Astigmatism is a specific type of refractive disorder. If you are either near- or far-sighted, that means that your eye either focuses light too far in front of or behind your retina. When you have astigmatism, it means that your eye has an irregular shape, and as such, focuses light to multiple points. It is possible to have astigmatism and myopia or hyperopia, resulting in a corrective lens with two differing powers in the lens. Astigmatism correction needs to be aligned at a certain angle, or "axis" to properly correct your vision. Standard contact lenses can move or rotate on your eye without changing your vision. Astigmatism lenses are specially weighted to ensure that they sit on your eye a certain way. Because of this, astigmatism-correcting, or "toric" contact lenses are generally more expensive than standard or "spherical" contact lens.
A bifocal lens corrects for "presbyopia", a condition in which the lens of the eye looses elasticity, making it harder to shift focus for clear near vision. There are many different types and designs of contact lenses and eyeglass lenses to correct this, but most have one segment of the lens to correct your distance vision, and another segment to correct your near vision, or reading.
Color Contact Lenses:
A color contact lens has pigment in the lens which will change the natural color of your eyes. There are two different types of color contact lenses: Opaque and Enhancer. Opaque lenses are darker and have more pigment in them. They are designed to dramatically change the color of your eyes, even if your natural eye color is very dark. Enhancer lenses are lighter and produce a more subtle change. Enhancer lenses are primarily designed for people with lighter colored eyes. Since enhancer lenses are lighter, they do not make a noticeable difference on darker colored eyes. Opaque lenses come in a wide variety of colors. Enhancer lenses traditionally come in blue, aqua and green.
Concentric Ring Bifocal Lens:
Most bifocal contact lenses are made in this style. As the name suggests, the prescription in the lens varies in rings around it. Many of these lenses are designed with the distance correction in the center of the lens, and the reading prescription on the outside of the lens. Some manufacturers offer these lenses in both varieties, i.e. one lens has distance in the center and reading on the outside, while the other lens has reading in the center and distance on the outside. By manufacturing these lenses in both designs, this allows your eye care practitioner to help customize your prescription based on your specific visual needs. Some contact lenses are made in this design and have only one distance prescription and one reading prescription in them. Others have one distance prescription, and several concentric rings of differing power for reading.
Some people have problems with protein deposits building up on their contact lenses. Depending on the chemical composition of your tears, you may or may not have this problem. Protein deposits can be seen as tiny white spots on your contact lenses that won't rub off with standard cleaning. Most patients today use a multi-purpose solution which rinses, disinfects, cleans and stores their lenses. An enzymatic cleaner gives an added boost to your cleaning regimen. Often, these cleaners with include tablets that must be dissolved in your contact lens case, a hydrogen peroxide cleaning solution, and a special contact lens case with a metal disc in it. Some manufacturers make enzymatic cleaners that you simply need to drop on your contact lens and rub off, continuing your standard cleaning with a multi-purpose solution afterwards.
This condition is also known as Hyperopia. This results in close items appearing to be blurry, or the lens “over-working” for near vision, while distant items are clearer. With Hyperopia, the eye is "too short" or the cornea is too flat, and the lens focuses light behind the retina. A hyperopic prescription will have a "+" power associated with it.
This is also referred to as a visibility tint. Many contact lenses have a very light blue tint to them. This is designed to help make the lens more visible, thus helping you to handle the lens. A contact lens without a handling or visibility tint is completely clear, and can be harder to find in the case, or if the lens is dropped. A handling tint will not change your eye color, and will not appear blue to people looking at your eyes. If you wish to change your eye color, you need to purchase enhancer or opaqu colored contact lenses.
High-Index lenses are eyeglass lenses that have a higher index of refraction than a standard lens, thus making them thinner than a standard lens. There are many different brands and types of high index. Most high-index lenses have a number value associated with them, such as 1.56, 1.60, 1.67, etc. The higher the index of refraction, the thinner the lens will be. Of the three indexes listed above, the 1.67 would be the thinnest, and the 1.56 would be the thickest.
Hybrid Multifocal Lens:
This is a bifocal lens that has a hard, gas-permeable center, and a soft lens exterior. These lenses are not commonly used, unless the patient has specific needs that prevent a standard contact lens from working properly. Keratoconus, a corneal disease, may sometimes require this type of lens.
This is a method of correcting Presbyopia without using a conventional bifocal lens. With Monovision, one eye is corrected for your distance prescription, and the other eye is corrected for your near, or reading prescription. In some cases with monovision, the patient will actually only wear one contact lens to correct either distance or reading, with the other eye remaining uncorrected. Monovision can be initially disorienting affecting depth perception and general vision. With most patients, after a few days, the brain learns to rely on one eye for distance and the other for reading. Some people find this preferable to bifocal lenses. Monovision is traditionally only done with contact lenses, but on special occasions, monovision glasses can be prescribed at the discretion of your eye doctor.
As the name suggests, a multifocal lens has multiple prescriptions or focal points in it. Bifocals, trifocals and progressive lenses are all multifocal lenses. These are prescribed to correct Presbyopia, providing clear vision for distance, intermediate and reading all in one lens.
The technical term for this condition is Myopia. This results in distant items appearing to be blurry, while closer items are clearer. With Myopia, the eye is "too long" or the cornea is too steep, resulting in light being focused too far in front of the retina. A myopic prescription will have a "-" power associated with it.
Presbyopia is a natural condition in which the lens of the eye loses elasticity, making it harder to shift focus from far away to up close. Most people refer to this condition as "needing bifocals." As you age, this condition generally gets worse, requiring more magnification for reading. Presbyopia most often begins in your early forties, even if you have never required glasses before.
Also known as "special effects" lenses, these are opaque contact lenses that have a picture or design on them. They are popular for Halloween as well as in movies or television shows. Perhaps the most commonly seen theatrical lenses are "Cat Eye", "White-Out." Many of these lenses are available in a limited prescription range. Most theatrical lenses are clear in the center, allowing the wearer to see out of the center. Some specialty lenses (used for movies or television) are completely opaque, preventing the wearer from seeing out of them at all.
This refers to how often contact lens wearers throw away their lenses and replace them with a new pair. Contact lens replacement frequency varies by brand and manufacturer. The most common type of lens is a two week disposables. These give the wearer approximately 14 days’ worth of wear, at which point they are thrown away and replaced. Many other types of lenses exist; however, such as daily, one week, monthly, two month, three month and six month. It is important to ask your eye care practitioner what the replacement schedule for your specific contact lenses is, as wearing a lens for longer than it was designed for can lead to many different problems and ocular health risks.
RGP (Rigid Gas Permeable):
RGP's are an older style of contact lens. They are often called "hard" contact lenses, although the term "hard contact lens" generally refers to older PMMA lenses. RGP's are made of a much thicker and harder polymer than a soft contact lens. They are called gas permeable because gasses, such as oxygen can pass through the lenses. Older style "hard" lenses did not allow for the transmission of oxygen, so RGP's were a great improvement when they first came out. The concept of these lenses is that they reshape the refracting surface of the lens, providing clearer vision. These lenses are still prescribed today for patients with higher astigmatism, patients who has been wearing RGP's for a long time, or patients with a condition called keratoconus. Since the material from which they are made is much thicker and more durable than a soft lens, an RGP lens can have a wearing life of years.
Most contact lenses prescribed and dispensed today are "soft" lenses. Like an RGP lens, they allow for the transmission of oxygen, but they are made of a much softer, thinner material than an RGP. Soft lenses also contain a certain percentage of water. There are various different materials and polymers that are used to manufacture soft lenses, creating a variety of different lens types to properly fit different eyes.
Contact lens solution is a sterile liquid used in the care of contact lenses. Many solutions today are multi-purpose solutions. This means that they are used to store, rinse, clean and disinfect contact lenses. There are also solutions made that do only some of the above listed functions. There are many different brands and manufacturers of solution, the two most commonly-known in the US are Opti-Free and Renu. Be sure to ask your eye care practitioner which solution is the best fit for your contact lenses, as well as for your eyes.
Spherical lenses have only one type of correction in them. They can correct myopia, hyperopia and presbyopia. These lenses do not contain astigmatism correction. They refer to the eye's spherical shape. An eye needing astigmatism correction will have an asymmetrical or irregular shape.
Toric is a term for a corrective lens required for astigmatism. A toric lens will have different powers at specified angles, or axis in the lens. When you have astigmatism, it means that your eye has an irregular shape, and as such, focuses light to multiple points. Toric contact lenses must be weighted so that when they are placed in the eye, they will rotate to sit at the proper angle to correct your vision.
A Trifocal is a multifocal lens designed to correct vision to allow clear sight at three focal lengths. These are distance, intermediate, and reading. Trifocal generally refers to an eyeglass lens. Patients often refer to progressive lenses, or "no-line bifocals" as trifocals. This is not technically correct, as a progressive lens actually has more than three prescriptive powers in the lens.
Wear schedule refers to the amount of time each day that a contact lens may be worn for. New contact lens wearers or patients who have not worn contacts recently are often given a special reduced wearing schedule to help their eyes get used to contact lenses. Be sure to discuss your wearing schedule with your eye care practitioner. Different brands and types of contact lenses are approved for different lengths of wear time, and depending on your individual needs, your doctor may wish to prescribe you with a specific brand002E