Rigid Gas Permeable (RGP) lenses are the most prescribed hard contact lenses worldwide. They are more comfortable and safer to wear than earlier hard lenses, such as conventional PMMA lenses. RGP lenses are made from a hard plastic material that typically includes silicone. This lightweight material allows oxygen to pass directly through the lens to reach the front section of the eye, known as the cornea.
The cornea is the transparent, outermost layer of your eye, which refracts light and serves as the eye's outer layer. The cornea contributes as much as two-thirds of the eye's total optical power. (approximately 43 diopters). Maintaining enough oxygen to the cornea is critical to preserve eye health and avoid blurred vision and other eye-related problems.
There are several reasons why an eye care professional may indicate an RGP lens, from health and vision to cost-related factors. However, hard RGP lenses require specialized equipment for fitting, additional care, and frequent visitations with an optometrist. Compliance with your healthcare practitioner's guidelines regarding RGP lens management is paramount when prescribed as the preferred treatment strategy.
Conditions where RGP lenses may be beneficial include:
Myopia is an eye condition where light focuses in front of your retina that makes you see blurry when you look at distant objects
Hyperopia is an eye condition where light focus behind the retina, which makes you see blurry or experience eyestrain when you look at near objects
Astigmatism is caused by an irregular cornea and will cause distortion when looking at objects at a distance and near
Presbyopia is the gradual loss of your eye's ability to focus on nearby objects due to the crystalline lens inside your eye that loses the ability to change shape as you get older
Keratoconus is an eye disease where the cornea thins out and develops a cone-like shape. As a result of this corneal distortion, RGP lenses provide better vision compared to spectacles and soft contact lenses
- Corneal ectasia:
Corneal ectasia is a rare complication of laser eye surgery where your cornea is too thin. However, this often leads to irregular astigmatism, and RGP lenses can improve the quality of vision significantly
- Myopia progression:
Myopia progression occurs when near-sighted correction increases steadily throughout childhood. You can slow down myopia progression with a type of RGP lens called orthokeratology (ortho-K) lens
Most of the world currently wears disposable soft daily contact lenses; however, there are benefits to both soft and hard contact lenses. A vision specialist, also known as an Optometrist, can decide which contact lens and contact lens design is best suited for your visual needs, eye health and lifestyle.
Benefits of RGP lenses:
- Sharper vision
The lens is rigid, which provides a consistent, smooth surface, leading to crisper and clearer vision compared to specs and/or soft contact lenses. Soft contact lenses may change shape throughout the day as you blink and as they dry out. This may cause blurry and fluctuating vision.
- High prescriptions
Some patients may prefer RGP's because they were not satisfied with their vision in other vision correction designs. Often with very high prescriptions, particularly high astigmatism, the prescription may fall outside the range of soft contact lenses. Traditional soft contact lenses were limited in the power range they could correct; however, modern technology can better cater for most astigmatic lens corrections in soft contact lens designs. There are cases where an RGP lens is still indicated as it is custom-made to meet the exact specifications required.
- Highly customizable
Depending on your eye shape and prescriptions, your Optometrist specifies the power, diameter, curvature, tint, and other features of the RGP that are then ordered accordingly. Once the custom-made lens is fitted onto the eye, the Optometrist assesses if further adjustments to the RGP are required.
RGPs typically last a year or more with proper care as they are made of durable, rigid materials. They do not tear like soft contact lenses, although they can scratch, chip or crack if not handled properly.
Because RGPs generally last longer than soft contact lenses, the cost of wearing hard lenses reduces over time. However, if the lenses are not well cared for or the lens prescription and design need to be changed, the costs increase significantly. Due to the higher initial cost of purchasing RGPs, and re-makes due to breakage or change in prescription, RGPs are most commonly prescribed as a necessity when other lens treatment options are no longer suitable.
- Avoids dehydration
As RGPs are made from a hard water-insoluble material, the lenses can not dehydrate, which, unlike traditional soft contact lenses, often results in blurred vision due to dehydration. Modern soft contact lens materials resist dehydration with moisture lock technology, improving end-of-day comfort and maintaining clarity throughout the day.
Despite the pros and cons associated with contact lenses, it is important to understand which visual corrective treatment options best suit your eyes. Your visual requirements, lifestyle or other factors which may be important should be considered before deciding on the best treatment option. An optometrist is an eye care professional specialising in vision correction and will always have a specific reason why they would prescribe a soft vs a hard RGP lens. It is advisable always to be part of these discussions and follow the guideline from a qualified eye care professional.
Disadvantages of RGP contact lenses:
- Initial discomfort
As RGPs are made from a rigid material and thicker than soft contact lenses, initially, patients report tearing, blurred vision and discomfort. Soft contact lenses are thinner and more comfortable for new contact lens wearers, hence why so many patients prefer soft contact lenses, among other reasons. Despite the initial discomfort, an optometrist will better understand the lens type best suited to a patient's visual needs.
- Longer adaptation
Due to the steep adaptation phase commonly associated with RGP lens wear, soft disposable or daily contact lenses are usually prescribed as the more convenient and easier vision care option, for both patient and practitioner.
- Highly customizable
Depending on your eye shape and prescriptions, your Optometrist specifies the power, diameter, curvature, tint, and other features of the RGP lens to be ordered. The lens is custom-made, and once fitted onto the cornea, the Optometrist will assess if any adjustments need to be made.
- Smaller size
RGPs are smaller than soft contact lenses, have a higher risk of falling out of your eye, and are more difficult to handle initially. Over time, the handling of contact lenses improves, and the lens size should no longer be an issue.
As RGPs are smaller and rigid, they do not conform to the shape of your eye like soft contact lenses. As a result, foreign objects are more likely to get trapped underneath the lens, and it is important to exercise caution when you are exposed to dust, sand, and other irritants.
Compared to daily disposable soft contact lenses, RGPs require cleaning, maintenance and greater care to avoid vision and potential eye health problems. Poor RGP lens hygiene and care also result in significantly higher financial costs associated with lens replacement.
Tips for RGP wearers
Follow the guidelines from your eye care professional regarding the wearing and the aftercare schedule regarding the use of RGPs as part of your vision care plan. Seven tips for safe RGP usage:
- Ensure you have a full eye examination with your Optometrist at least once a year
- Avoid tap water or saliva to rinse your lenses
- Only use appropriate cleaning, storing, and disinfecting solutions
- Replace your contact lens case regularly
- Do not sleep, swim, or shower with RGP lenses
- Check for cracks and chips before inserting
- If you get dust or other debris in your eye, remove the RGP lens immediately and rinse your eye with sterile saline