Keratoconus is considered genetic, often affecting multiple family members. Prevalence in NZ is around 1 in 175, with 60% being male. Maori and Pacific Island communities may experience higher rates.
Allergies, eczema, and asthma are common in those with keratoconus. Eye rubbing, especially from ocular allergies, should be avoided, as it can worsen the condition. Medications can help manage itching.
FAQ’s
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We are happy to answer any questions you may have. Feedback regarding this website is appreciated.
In general, spectacles do not provide the best level of vision compared to specialised contact lenses as they do not completely neutralise the corneal distortion. However, in early keratoconus spectacles may be a reasonable option. In more more advanced keratoconus spectacles may be recommended as a backup to contact lenses. If you have keratoconus, your optometrist can test you eyes for glasses and show you the level of vision they will provide.
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Contact lenses are generally considered to be the main-stay of keratoconus management. The main types are soft and RGP (rigid gas permeable) lenses. There are many variations of both soft and RGP lenses, some more suitable for early keratoconus and others for advanced keratoconus.
Due to the complicated nature of the keratoconic eye, it pays to check your optometrist is experienced in fitting contact lenses for keratoconus.
The initial fitting and follow-up process usually takes a number of visits.
New Zealand residents with keratoconus may be eligible for a Ministry of Health (MOH) subsidy towards the fitting and supply of contact lenses. Although the subsidy generally doesn't cover all the associated costs, it will significantly bring down the cost to the patient. The subsidy is managed between the optometrist and the MOH, so effectively the optometrist can make the application on behalf of the patient.
Aside from keratoconus, there are several other eye conditions that may be eligible for contact lens subsidy from the MOH. Generally these are conditions where fitting with contact lenses are the only viable option for the patient. Your optometrist can tell you whether you are eligible.
Generally a new patient will have a general eye examination before the fitting process commences. This is important to establish a number of things, including general health and medications (particularly how they relate to the eyes and/or contact lens wear). Also is helps establish the severity of the keratoconus and whether any other eye conditions are also present. Should the patient suffer from ocular allergy (hayfever in the eyes) this should be treated before contact lens wear is started. Your optometrist can prescribe the appropriate medication for this.
The general examination is usually followed by corneal topography to establish the exact shape of the cornea and severity of the keratoconus.
Should contact lenses be considered to be the best option a fitting appointment is made. Lenses are fitted to the eye and assessed with a microscope and to determine the correct shape. Many parameters have to be considered and this process is more technically demanding (and often time consuming) compared to fitting contact lenses for non-keratoconic eyes.
Once all the parameters (measurements) of the initial lenses has been calculated the lenses will be ordered from the laboratory. Most (but not all) contact lenses for keratoconus will be custom-made for the individual.
On receiving the lenses, the optometrist will check the initial fit and vision and have a contact lens assistant teach the process of insertion and removal to the patient.
After a period of adapting to the lenses (often about 2-3 weeks), the fit and vision with the lenses is evaluated and alterations made if required.
Regular followup examinations are required on an ongoing basis as the keratoconus often progresses. These reviews will usually take place about every 6 months.
Soft contact lenses are sometimes a viable option especially for mild keratoconus. As the cornea is irregular (misshapen) in patients with keratoconus soft lenses do not usually provide vision as clear or as stable as with RGP lenses (see below). Many patients with keratoconus will not be suitable for soft lenses as they may not provide adequate vision. Soft lenses come in many different designs and materials and may be disposable or custom made. The major advantage of soft lenses is that they are (generally) easier to fit and patients usually adapt to them quickly.
RGP are the mainstay of keratoconus management. As the lenses are rigid they don't conform to the irregular keratoconic cornea, thereby creating an regular front surface for the light entering the eye. This provides (in most cases) a far superior level of vision when compared to soft lenses.
RGP lenses are available in different designs and can vary greatly in size. The decision of what design, size and shape to use is dependant on the degree and type of keratoconus (and whether the patient has had surgery). RGP lenses require a greater level of skill and experience to fit (especially for keratoconus), so it is important your optometrist has expertise in RGP lens fitting.
Although keratoconus patients enjoy the excellent vision provided by RGP lenses, they do take longer for the eye to adapt to wearing them. It is normal to be very aware of the lenses for the first few weeks and it may take several months to be completely adapted to them.
These are a type of RGP lens designed to fit out onto the sclera (the white of the eye). The diameter of these ranges from about 13 to 16mm. The large diameter of these designs usually provide good comfort and stability as the lens tucks under the eyelids and lens movement is slight. Typically these lenses are reserved for more advanced forms of keratoconus as oxygen and tear exchange is reduced compared to standard (corneal) RGP lenses for keratoconus, and this requires careful monitoring. Worldwide clinical trials of the RoseK2XL semi-scleral design were completed in late 2010 with excellent results. The RK2XL was released commerically in 2013.
Combining soft and RGP lenses (know as "piggy-backing") is increasingly used in the management of keratoconus. It is used for 2 main reasons. The first is to improve tolerance (and speed up adaptation) to RGP lenses. In cases where despite the RGP lenses fitting correctly, the patient may still not gain sufficient tolerance to wear the lenses for the required length of time during the day. Refitting with a soft disposable lens underneath usually gives significant improvement in tolerance in these cases. This may be a temporary or permanent solution. The use of piggybacks also can be useful for those working in dusty environments. It is important to ensure that the system provides adequate oxygen to the eye, this is usually achieved by manufacturing both lenses in materials highly permeable to oxygen (so the eye can "breathe").
A hybrid lens is one that contains a hard centre with soft "skirt". The idea is to provide the benefits of both RGP and soft lenses. The parameters and materials available are somewhat limited - and the cost very high - meaning this type of lens has not gained widespread use in New Zealand.
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Keratoplasty
Also known as "corneal grafting" this procedure involves replacing your own irregular cornea with a donor cornea. There are several variations, most commonly penetrating keratoplasty (PK) and deep lamellar keratoplasty (DLK).
PK involves removing a full-thickness "button" of cornea about 8mm in diameter. The donor cornea is then sewn into place.
With DLK, the thin back layer of the cornea (called the endothelium) is left in place (so the incision does not quite go through all the layers) and the donor cornea is sewn into place on top of this.
As the donor cornea in foreign to the body, it is possible that the eye may try to reject the donor cornea. While this can usually be managed with medications (typically corticosteriod eye drops), is is probably the most significant reason for graft to "fail".
As DLK leaves the original endothelium intact, there is significantly less chance of rejection when compared to PK. However the visual outcomes (clarity) of PK tend to be better. Generally, which method of keratoplasty is performed is a decision made in conjunction with the ophthalmologist (eye surgeon).
One main reason for considering keratoplasty includes failure to able to maintain a lens on the eye. This is normally due to the keratoconus being so advanced that physically keeping a lens on the eye becomes impossible or risks damage to the eye. The other common reason for surgery is due to corneal scar tissue caused by the keratoconus reducing the vision significantly. Essentially, the cornea "stretchs" and develops scar tissue over the apex (peak) of the cornea. This creates a clouding of vision that contact lenses may not be able to correct effectively.
Keratoplasty is generally considered to be a last resort of patients with keratoconus. It is (almost) certain the a patient will still require either spectacles or contact lenses to correct the vision following keratoplasty.
CCL is a recently developed procedure designed to halt the progression of keratoconus. This is achieved by increasing the rigidity (stiffness) of the cornea preventing it from continuing to distort. The procedure itself (developed in Dresden, Germany), involves removing the thin surface layers of the cornea (epithelium), saturating the cornea with riboflavin (vitamin B2) dye, then treating the area with UV light. The UV reacts with the riboflavin to increase the bonding between the collagen fibres that make up the cornea. The effect is a greatly increased rigidity and resistance to progression of the keratoconus. It does not cure the keratoconus but prevents it getting worse. Collagen cross linking is an exciting procedure that should reduce the numbers of patients requiring keratoplasty (corneal grafting).
CCL must be performed before the keratoconus gets too advanced, therefore it is recommended all keratoconic patients with children have them tested for keratoconus (with corneal topography) from the age of 8. This will ensure that if keratoconus develops it is diagnosed early.
These are small semi-circular plastic rings that are implanted into the cornea. The idea is to "stretch" the central cornea, causing it to flatten and reduce the visual distortion. The results tend to be variable and although they may improve the vision to some degree in mild cases, they do not usually eliminate the the need for contact lenses. They are seldom of benefit in more advanced cases of keratoconus. However, they are able to be removed should the need arise.
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