November 06, 2007
Correcting Astigmatism with Contact Lenses
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!
Posted by Vision at 04:04 PM | Comments (0)
June 24, 2006
Understanding Eye Care
Routine eye exams are important even for people who are not experiencing eye trouble. These are in-depth procedures that are usually performed by either an Ophthalmologist or Optometrist. How often a person needs an eye exam depends on a number of factors including age, overall health and whether or not eye disorders run in the family.
Children with no eye trouble need only have their eyes checked during routine visits to their pediatrician. This evaluation is commonly referred as a vision screening and should take place at a minimum, every 2 years. A vision screening is not as comprehensive as an eye exam, but it is invaluable in detecting early signs of eye/vision trouble.
For adults without eye trouble, eyes should be examined one time between the ages of 20-29, two times during the next 10 years, 2-4 times during the next 10 years and after age 65, eyes should be examined once every 1-2 years. People wearing corrective lenses should have their eyes examined yearly. Those with eye disorders should work out an examination schedule with their eye doctors.
What to expect from an eye exam
Using a light source, an external examination ensures the eyes 'look' right. You'll follow the doctor's pen (or other object) with your eyes to ensure the eye muscles function properly. When you read the illuminated chart with letters that get smaller the further down you go, your doctor is checking your visual acuity. If you need corrective lenses, you'll get a refractive assessment, a test that determines how light wave bend. The results of these tests help the doctor determine your prescription. He may put a Phoroptor, a device that resembles a big black mask, over your eyes in order to fine-tune these measurements.
Your peripheral vision will be tested. A slit lamp exam uses a microscope that emits a sharp beam of light to evaluate the cornea, lens and iris. The back of the eye is also examined and finally your eyes will be tested for glaucoma.
Ophthalmologist vs. Optometrist
The responsibilities and skills of an Ophthalmologist and an Optometrist are usually different, yet most people mistakenly use these terms interchangeably. Both professions involve eye care however the primary difference between the two is the presence of a medical degree. It is this degree that designates an Ophthalmologist as a medical doctor who has been trained in all areas of eye care including the ability to diagnose and treat eye disorders and diseases.
Ophthalmologists are qualified to perform eye surgery and they also know how to take proper eye measurements so they can accurately prescribe corrective lenses. Their training helps them dispense advice for preventing blindness and also enables them to assist those who are blind. In addition to advanced educational training, Ophthalmologists must be trained in clinical and surgical settings.
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Optometrists routinely perform eye examinations. During such eye examinations, Optometrists will also determine the need for, fit and prescribe corrective eyewear and/or lenses. Optometrists can also screen patients for certain eye disorders.
Posted by Vision at 09:48 PM | Comments (0)
