Gas permeable contact lenses are a type of lens made from long-lasting plastic. These lenses take oxygen into the cornea and are also referred to as oxygen permeable lenses or rigid gas permeable (RGP) lenses, Before RGP lenses were introduced, contact lenses would be made from polymethyl methacrylate (PMMA). PMMA were hard contact lenses which are no longer in use.
Despite being excellent at providing vision, PMMA wouldn’t allow oxygen through. The cornea requires a constant source of oxygen for its health. Nevertheless, PMMA had the advantage of being made from excellent shatter-resistant material in response to glass. Gas permeable contact lenses carry the benefit of floating on a layer of tears and occupying approximately three-quarters of the area of the cornea.
They are Unique
Rigid gas permeable contact lenses are unique due to:
- The use of silicone - The advantage of silicone is that it allows oxygen in. The oxygen has direct access to the cornea. The current types of rigid gas permeable contact lenses enable the transmission of more oxygen into the cornea as opposed to some soft contact lenses.
- The size - The property of allowing in oxygen enables the creation of larger contact lenses compared to the previous smaller PMMA hard contact lenses. The oxygen factor also allows the closer fitting of the gas permeable contact lenses to the eye’s surface. Thus, gas permeable contact lenses offer more comfort and can easily be handled by the wearers. Besides, these lenses are safe to use in activities such as sports because they fit better on the eye.
RGP contact lenses carry several benefits which include:
- Deposits - They have lesser deposits than in soft contact lenses.
- Cost - They are less expensive since they have a longer life span.
- Hygiene - RGP lenses are easier to handle since they clean and quickly disinfect.
- Better vision - RGP contact lenses do not alter their shape when a wearer blinks. This is because they are made from a sturdy plastic material.
- Custom made - The eye care professional measures the cornea curvature and prescribes the most suitable lenses for each. This makes RGP lenses comfortable to wear.
- Durability - RGP contact lenses enjoy a longer lifespan than soft contact lenses. It is possible for RGP lenses to break, for example, when stepped on. Unlike soft lenses, they cannot be torn easily. The material used to make RGP contact lenses does not have water in it as contained in soft contact lenses. Unless a wearer’s prescription has changed, RGP lenses can last many years.
Indications and Selection Criteria
The following conditions may be ideal for RGP lenses:
- People with keratoconus - Keratoconus is a corneal dystrophy that leads to the thinning of the cornea. Consequently, the cornea forms a bulge or shape of a cone leading to extreme distortion in vision. Soft contact lenses do not provide vision in keratoconus patients. This is because they lack the smoothness and rigidity on the surface to correct an imperfect vision.
- Refractive surgery patients - Sometimes the prognosis from a refractive surgery may not look good. The patient can use custom-made gas permeable contact lenses to enhance vision. As in keratoconus, soft contact lenses cannot address this need.
- Ortho-K - People who want sharp vision without laser surgery can opt for Ortho-K. These RGP lenses have been specially created for wear at night while sleeping. The purpose is to reshape the cornea for clear vision in the morning upon waking up.
- Astigmatism - Astigmatism is a refractive error due to an irregularly-shaped cornea. Individuals with astigmatism see blurry or distorted images as the eye fails to focus equally on the retina. Such people may have also tried soft contact lenses with unsatisfactory results.
- Presbyopia - Presbyopia is a refractive error where the lens starts losing its focusing ability due to age leading to loss of near vision. Such individuals start experiencing some difficulty seeing objects like text on the phone. Presbyopia is often treated using bifocal, trifocal or progressive lenses. Gas permeable contact lenses can be fitted with numerous bifocal and trifocal designs.
- In the beginning, wearing contact lenses may feel uncomfortable. In contrast, individuals find soft contact lenses easier to handle due to their instant comfort. It takes a bit of time for the wearer to adjust to rigid gas permeable contact lenses.
- Gas permeable contact lenses need to be worn regularly. This is because prolonged periods away from them will require further readjusting.
- RGP lenses can easily get dislodged from the eye because of their smaller sizes. The lenses get dislodged mainly when an individual is engaged in an activity like sports. The risk is that the lenses can fall and get damaged or lost.
- Individuals with RGP lenses often deal with debris and dust. These elements easily find their way in because the lenses shift when the wearer blinks. The result is discomfort and a possible scratch on the cornea.
- RGP lenses need constant care to function properly. The care includes solutions, representing further expenses.