Contact lenses are an excellent method of visual correction that gives the user independence from eyeglasses. Contact lenses can be broken down into six basic categories, each with its own distinct advantages:
1. Soft contact lenses
2. Rigid gas permeable lenses (RGPs)
3. Hybrid contact lenses
4. Bifocal contact lenses
5. Scleral contact lenses
6. Orthokeratology contact lenses
1. Soft Contact Lenses: As the name would suggest, soft contact lenses are contact lenses that are made out of a flexible material, in contrast to gas permeable rigid lenses (see below) which are made out of a rigid material. Soft contact lenses are the most comfortable of all contact lens types and they are available in disposable and non-disposable varieties. Disposable soft contact lenses come in daily, 2-week and 1-month varieties. Daily disposable contact lenses are the safest and healthiest of all soft lens modalities and are great for dry eyes and for those who suffer from allergies. Daily disposable contact lenses are also the most convenient as the user does not have to deal with contact lens solutions and cleaning and does not require any contact lens storage case. Patients often report that there is nothing better than having a fresh, clean pair of lenses on every day. Daily disposable contact lenses are also recommended for those who want to wear contact lenses occasionally for sports or only on the weekends. By not reusing lenses that build up with protein deposits, daily disposable contact lenses are the most comfortable. Without the need and cost of contact lens solutions, and with the huge manufacturer’s rebates that are frequently offered, annual supplies of daily disposable contact lenses can cost about the same as 2-week disposable lenses. 2-week and 1-month disposable contact lenses as well as non-disposable soft contact lenses, require contact lens solution, cleaning and a storage case. Non-disposable soft contact lenses are rarely prescribed these days. They may be prescribed for a patient who requires a custom fit when disposable soft contact lenses do not work.
Toric Soft Contact lenses: If you have astigmatism, an eye condition that causes blurred vision due either to the irregular shape of the cornea or the curvature of the lens inside the eye, toric soft contact lenses will correct your astigmatism as well and therefore give you clearer vision. Toric lenses cost a little more than standard soft contact lenses and there are available in both disposable and non-disposable soft contact lenses.
2. Rigid Gas Permeable Contact lenses(RGPs): Rigid gas permeable contact lenses are made out of rigid (not soft) materials that allow more oxygen to pass through the lens material and to the eye. Though not as widely used as soft contact lenses, RGP contact lenses offer a number of advantages over soft contact lenses. Due to increased oxygen transmission, RGPs allow the eyes to breathe better. This reduces the risk of eye problems due to reduced oxygen supply that may be caused by some soft contact lenses. RGP contact lenses are also smaller than soft contact lenses so they cover up less of the front surface of the eye and move more on the eye, leading to increased and healthier tear exchange under the contact lens and to the cornea (front of the eye). RGPs also provide sharper vision than soft contact lenses because they provide a more stable and accurate correction of astigmatism. RGPs are more durable than soft lenses and can last up to 2 years so they don’t need to be replaced as frequently as soft contact lenses, making them less costly than soft contact lenses in the long run. Research has also suggested that wearing gas permeable contact lenses may slow the progression of myopia (nearsightedness) in children and teens. RGPs are also easier to keep clean and maintain and do not damage as easily as soft contact lenses.
So with all the advantages, why doesn’t everyone wear RGP contact lenses? There is a need for adaptation. The user may need 1 to 2 weeks to get used to them as there is some “lens awareness” initially. If a new user can tough it out those first few days, he or she will be pleasantly surprised by how good they can be. RGPs should not be worn part-time because they need to be worn everyday in order to stay comfortable. If a user stops wearing the lenses for a few days, he or she will be more aware of them on his or her eyes and will have to re-adapt to them. For patients with significant astigmatism, RGPs and hybrid contact lenses are the best contact lens types. RGPs also work best for those that have specialized needs such as keratoconus, post-trauma, poor refractive surgery outcomes and in other cases where soft contact lenses cannot provide good vision.
3. Hybrid Contact lenses: Hybrid contact lenses offer the best of both soft and rigid contact lenses. They are for those that want the clear vision of RGPs but cannot adapt to their comfort. The center of the lenses are rigid and the outside of the lenses are soft. They give the crisp, stable and consistent vision of RGPs as well as the comfort of soft contact lenses. Having the RGP in the center provides the increased oxygen transmission that RGPs are known for, as well as the correction of astigmatism. Hybrid contact lenses are excellent for those that need both bifocal and astigmatism corrected in one lens. They also work very well for those who have experienced unstable or fluctuating vision with soft toric contact lenses. Hybrid contact lenses have allowed some patients the ability to remain in contact lenses when they were previously unsuccessful wearing other contact lens types.
4. Bifocal Contact lenses: When a person is in his or her 40s, he or she may need to hold reading material, such as a menu or newspaper further from his or her eyes in order to see it clearly. This condition is called presbyopia, and it gets worse as we get older. Bifocal contact lenses are designed to provide relatively good far and near vision when a person reaches his or her 40s, correcting presbyopia. These lenses are available in soft, hybrid, scleral and RGP varieties. They have both the distance and near prescription within the lens creating a balance between clear far and near vision and most patients adapt very well to them. The designs that are available today are much better than those that were available just 5 years ago. For patients struggling with poor near or computer vision while wearing non-bifocal contact lenses, bifocal contact lenses are a great option.
5. Scleral Contact Lenses: Scleral contact lenses are large diameter rigid gas permeable lenses. They are the new revolution in contact lens technology and are becoming more popular among practitioners fitting patients with various corneal diseases including keratoconus. Scleral contact lenses are excellent in providing relief for patients who have been uncomfortable with traditional RGP lenses, and they can often help post-pone or eliminate the need for corneal transplants. The larger diameter of scleral contact lenses are fitted so that they do not touch the cornea (front surface of the eye) as it rests on the white part of the eye, making them more comfortable than traditional RGPs. Scleral contact lenses are ideal for conditions such as keratoconus, corneas that have been traumatized due to injury, or patients that have had bad outcomes with corneal or Lasik surgery. They are also ideal for those who have severe dry eyes as they act as a moisture chamber preventing the evaporation of tears. Scleral contact lenses are costly in comparison to other contact lenses, but they are well worth the relief they can offer a patient in need. Here is a link to get more information about scleral contact lenses: http://www.allaboutvision.com/contacts/scleral-lenses.htm
6. Orthokeratology Contact Lenses: Ortho k as it is widely known are contact lenses that are worn to sleep to temporarily change the shape of the cornea to correct one’s vision. It has become very popular for those who want to stop their vision from worsening (myopia control) as well as for those who want to free themselves from glasses and contact lenses all day. It is a non-surgical less expensive alternative to lasik and is completely reversible – stop wearing the lenses and your eye and vision returns to its original shape and state.
A Note About Dry or Red and Burning Eyes:
Patients with dry eyes may have trouble wearing any type of contact lenses comfortably with the possible exception of scleral contact lenses. It is best to treat dry eyes prior to wearing contact lenses.
Patients who wear contact lenses and tend to get red or burning eyes at the end of the day, may be experiencing a common problem caused by contact lens solution. Simply changing the contact lens solution to a non-preserved type may solve the problem.
Meyer Izaac, O.D.