Correcting Astigmatism with Contact Lenses

May 15, 2008 by  
Filed under VISION

Astigmatism for a long time was an eye problem that could not be fully corrected with contact lenses. Mild astigmatism could be adequately improved with soft contact lenses, but there weren’t options for more severe cases. The eye problem itself results from a misshaped cornea – rather than being spherical like a ball, the cornea in people with astigmatism is oblong, shaped more like a football. Because of this shape, light rays can’t refract properly against the retina. Instead of focusing the rays on one spot, the odd shape causes light to refract in multiple locations on the retina, causing the blurred vision, regardless of distance, that is symptomatic of astigmatism.

Understanding toric contact lenses

The development of toric contact lenses opened up a whole new world of vision for people with astigmatism. Toric contact lenses don’t look any different than other soft or rigid gas permeable contact lenses, but in fact they are very different. The lenses consist of a number of different curvatures in various meridians or sections on the lens. Since astigmatism is a problem involving unbalanced meridian sections (due to the odd shape of the cornea) bringing the meridian sections back into balance is what helps produce clear vision.

Since the positioning of the various curvatures is key to improving vision, toric soft contact lenses cannot rotate – they must be held in a certain position in order to be effective. This is accomplished several ways. One way is to add weight to the bottom of the lens by building up or thickening that section. Another way is to make the top part of the lens lighter, by thinning this section.

Rigid gas permeable lenses are an option

Yet another way to correct astigmatism with contact lenses is to use rigid gas permeable lenses. These lenses are not as flimsy as soft lenses and that enables them to hold onto their shapes, even after blinking. Regular gas permeable lenses work effectively at correcting mild to moderate astigmatism, but in cases where the astigmatism is severe, it’s usually necessary to purchase gas permeable toric contact lenses. Toric lenses are custom shaped so that the inside of the lens more closely matches the shape of the astigmatism. Because of the customized fit, toric lenses remain in position and rotation isn’t an issue.

And because toric contact lenses involve customization, you’ll likely have to pay more for this type of contact lens. You might even find that your eye doctor charges more when fitting you for toric lenses because of the extra work involved in properly measuring each eye.

If you work with an eye doctor you trust, he or she will likely first try to prescribe regular contact lenses to treat your astigmatism. Again, mild and moderate astigmatism can usually be adequately corrected with standard lenses. Only when the astigmatism becomes severe is it necessary to resort to toric style contact lenses. When this happens, you’ll find that toric lenses are available as daily wear, extended wear, silicone hydrogel and disposable brands. They even come in an assortment of eye color options!

The Different Types of Contact Lenses

February 22, 2008 by  
Filed under VISION

The types of contact lenses available today are nearly as numerous as the corrective issues they’re designed to correct. But today’s contact lenses don’t even need to be corrective in nature. Many are purely aesthetic, enabling a wearer to change eye color from brown to violet, for example, or to change from the appearance of human eyes into eyes that resemble that of a cat or wolf or even an alien!

Contact lens prescriptions include information on proper fit, measuring such attributes as curvature and diameter. But the prescription also contains other pertinent information such as proper measurements for correcting vision as well as the brand of contact lens believed most suitable for the patient’s situation.

It’s not necessary to understand all the different makes and models of contact lenses. That’s more the responsibility of vision specialists since they’re the ones responsible for making the final determination based on their training, knowledge and past experience.

There are several ways to categorize contact lenses. One way is to categorize contacts by material type. Plastic is the material of choice when it comes to contact lenses. Its fluid nature enables a more comfortable fit and its availability makes contact lenses more affordable. Plastic lenses fall into 3 general categories including gas permeable, hard and soft.

Another way to categorize contact lenses is by their wear and replacement schedules. As for wear schedules there are daily wear and extended wear lenses. Daily wear lenses are designed to be inserted and removed every day whereas extended wear contact lenses can remain in place for one to several weeks before removing.

And based on replacement schedules, there are disposable contact lenses and non-disposable. Daily wear disposable are worn once and then throw right away, completely eliminating the need for cleaning. Regular disposable contacts are worn several weeks before being thrown away. Again, the goal with disposables is less maintenance which lowers the risks of infection and other eye problems. Non-disposables require careful and regular maintenance as they don’t get replaced until torn or until a patient’s prescription changes.

And finally there are some special kind contact lenses. Theatrical contact lenses started out being designed for and used by actors and other performers. Giving eyes the ability to change from normal-looking to horrific and demonic, theatrical lenses are gaining in popularity among everyday users. Used primarily as a way to change a person’s look, the lenses generally are not designed for corrective purposes, but they do require a prescription for proper fitting.

Besides theatrical lenses, there are contact lenses that offer protection against damaging ultraviolet light – lenses called varichrome that darken when exposed to bright sunlight making sunglasses an unnecessary accessory, and contact lenses designed to change the color of one’s eyes.

Then there are the specialized contact lenses such as toric lenses that correct more troublesome astigmatisms, bifocal contact lenses which help a person see both close up and far away, spherical or aspherical lenses, and monovision lenses in which one lens assists with close up vision and the other lens is dedicated to distance vision.

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NOTE: The contents in this blog are for informational purposes only, and should not be construed as medical advice, diagnosis, treatment or a substitute for professional care. Always seek the advice of your physician or other qualified health professional before making changes to any existing treatment or program. Some of the information presented in this blog may already be out of date.