Hard contact lenses
Hard contact lenses (also called RGPs) often provide clearer vision than soft lenses.
Hard contact lenses (also called Rigid Gas Permeable or RGP contact lenses) have declined in popularity in the past few decades due to the rise of soft disposable lenses that can be replaced as often as every day. But RGPs still have an important role to play, especially in fitting irregular corneas.
If you have keratoconus, or have had a corneal transplant, your cornea will not be a regular shape. As the cornea (the clear front surface of your eye) is the part used for focusing, this means your vision won’t be sharp, even with glasses. RGP / hard contact lenses are rigid, and provide a smooth and regular surface to your eye. Your tears fill in the gaps underneath the lenses and effectively your eye becomes a regular shape and clear vision is possible.
The RGP advantage
Not only is vision sharper with hard lenses, they are made from oxygen-permeable material, which usually means you can wear them all day every day. Your cornea is clear and has no blood vessels of its own. It gets its oxygen from the air via your tear film. When contact lenses are worn, less oxygen gets to the cornea. This is why you may be advised to only wear your contact lenses for a certain number of hours per day. RGP or hard lenses allow the cornea to breath and maintain good corneal health.
Why doesn’t everyone wear hard contact lenses? you may ask…
This type of contact lens requires expert fitting to achieve comfortable vision. They also require getting used to when you first get them. You may need to build up your wearing time by an extra hour per day until you are comfortably wearing them all day.If you can get a disposable lens that does the trick, why would you bother?
Uses of hard contact lenses
These lenses are most commonly used where the surface of the eye is irregular. This may be due to diseases such as keratoconus, or, procedures such as corneal transplant. You cannot achieve a clear focus with an irregular cornea, even with glasses. These contact lenses create a smooth surface and clear vision is restored.
Keratoconus and RGPs
One of the most common uses of RGP hard contact lenses is in the management of keratoconus. They are in fact the mainstay treatment for keratoconus. RGP lenses for keratoconus come in a range of designs:
These may be smaller or larger diameter, depending on the unique characteristics of your eye, but they only touch your cornea.
These are larger than corneal designs, and extend onto your sclera. This can greatly enhance comfort and provide better vision
These are the largest of all and only touch the white of your eye, completely vaulting the central (often very sensitive) surface of your eye. These used to be the lenses we turned to when all else had failed but they provide such clear, comfortable vision, they are often our lens of choice for a sensitive or very irregular eye.
Corneal Transplant and hard contact lenses
Sometimes, if the cornea has become scarred or can no longer provide clear vision, even with contact lenses, you may need a corneal transplant. Grafts are best avoided for as long as possible, but can be a sight-saving procedure when indicated. After a corneal graft, your eye will have an irregular surface and much clearer vision may be possible through the use of specialised RGP lenses.
Who fits hard/RGP contact lenses?
Specialised RGP lenses are fitted by an advanced contact lens practitioner who sees corneal disease patients regularly. At The Eye Practice, we see irregular corneas day in, day out.