Intacs use reviewed for complications

Long-term use should be followed for complications.

PORTLAND, U.S.A. — A review of premarket approval data for the Intacs intrastromal corneal ring segment (KeraVision; Fremont, U.S.A.) system highlighted the complications and concerns of surgeons adopting this procedure into their practices.

Larry F. Rich, MD, examined the data during his presentation at the American Academy of Ophthalmology Refractive Surgery Subspecialty Day held in Orlando, U.S.A.

Advantages and disadvantages exist with any operation or device, Dr. Rich said. Intacs offer an alternative to the existing laser surgery. Also, the procedure spares the central cornea, retains the cornea’s prolate geometry and offers a potentially rapid return to preoperative vision.

Disadvantages include the fact that Intacs do not expand the treatment range offered by excimer procedures. Intacs received U.S. Food and Drug Administration (FDA) approval for between 1 D and 3 D with less than 1 D of astigmatism. Other procedures cover this range of correction, Dr. Rich said.

Because the treatment range is narrow and requires less than 1 D of astigmatism, surgeons must ensure that they have conducted the proper refraction and pachymetry. The best use may be in low myopes with early presbyopia.

Surgeons in the United States have reported on Intacs implanted for more than 8 years without erosion. More than 1,200 eyes were included in the three-phase FDA trials.

“Results that we have so far from the implantation are 8 years out, and longer-term risks are not known,” he said. “We do not know, for example, whether these will be retained in the cornea in the long term,” although, according to Dr. Rich, it is known from nearly 50 years of experience that PMMA is well-tolerated in the eye

Channel haze seen

Complications with the Intacs are rare, but they do exist, Dr. Rich said.

In the premarket approval study for KeraVision, one anterior chamber perforation occurred and the Intacs were not implanted. There were three corneal surface perforations that precluded implantation, as well.

One subconjunctival chemosis developed, presumably as an allergic response to the prep solution. In this case, Intacs were not placed because the suction could not be applied.

Small hemorrhages occurred that did not prevent implantation. And postoperatively, potential and real problems exist with the epithelium, Dr. Rich said.

Implantation requires an incision in the stroma with a diamond knife in a radial orientation. This incision site is healed usually by 3 days, but it can produce inclusion cysts inside the wound in about 30% of cases. In 20% of the cases presented to the FDA, these inclusion cysts persisted. In one case, the inclusion cyst had to be removed. However, Dr. Rich said, these were “not clinically significant problems.”

Stromal thinning occurred in one of 449 cases. It probably resulted from shallow placement, but this could have led to an anterior stromal melt if the Intacs were not removed.

Postoperatively, problems occurred with the corneal stroma. Dr. Rich said that almost every patient developed tunnel haze or channel haze. This stemmed from a disruption of the transparent lamellar matrix by the dissector.

The haze can be easily seen at 1 day postoperatively, but then builds up in the subsequent weeks to months and progresses to a gray, translucent haze. Yet it does not usually cause symptoms or problems.

“Deposits in the tunnel are perhaps due to the attempt by the cornea to fill in these spaces,” Dr. Rich said. “It’s usually, again, not seen until weeks or months postoperatively. And these can be white, gray, tan, chalky or translucent. And, again, this does not usually cause symptoms or problems.”

Ramifications

Corneal stroma complications include one infection in the implant site, or less than 1% of cases, which is equivalent to other refractive procedures. The infection resulted in the Intacs being explanted. The patient was treated appropriately with antibiotics and the infection resolved and returned to best corrected preoperative acuity.

Other studies outside of the United States have revealed infections as well, he said.

Anterior chamber complications included perforation or anterior chamber reactions. Anterior chamber reactions in one study were shown to be less with an Intacs than it was with laser in situ keratomileusis.

Intacs have induced astigmatism of more than 1 D in 20% of eyes. There has been a transient decreased sensation of the cornea, but this usually recovers after about 3 months.

Visual disturbances have led patients to ask for removal.

Night vision fluctuations occurred in 2.9% of cases. These stemmed from glare from lights coming from the side instead of straight ahead. Diplopia occurred in 1.6% of patients, glare in 1.3% and halos in 1.3%.

In terms of stability, 3% had a change of refractive error of more than 1 D between 3 and 24 months postoperatively.

The explantation rate was 2% in phase 2. One case involved an anterior chamber perforation and one case involved infiltrative keratitis. In phase 3, about 7% (31 of 449) were explanted due to glare, halos, improper correction, infection and miscellaneous personal reasons.

“We have a relatively new technology,” Dr. Rich said. “We don’t have a great number of complications, and they don’t seem to be very severe. With time, we’ll have a better idea of where this is going and how long these will be retained in the eye.”


Tunnel haze. Grade 1: Mild loss of stromal transparency.	Tunnel deposits. Grade 3: Moderate, more confluent. Iris detail barely visible.

Epithelial cyst or plug in incision. Grade 2: gape with cysts.

Tunnel haze. Grade 4: Heavy loss of transparency, no iris detail visible.	Tunnel deposits. Grade 1: Isolated deposits.

Tunnel deposits. Grade 4: Fully confluent. Iris detail not visible.	Infiltrates.

For Your Information:

Larry F. Rich, MD, can be reached at 3375 W.W. Terwilliger Blvd., Portland, OR 97201 U.S.A.; +(1) 503-494-7674; fax: +(1) 503-494-3929. Dr. Rich has no direct financial interest in any of the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

KeraVision Inc. can be reached at 48360 Milmont Drive, Fremont, CA 94538 U.S.A.; +(1) 510-353-3000; fax: +(1) 510-353-3030.

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