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Other Procedures
Keratoconus
The cornea is the clear front part of the eye, and functions much like
a window that you look through, except that it is a living structure. It is composed
of many thin stacked layers of protein (collagen) and supporting cells (keratocytes)
that keep the protein fibers strong.
In the condition known as 'keratoconus', the cornea becomes gradually
thinner in its center. Then, the normal fluid pressure in the eye causes this
area to bulge forward (like a thin area on tire).
On the outside of the eye, this bulging causes the cornea's normal round curvature
to become more irregular. Patients with keratoconus gradually develop distorted
vision. Because the cornea's bulging has an irregular shape, glasses and conventional
contact lenses cannot provide clear vision.
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Rigid gas permeable contact lenses are one option for keratoconus. As the name
implies, these lenses have a rigid shape, allowing them to create a new, smooth
front surface for the eye. They can provide acceptable vision, but for some
people the contacts can become very uncomfortable and can easily fall out.
This type of lens is also considerably more costly than soft contact lenses.
In the past, when rigid contact lenses failed, the only other option for treating keratoconus was corneal transplantation. This procedure requires a recovery period of six to 18 months before stable vision can be achieved. After recovery, many patients still require rigid contact lenses to see well.
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Intacs is the newest treatment for keratoconus among patients who can not tolerate contact lenses. Intacs are tiny (0.25 mm thickness) acrylic rings that are placed between the layers of the cornea. These rings were first designed to treat nearsightedness, and they are currently FDA approved only for this use.
However, they have been the subject of considerable research in keratoconus, and several studies have shown they can help provide a more normal shape to a patient whose cornea is weakened by keratoconus. The FDA is currently reviewing the approval of Intacs for keratoconus, and approval is expected by the end of 2004.
Like a corneal transplant, Intacs rings actually add structural integrity to the cornea, which is lacking in keratoconus. This treatment can be performed as an outpatient and allows a much quicker recovery than corneal transplantation.
The Intacs Procedure
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Step One:
An incision is made to a depth of 80% of the corneal thickness using a precisely calibrated instrument with a blade made of diamond.
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Step Two:
Through this incision, the surgeon creates channels (tunnels) through the corneal tissue for the rings to be placed.
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Step Three:
The acrylic rings are introduced into the channels. When in place, these rings alter the cornea's shape, creating a more normal surface contour.
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Results
Both in the U.S. and abroad, studies on the effects of Intacs on keratoconus have shown that the cornea may take on a more regular, round shape after the rings are implanted. Results depend on the individual patient's corneal shape, but roughly half of patients who have the rings placed have an increase in uncorrected vision of about five lines on a standard Snellen eye chart. This is the equivalent of vision improving from 20/200 (legal blindness) to 20/50 (acceptable for driving in most states). Corrected vision increased by about three eye chart lines in most patients.
A thorough eye exam by a corneal specialist is necessary to determine if an individual is a candidate for Intacs for keratoconus. For information on Intacs at Harvard Eye Associates, please contact us .
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