Contact Lenses
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.
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.
Contact Lens Subsidy
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.
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.
The fitting and followup process
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.
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.
Types of Contact Lenses for Keratoconus
Soft Lenses
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.
Rigid Gas Permeable (RGP) Lenses
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.
Semi-scleral lenses
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.
Combination systems
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").
Hybrid lenses
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.
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.
Rigid Gas Permeable (RGP) Lenses
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.
Semi-scleral lenses
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.
Combination systems
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").
Hybrid lenses
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.
