Intacs Corneal Inserts or Implants:
A Proven Treatment for Keratoconus
Intacs corneal inserts or implants are a minimally invasive surgical option used primarily for the treatment of keratoconus.
Originally FDA-approved in 1999 for the surgical treatment of mild myopia (-1.0 to -3.0 diopters), Intacs are two tiny, clear crescent-shaped pieces of a plastic polymer that are inserted into the cornea to reshape the front surface of the eye.
The FDA in July 2004 granted Intacs a Humanitarian Device Exemption for use in the treatment of keratoconus largely because of Intacs' safety record and because only a few treatment options, such as corneal transplants, were available for keratoconus.
Intacs for myopia or keratoconus work by flattening corneal curvature. (Image: Addition Technology)
The approval allows Intacs to be marketed for reduction or elimination of myopia and astigmatism in keratoconus patients where functional vision is no longer obtained with contact lenses or eyeglasses.
In early January 2006, the FDA formally acknowledged that Intacs implants are therapeutic devices that can be described in company literature as corneal implants, rather than prescription inserts.
The corneal implants are designed for long-term vision correction. If you are among the 4 percent of people who are not satisfied with results or you have troubling visual symptoms, you can ask a surgeon to remove the Intacs.
Intacs can be replaced with different-size implants or removed for good. You have the option of replacing them with new rings at a later date if your prescription changes with age.
If Intacs are removed, vision tends to return to the way it was before surgery within three months. Those receiving replacement Intacs have obtained good visual results as well, and no serious problems with repeating the procedure have been reported.
How Do Intacs Work?
For treating nearsightedness, Intacs correct vision by flattening the cornea to refocus light rays and improve vision. For keratoconus, Intacs work by flattening the steep part of the cornea or cone to reduce vision distortions.
In a very few cases, however, eye irritation, blepharitis or abnormal blood vessel growth in the cornea (neovascularization) may occur. Also, Intacs may produce no corrective effect in fewer than 5 percent of individuals with keratoconus.
The procedure takes about 15 minutes and is done on an outpatient basis, but you will need someone to drive you home after surgery. Before surgery, your doctor places anesthetizing drops in your eye and may give you a mild oral sedative.
During the procedure, your surgeon creates a tunnel between layers of the corneal stroma, outside of the central optical zone.
The surgeon then chooses the appropriate ring thickness. A thicker ring in Intacs means more flattening of the cornea, which increases the level of vision correction achieved. After one or two crescent-shaped Intacs are inserted into the tunnel, the procedure is over.
After Intacs Surgery
You'll probably rest for a while, then go home (have someone else drive you). Most people have sharper vision the first day after surgery, but you may need a couple of days of relaxation to promote healing. You won't feel the ring segments, because they are beneath the cornea's nerve endings. Other people can't see them unless they look very closely into your eyes.
The ring segments flatten your cornea similarly to the way you can flatten the top of a tent by pushing on the sides. (Image: Addition Technology)
Results of these implants will depend on the degree of keratoconus in each individual. People with milder cases of keratoconus may not need any lenses for additional vision correction. People with moderate keratoconus may require glasses or soft contact lenses for improved vision.
For more advanced cases, rigid gas permeable contact lenses may be needed to improve vision or to delay or prevent the need for a corneal transplant.
Intacs can be very effective at changing the cornea and flattening the cone caused by keratoconus. But if you have advanced keratoconus, Intacs cannot halt the progression caused by weakening of surface eye tissue (collagen) responsible for corneal strength.
Research is continuing into an investigational procedure called corneal collagen crosslinking (CXL), which fortifies eye tissue to keep it from degrading.
Results of Clinical Trials for Intacs for Keratoconus
In 58 keratoconus eyes implanted with Intacs, almost half (25) achieved 20/40 uncorrected vision or better in a study reported in the October 2005 issue of Archives of Ophthalmology. Studies also have shown that Intacs may be able to reduce vision distortions in people with keratoconus who also have developed irregular astigmatism associated with an uneven eye surface.
In another study, single-segment Intacs improved both uncorrected vision and lens corrected vision for LASIK eye surgery patients who developed keratoconus or progressive corneal thinning (ectasia) as a complication. Single-segment Intacs also were more effective than double-segment Intacs in the same study reported in the May 2006 issue of American Journal of Ophthalmology.
Among 28 people in the post-LASIK study, 37 eyes were treated with either single-segment or double-segment Intacs. Each group was matched for factors such as age. The single-segment group averaged about nine lines of uncorrected vision improvement on a standard eye chart, compared with 2.5 lines in the double-segment group.
Results of Clinical Trials for Intacs for Nearsightedness
A literature review of 452 patients who underwent Intacs corneal ring implantation for the correction of nearsightedness was published in the October 2001 issue of Ophthalmology. Twelve months after surgery, 97 percent of treated eyes had 20/40 vision or better, and 74 percent had 20/20 or better.
Just under 9 percent of patients requested to have their Intacs removed due to side effects such as glare, halos and night vision problems or because their vision was under- or over-corrected, and 3.8 percent required a secondary surgical procedure. There were no serious complications.
A study of the reversibility of Intacs for nearsightedness, published in the January 2001 issue of Journal of Refractive Surgery, found that 20 of the 21 eyes returned to within 1.0 diopter of their preoperative refraction, with stable vision three months after removal was performed safely and without complications.
Are You a Candidate for Intacs?
If you are considering Intacs surgery for keratoconus, your first step is to have a comprehensive eye exam by an ophthalmologist who specializes in the procedure. He or she will examine your eyes and perform a number of measurements to determine if the procedure is likely to improve your vision.
If you are interested in Intacs corneal ring implantation for the correction of nearsightedness, you must be at least 21 years of age and have a stable eyeglasses prescription with no more than -3.0 diopters (D) of myopia and no more than 1.0 D of astigmatism.
After examining your eyes, your eye doctor can tell you more about Intacs. The cost of the procedure varies from surgeon to surgeon, but generally Intacs cost slightly more than laser vision correction.
[Read the latest prices for LASIK and other procedures.]
Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia. American Journal of Ophthalmology. May 2006.
Intrastromal corneal ring segments for low myopia: a report by the American Academy of Ophthalmology. Ophthalmology. October 2001.
Intrastromal corneal ring segments: reversibility of refractive effect. Journal of Refractive Surgery. January 2001.
[Page updated May 2013]
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