IntraCor – An Inside-the-Cornea Laser Treatment for Presbyopia
Many people over age 40 seek laser eye surgery to correct presbyopia, or the loss of the ability to see near objects clearly due to normal aging of the eye.
A new "inside-the-cornea" (intra-corneal) laser procedure called IntraCor may soon become a popular presbyopia correction surgery. Though the FDA has not yet approved IntraCor for use in the United States, the procedure has shown promising results in early studies conducted in Europe and South America.
The IntraCor procedure corrects vision by using a femtosecond laser (Technolas Perfect Vision, Munich, Germany) to alter the curvature of the cornea. The laser treatment takes place entirely within the cornea, without the need to create a corneal flap (as in LASIK) or remove the outer layer of the cornea (as in PRK or LASEK).
Because IntraCor is entirely intra-corneal, the new femtosecond laser procedure eliminates the risk of certain LASIK complications, such as partial flaps and other flap problems. It also essentially eliminates post-operative discomfort and reduces the risk of eye infections after surgery, since there is no open wound created on the eye.
And because the IntraCor femtosecond laser does not ablate (vaporize) significant amounts of corneal tissue like an excimer laser used LASIK and other laser vision correction procedures, corneal thickness remains essentially unchanged. Therefore, IntraCor is less likely to cause a weakening of the cornea, which in turn can lead to a rare but serious complication of LASIK called ectasia.
Currently, the IntraCor procedure is being investigated outside the United States, and only for the correction of presbyopia, with or without mild amounts of farsightedness. But researchers feel the procedure may some day be modified to correct nearsightedness as well. Corneal implants and inlays provide other types of treatments to the internal layers of the cornea for the correction of presbyopia without the need to eliminate significant amounts of corneal tissue.
How IntraCor Works
To correct presbyopia, the IntraCor femtosecond laser creates a series of concentric rings in the interior of the cornea. The outer layer of the cornea (called the epithelium) is left untouched.
These laser-produced internal rings steepen the curvature of a small central zone in the cornea, and this gives the eye added magnifying power required for reading and other near vision tasks.
Outside the central near zone, the cornea gradually changes shape to expand depth of focus for computer work and other tasks at arm's length. The cornea outside the largest ring produced by the laser maintains the proper shape for clear distance vision.
In many respects, IntraCor is similar to Presby-LASIK for the correction of presbyopia. But IntraCor has the added advantage of being less invasive, since the procedure takes place entirely inside the cornea and no corneal flap is needed.
The IntraCor Procedure
Like LASIK, the IntraCor procedure is performed on an outpatient basis and requires only local anesthesia (numbing eye drops). If you desire, your eye surgeon also can give you a mild oral sedative to relax you prior to surgery.
The procedure only takes only a few minutes, but you should plan to be at the surgery center for an hour or two.
Basically, the steps of the IntraCor procedure are:
- Measurements of your eye are entered into the laser's computer.
- Eye drops are applied to your eye to reduce the risk of discomfort.
- The center of your cornea is marked with a device to help center the laser.
- A sterile disposable contact lens is placed on your eye with a suction ring.
- The laser beam is directed through the contact lens in a concentric ring pattern. This step takes less than a minute.
- Immediately after the laser treatment, the suction ring and contact lens are removed.
IntraCor can be performed on both eyes or on just one eye, depending on your needs.
IntraCor Safety and Effectiveness
Colombian eye surgeon Luis Ruiz, MD, performed the first IntraCor procedure for the correction of presbyopia in October 2007.
Recently, Dr. Ruiz and colleagues conducted a study of 83 eyes of 45 presbyopic patients who underwent the IntraCor procedure at his practice in Bogota. Patients in the study ranged in age from 44 to 67 years, and the follow-up period after surgery was 6 to 12 months.
Six months after surgery, all 83 eyes had improved uncorrected near vision (UNVA), with little or no loss of uncorrected distance vision (UDVA). A total of 22 eyes were available for evaluation 12 months after surgery. Of these, 89 percent achieved 20/25 or better UNVA and UDVA.
All patients reported seeing halos after surgery, especially at night, but only a few patients reported difficulty driving at night because of halos. Complaints of halos diminished over time, and at one year after surgery few patients noticed them.
A second IntraCor study was conducted recently by German researchers at the University of Heidelberg.
In this study, 25 eyes of 25 presbyopic patients were evaluated. Patients in the study ranged in age from 47 to 67 years, and the follow-up period was three months. All patients received the IntraCor procedure on only their non-dominant eye.
The mean uncorrected near visual acuity in these eyes improved from 20/100 prior to surgery to better than 20/40 after the IntraCor procedure. Slightly more than 54 percent of the patients achieved at least 20/25 uncorrected distance vision and were able to read newspaper print without glasses.
In all cases, post-operative healing was uneventful and the cornea of the treated eye was clear within a few hours after surgery.
The Future of Refractive Surgery?
IntraCor shows promising early results for restoring near vision lost to presbyopia, and IntraCor may soon become a popular alternative to other surgical procedures that correct presbyopia.
Currently, IntraCor is not designed for the correction of myopia, which is the refractive error affecting most people who seek vision correction surgery. But that may change.
In a recent interview with Review of Ophthalmology, Dr. Ruiz says he feels refractive surgery will move toward IntraCor and other intra-corneal laser procedures in the future because of the noninvasive nature and safety advantages of these procedures.
SOURCES:
1. Intrastromal correction of presbyopia using a femtosecond laser system. Journal of Refractive Surgery. October 2009.
2. Early outcomes of INTRACOR femtosecond laser treatment for presbyopia. Journal of Refractive Surgery. October 2009.
3. Surgery goes from bladeless to woundless. Review of Ophthalmology. December 2009.
Note: This information is for general education purposes only. It is not to be used as a substitute for medical advice from your eye doctor or refractive surgeon.
