Tecnis® Intraocular Lens
By Jennifer Kimberley
Presbyopia is an age-related vision problem that comes to everybody in mid-life. Most people, especially if they have had 20/20 vision thus far, find it annoying. Close-up vision becomes more blurry over the years so reading glasses are necessary. If you have always been nearsighted and worn glasses for distance, now you will need bifocals to improve your near vision.
Early in the 21st century a new type of treatment was introduced for presbyopia – the Clear Lens Exchange (CLE), which is also used to treat cataracts. This relieves you of having to keep track of eyeglasses. The CLE procedure replaces your eyes’ natural lenses with artificial lenses called Intraocular Lenses.
Although the exact causes of presbyopia are not fully understood, replacement of the eye’s natural lens does produce clearer vision at all distances. There are presently four brands of IOLs to choose from: Crystalens®, ReZoom™, ReSTOR®, and Tecnis®.
Of those four, Tecnis is the most recent, having received FDA approval in 2005. It is a multifocal IOL, as opposed to an accommodative IOL like Crystalens.
A Wavefront Data Design
The Tecnis IOL design is based on data gathered from a representative sample of the general population. Many people’s corneas and lenses were scanned using Wavefront technology. This is the technology used for diagnosis in a Custom LASIK procedure, and it is far more precise and detailed than the diagnosis that was used for the early LASIK procedures.
The early procedures used the same diagnostic method that is still used for determining a glasses prescription. Thousands of people have the same prescription as you might have, but nobody on the planet will have the same Wavefront diagnosis.
Each eye is diagnosed separately. A floor-standing Wavefront system shines a light into your eye and records the way it returns to the system, reflected back from your eye. When it enters your eye it is traveling in a straight formation; but when it returns it has been changed by the microscopic contours of your eye. It now has a Wavefront pattern that expresses your individual eye’s shape.
Lower and Higher Order Aberrations
The Wavefront system expresses this pattern in a colored three-dimensional map for each eye. If you were having a LASIK surgery, your doctor would use these maps to guide the treatment laser. The Tecnis manufacturer, Advanced Medical Optics (AMO), used this type of data to design an IOL that would correct two types of refractive error:
- The three lower order aberrations of nearsightedness, farsightedness and astigmatism
- Many of the higher order aberrations such as halos, ghosting, starburst and coma
The higher order aberrations are microscopically tiny defects in the eye’s contours that have never been corrected until recently. LASIK surgeries done in the 1990s did not correct them, and they were viewed as side effects of LASIK, as they were more evident after the lower order aberrations had been corrected.
Improved Night Vision
Custom LASIK and the Tecnis IOL correct both lower and higher order aberrations, giving you clearer vision at all distances and in all lighting conditions. They give you both:
- A greater quantity of clear vision (more distances); and
- A better quality of vision (no night vision problems).
Night vision (called scotopic vision) is provided by one type of retinal cell called rods. They do not perceive color, but do pick up contrasts and contours in dim light. Our bright-light vision is provided by retinal cells called cones, which do perceive color and give us our sharpest vision of details.
There have been many studies done on the effects of blue light on vision, some of them concluding that blue light should be blocked to help prevent Age-Related Macular Degeneration. To that end, eyeglasses, sunglasses, and contact lenses are available that block blue light.
However, many other studies have suggested that blue light is essential for good scotopic vision. As we age, scotopic vision declines whether or not the eyes have any other problems such as cataracts or retinal disease. If blue light is blocked, it can decline even further and make night driving more dangerous.
The Tecnis IOL Design
The Tecnis IOL is made of an acrylic material that does not block blue light. For more information about blue light, please see Circadian Photoreception.
When your eye surgeon inserts a Tecnis IOL, it is folded. Once it is inside the capsular bag that previously held your natural lens, it unfolds and your eye doctor will make sure it is correctly positioned.
The Tecnis IOL has a one-piece design with a square edge, as opposed to a graded edge. This helps to prevent any eye tissue from migrating beneath the IOL and clouding your vision. The edge is also frosted to reduce the edge glare that occurs with some other IOLs.
To learn more about the different types of IOL, and which one would be best for you, the first step is to consult with a qualified ophthalmologist. To find one in your area, please contact us today.