Intacs® Intraocular Rings and Keratoconus

Intacs is a corneal prescription ring insert used for patients with low myopia and more recently, keratoconus.  Placement of Intacs prescription inserts is entirely reversible.  Thus, patients who elect to have Intacs placed in their eyes are not “locked in” to the procedure forever, as are patients who undergo certain other refractive procedures such as LASIK, where corneal tissue is actually removed by the excimer laser.

Vision correction with Intacs entails implanting the micro-thin intracorneal rings into the cornea by a trained eye surgeon. Intacs produce a reshaping of the curvature of the cornea, reliably reducing low degrees of myopia (nearsightedness). Intacs cannot be felt by the patient, require no maintenance, and are probably less visible than a contact lens to the naked eye. Intacs have been studied for about 15 years and are FDA approved. The primary drawback at the present time is two-fold: 1) Intacs are only available in the U.S. for low degrees of myopia (-1.00 to –3.00 diopters) and 2) this procedure has never gained widespread public acceptance, almost certainly because it has been greatly overshadowed by LASIK, thus making access difficult.  As such, few eye surgeons are implanting Intacs at this time.
 

Intacs are prescription inserts, which can be removed or replaced if one’s vision needs change or there is any dissatisfaction with the corneal ring inserts. In the U.S. clinical trials, all of the very few people who had Intacs removed could subsequently be corrected to 20/20 or better vision.

Indications for Intacs

Intacs inserts is intended for the reduction or elimination of mild myopia of –1.0 to –3.0 diopters in patients who meet the following additional criteria:

• 21 years of age or greater
• documented stability of refraction as demonstrated by a change of refraction less than or equal to 0.50 diopters for at least 12 months prior to the preoperative examination
• the astigmatic component of the refraction is +1.0 diopters or less

Visual Results

Amazingly, 53% of patients see 20/16 or better as a result of their primary procedure and 34% see 20/20 or better the day after the procedure! One month after surgery 79% of patients see 20/25 or better and by one year 87% of patients see 20/25 or better. Fully 97% of patients are 20/40 or better one year following surgery (20/40 is a "benchmark" of visual acuity as this level of vision allows unrestricted passage of a driver's license test in most states)[i].

Furthermore, placement of Intacs maintains the “normal” positive asphericity (shape) of the cornea whereas excimer laser procedures such as LASIK and PRK frequently produce oblate corneas. The latter condition may result in reduced contrast sensitivity. Visual correction with Intacs is also rapid and stable. Eighty percent of patients have 20/40 or better vision the day after surgery. A year after surgery, over 50% of patients see 20/16 or better as a result of their first procedure, i.e., without enhancements. 

The Procedure

Intacs corneal ring prescription inserts are placed within the substance of the cornea under topically applied (eye drop) anesthesia. No needles or injections are required. Some patients may experience mild and temporary discomfort during the procedure. The surgeon makes a tiny incision in the top of the cornea, creates a 180 degree tunnel in which to place the first prescription insert, and then places the Intacs ring in the corneal tunnel. A similar procedure is used to place the second Intacs ring.

Two Intacs inserts are placed in each eye, each of which approximates a near half-circle. The tiny incision through which the Intacs is placed is usually closed with a single stitch that can be removed within a few days or weeks. The entire procedure usually takes about 15 to 20 minutes per eye.

What to Expect After Surgery

The day of surgery, the operated eye may feel somewhat scratchy and vision may be blurred. Do not be alarmed. Any discomfort will usually be relieved by anti-inflammatory eye drop medications. You will be instructed to use both antibiotic and steroid eye drops, generally for about two weeks following surgery. On the first postoperative day, vision is usually good enough to drive a car, i.e., 20/40 or better, but may be reduced if the eye remains dry or an abrasion of the corneal surface has occurred. 

You will not be able to feel your Intacs inserts, however, you may feel the tiny incision and or stitch as the incision heals. This will usually resolve within a couple of days. If a suture was placed, your surgeon will probably remove it in about 2 to 4 weeks. With Intacs prescription inserts, you may expect your vision to recover very quickly and to continue to improve for up to 6 to 12 months.

Intacs® Prescription Inserts for Keratoconus

Defining Keratoconus

Keratoconus is a corneal degenerative disorder, in which the cornea becomes progressively thin and steep, resulting in irregular astigmatism. The front of the eye, therefore, is "bulging" and irregular in topography. The presenting complaint is poor vision and inability to correct vision well with glasses, and sometimes, contact lenses. Only about 10% of patients have a positive family history of keratoconus. However, 90% of cases are bilateral suggesting a possible genetic basis. The condition usually presents in the teenage years and has a variable progression.

Diagnosis of Keratoconus

Keratoconus may be difficult to diagnose in the early stages. One of the most reliable methods of detection, however, is corneal topography. This diagnostic procedure is routinely completed prior to refractive surgery. If the patient is found to have keratoconus, refractive surgery, such as LASIK, is generally contraindicated as the outcome of such surgery may be unpredictable. In the more advanced stages of keratoconus, the diagnosis may be made with a slit-lamp microscope by observing the grossly distorted and thinned cornea. 

Management of Keratoconus 

In the early stages of keratoconus, most patients achieve good vision with glasses. As the condition progresses, many patients require rigid gas permeable contacts for successful correction.  In advanced stages, the patient may develop the condition known as acute corneal hydrops, which represents sudden development of corneal edema (swelling) due to rupture of Descemet's membrane, a membrane near the posterior (deep side) of the cornea. The acute episode often resolves but results in corneal scarring and, perhaps, permanent visual reduction. At this stage, the patient will most likely be referred to a corneal specialist in consideration of corneal transplantation.

Intacs for Keratoconus

When patients fail to achieve adequate vision with glasses or contacts, then Intacs prescription inserts may be placed in an attempt to improve visual acuity and delay or prevent the need for corneal transplantation.  The U.S. FDA gave a “humanitarian device approval” for the insertion of Intacs for this purpose on July 26, 2004[ii]i].  The Intacs prescription insert has been shown to help flatten the bulging cornea in some patients with keratoconus, thereby improving visual acuity and postponing the need for corneal transplant.  The FDA states that Intacs inserts should not be used in keratoconus patients who:

• can achieve functional vision on a daily basis using eyewear
• are younger than 21 years of age
• do not have clear central corneas
• have a corneal thickness less than 450 microns at the proposed incision site

In what is probably the largest study published on the use of Intacs prescription inserts for the treatment of keratoconus, seventy-four eyes of 50 subjects were evaluated following placement of Intacs[iiiii].  Patient ages ranged from 20 to 73 years.  In most cases, a thicker Intacs ring segment was placed inferiorly (lower) in the cornea along with a thinner Intacs segment superiorly (higher).  This is because, in most cases, the “cone”, or the bulging aspect of the cornea, is located inferiorly. 

The mean (average) preoperative uncorrected visual acuity was about 20/250, which improved to a postoperative mean of about 20/80.  That is, on average, patients gained about four lines of uncorrected vision on the standard Snellen eye chart that is used in most doctors’ offices.   In patients with keratoconus and corneal scarring, the mean pre-operative best-corrected visual acuity was about 20/150, which improved to about 20/65 postoperatively.   This indicates that this group improved about five lines on the eye chart.  The study group concluded that, “Intacs implantation can improve both uncorrected and best spectacle-corrected visual acuity and can reduce irregular astigmatism in corneas with and without corneal scarring.” 

Conclusion

Intacs prescription inserts have shown excellent results in the treatment of low degrees of myopia.  However, I believe that their use never really took a foothold because the company (Addition Technology, Inc.) simply could not afford to compete with the national and international marketing efforts by manufacturers of excimer lasers for LASIK as well as physicians practices for LASIK.  Even though many EyeMDs initially trained to provide Intacs inserts, relatively few ever surgically implanted them.  The technology is good and it is fully reversible for the relatively few individuals who choose this technology as a refractive procedure. 

Today, I believe the main use of f Intacs prescription inserts is for keratoconus patients who are unable to achieve the vision they desire through glasses or contact lenses and who would otherwise be left only with the therapeutic option of corneal transplantation.  In this situation, a substantial number of patients might benefit from placement of Intacs prescription inserts. 

To find an EyeMD who implants Intacs prescription inserts, visit Addition Technology’s website, www.getintacs.com.