Intacs Prescription Inserts Offer Effective Treatment for Keratoconus
BY C. BRADLEY BOWMAN, M.D.

Keratoconus is a disease of the cornea characterized by corneal thinning and steepening, which often produces poor vision due to irregular astigmatism. With the evolution of corneal topography and optical corneal mapping (Orbscan, Bausch & Lomb, Rochester, N.Y.), keratoconus and pellucid marginal degeneration are becoming more frequently diagnosed. Because of the irregular cornea, glasses often fail to correct vision, and rigid contact lenses become necessary for functional vision. Many patients become contact lens intolerant due to discomfort or because of the progression of their disease.

Traditionally, the only other treatment option beyond contact lenses has been corneal transplant surgery, which requires months of recovery and can lead to glaucoma and cataracts, and carries significant risk of infection and graft rejection. Intacs prescription inserts (Addition Technology, Inc., Sunnyvale, Calif.), approved by the FDA in August 2004, offer a minimally invasive alternative for keratoconus patients who are no longer able to wear contact lenses or glasses to correct their vision.

The benefits afforded by Intacs are substantial. The procedure is minimally invasive, it does not involve intraocular surgery and it is reversible. The goal of Intacs surgery is to reshape the cornea back to a point where either soft contacts or glasses can be worn, thus improving vision. In many patients, this sight-restoring procedure has prevented the need for the more invasive corneal transplant surgery.

In a 15-minute outpatient procedure, the tiny Intacs crescents are inserted into minute tunnels within the corneal stroma. Intacs naturally reshape the contour of the diseased cornea, making clear vision possible again. Whereas lasers and transplants remove tissue from the center of the cornea, Intacs, made of a medical polymer, add support and spare the removal of tissue from an already weakened cornea. If necessary, they can be adjusted or removed.

What Doctors Need to Know About the Procedure

► Doctors should be aware that their first few Intacs cases will be fairly challenging. Hand positions and instrument manipulations with this procedure are new and take some time to master. However, the learning curve is quick and doctors should feel very confident with the technique after about five cases.

► The most important aspect to the surgery technique is to make sure the Intacs inserts are placed at the appropriate depth. The most common complication for beginning surgeons is shallow placement, which will require removal to prevent extrusion or corneal surface problems. In order to ensure proper depth, set the diamond knife at 75% of incision-site pachymetry. Once the radial incision is made, it is critical to make sure that the pocketing hook and symmetric glide stay deep and maintain the lamellar dissection at the deepest point of the incision. As long as the initial pocket is made at the correct depth, a shallow displacement of the tunneling device is unlikely.

► Some have advocated using the IntraLaser femtosecond laser (IntraLase, Irvine, Calif.) to create the corneal tunnels for Intacs placement. Some doctors (myself included) prefer the "mechanical," or nonlaser, method because it preserves the lamellar corneal dissection and should provide for more consistent and reproducible results. Also, because the IntraLase places the tunnel at the same depth circumferentially around the cornea, there is the danger of deep perforation in areas of corneal thinning. Because the mechanical tunneling device creates a blunt lamellar dissection, entry into the anterior chamber is highly unlikely.

► Patients must have appropriate expectations. Many patients enter into the procedure thinking it will be like LASIK surgery and will give them 20/20 vision. Although a few patients will enjoy good uncorrected vision after Intacs, this is not the rule. The goal of this procedure is to prevent the need for corneal transplant surgery and hopefully get the patient out of hard contact lenses, allowing them to enjoy functional vision with either glasses or soft contact lenses. Patients also need to know that in some cases, Intacs may have no or very little effect.

► It is unknown whether this procedure will stabilize keratoconus progression. Patients need to be aware that their keratoconus may continue to progress, thus producing some instability in their vision.

► Many keratoconus patients have a history of chronic eye rubbing. It is critical that patients not rub their eyes after Intacs placements. Eye rubbing can cause migration of the inserts, resulting in complications.

A Case Study

Overview

It is important to note, as with all eye surgeries, Intacs is not for everyone. Contraindications include corneal scarring and corneal thinning. The cornea must be of adequate thickness to handle the inserts (at least 450 μm at the insert location). The following case study illustrates the ideal candidate.

A 29-year-old woman was referred to my practice by an optometrist for evaluation of her keratoconus. She was diagnosed with keratoconus more than 11 years ago, and over the past few months she had become increasingly intolerant of gas-permeable contact lenses.

The patient's vision was affecting her professional and personal life. As a sales engineer in the hospitality industry, she regularly makes presentations at trade shows and conferences. Her vision had become so impaired that she could not see the projected presentations she was giving and she had to memorize the information. On a personal level, her favorite hobby, motorcycle riding, became impossible because of her impaired vision.

Figure 1. Pre-op Orbscan of the OD and OS.

Initial Screening

The initial screening exam revealed UCVA of 20/400 and manifest refraction of -4.25 D, +2.5 D at 70, which produced 20/40 right eye. UCVA in the left eye was 20/300 with manifest refraction of -5.75 D, +3 D at 57, producing 20/40. A slit lamp examination revealed clear corneas, and no scarring or severe thinning in both eyes.

The Orbscan revealed classic keratoconus findings in both eyes with inferior steepening, central thinning and a steep posterior float. Maximum keratometry in the right eye was approximately 47 D. The left eye displayed more severe keratoconus, with maximum keratometry of 51 D (Figure 1).

The final assessment was moderate keratoconus in both eyes, with the left eye somewhat worse than the right. The patient had tried multiple gas-permeable rigid contact lenses and had become intolerant of the lenses. She reported that she could only wear the lenses about 4 to 6 hours each day.

All of these characteristics made the patient the ideal candidate for Intacs. The plan was to undergo Intacs surgery in the left eye first, and then the fellow eye later if the left was successful.

Surgery

Intacs surgery was performed in the left eye under topical sedation anesthesia, and 350-μm Intacs inserts were placed with the incision at a steep axis of 65Þ. The patient experienced no complications.

The first day postoperative, the patient reported improved vision and no pain. The UCVA was 20/60 and manifest refraction was -1.75 D + 0.75 D at 55 producing 20/30. A slit lamp examination revealed good depth and appropriate placement with minimal inflammation.

Two months postoperative, the patient reported continued vision improvement. In fact, the patient was functioning well without any vision correction (20/30) and requested surgery in her right eye.

Intacs surgery was performed on the right eye under topical sedation and 350-μm Intacs were placed with the incision at a steep axis of 80Þ.

	Figure 2. Post-op Orbscan of the OD and OS.

The first day postoperative, the patient reported no pain and improved vision. The UCVA was 20/40 and the examination showed good placement and a quiet eye.

Over 6 weeks later, the patient continued to report improving vision in both eyes. At 4 months after the initial surgery on the left eye, and 2 months after surgery on the right eye, her UCVA was 20/30 bilaterally. Manifest refraction revealed -025 D +0.75 x 075 OD, producing 20/25 vision, and -0.25 D +0.75 x 010 OS, producing 20/25.

Orbscan imaging in both eyes showed marked improvement with less inferior steepening and less irregular astigmatism (Figure 2).

Conclusion

For this patient, Intacs has been a life-changing procedure. She is now functioning well without contacts or eyeglasses. The Orbscan shows marked improvement in the cornea shape with corresponding corneal flattening and less irregular astigmatism. It is also important to note that medical insurance covered 90% of the patient's procedure. The patient is able to function better in her job and is back enjoying motorcycle riding.

As with many recently approved procedures, Intacs has yet to be covered by some insurance companies. Some third-party payers perceive Intacs as a sight-restoring refractive surgery. However, it is expected that insurance companies will find that Intacs will reduce the amount of money they spend on beneficiaries because it can prevent the need for costly corneal transplant surgery.

Intacs present an effective, minimally invasive outpatient solution for keratoconus patients and needs to be considered for keratoconus patients who have become contact lens intolerant.

C. Bradley Bowman, M.D., is with the Cornea Associates of Texas. Dr. Bowman has no financial interest in the information provided in this article. He can be reached via e-mail at bbowman598@aol.com.