Contact lenses sit right on the surface of the eye and work to alter the path that light takes as it passes through the eye and onto the retina. The correct contact lens prescription can enable patients with refractive eye errors such as myopia (nearsightedness) and hyperopia (far-sightedness) to see clearly. However, regular contact lenses are not suitable for all patients, particularly those with certain eye conditions. When you undergo a contact lens exam, your eye doctor will be able to tell you if standard contacts will work for you, or if you will need what is known as specialty contact lenses. Specialty contact lenses are designed specifically for patients in which conventional contact lenses are unsuitable.
There are a number of different types of patients who may be unsuitable for conventional contact,s as a result, may be eligible for specialty contact lenses. These include patients who:
have been diagnosed with dry eye syndrome
have corneal scarring
have been diagnosed with keratoconus, a condition characterized by the bulging of the cornea
suffer from strabismus, a condition where the patient has an eye that turns in or out relative to the other
have suffered an injury to the eye
suffer from a peripheral corneal thinning disorder
are intolerant to other types of lenses
If you fall into any of these categories, your eye doctor will speak to you about the types of specialty contact lens that may work for you.
There are various different types of specialty contact lenses available, which is right for you will depend on your individual requirements. Your eye doctor will advise you which will be best for you. However, two types are more common than others. These are rigid gas permeable lenses (RGP lenses) and scleral lenses.
The name of this type of lenses gives two clues as to its defining features. Firstly, these lenses are more rigid than other types of contact lenses. This enables them to hold their structure more effectively, making them ideal to combat issues caused by abnormally-shaped corneas. This includes conditions such as mild keratoconus and astigmatism. However, they shouldn’t be confused with the older style hard lenses, which are virtually obsolete.
Secondly, the lenses are gas permeable. This means that they are made from a special material that allows oxygen to pass through them and reach the surface of the eye. This counteracts dryness and enables your eyes to ‘breathe’ better, making them better for patients who experience dry eye syndrome.
Other benefits of rigid gas permeable contact lenses include:
Sharper vision. Their rigidity and ability to hold their shape on the surface of the eyes mean that RGP lenses provide a clearer and sharper vision than soft lenses.
Greater stability. Their rigidity also gives them greater stability on the surface of the eye, meaning you are less likely to need to correct them during the day.
Slows myopia. Some research has found that the use of RGP lenses can actually slow the progression of myopia in children. This is known as orthokeratology and involves wearing lenses overnight that reshape the eye while they are sleeping, which also retain their shape during the day.
Long-lasting. Since they are rigid, RGP lenses are easier to keep clean and don’t need to be regularly replaced. In fact, with proper care, a single set of RGP lenses could last an entire year.
Scleral contact lenses are another very popular type of specialty lens. They're also a type of rigid, gas permeable contact lenses being made from exactly the same material. However, what makes them different is that they are available in various sizes, all of which are significantly larger than standard contact lenses and conventional RGP lenses. In fact, scleral lenses are anywhere from 14mm to 20mm in diameter, while conventional contact lenses are normally only 8-10mm in diameter. Scleral lenses are also designed to vault over the entire corneal surface and rest on the white part of the eye, called the sclera, leaving a clear space between the front of the eye and the back of the lens.
Scleral contact lenses make it possible for a number of patients who would otherwise not be able to wear contact lenses take advantage of this solution. This includes people who have damage to the front surface of the cornea, those who have significant corneal abnormalities, and those who experience chronic dry eyes. Their larger size also helps to give them greater stability on the surface of the eye, enhancing the clarity of the patient’s vision, and ensuring that they are easy to handle and comfortable to wear.
There are three different types of scleral lenses. Your eye doctor will be able to advise which will best meet your needs. These are:
Full scleral lenses. The largest type, these have the greatest amount of space between the surface of the eye and the back of the lens.
Mini scleral lenses. The mid-sized type, these make contact with the anterior part of the sclera.
Semi-scleral lenses. The smallest type, although still larger than standard RGP or conventional contacts, makes contact with the surface of the eye at the junction between the cornea and sclera.
For more information about specialty contact lenses and how we assess who makes a good candidate for this type of solution, please contact our optometry office in Rancho Cucamonga, CA.