Treating Keratoconus With Intacs Corneal Ring Segments

Evaluation of intrastromal lipid deposits after intacs implantation using in vivo confocal microscopy

PURPOSE

To assess the structure and location of intrastromal lipid deposits after implantation of Intacs by using in vivo confocal microscopy.

METHODS

Seven eyes of six patients were examined by in vivo confocal microscopy 5 years (n = 6) or 2 months (n = 1) after uncomplicated implantation of Intacs for the correction of mild myopia. Selected images from all corneal layers were qualitatively evaluated for structural changes, with special attention paid to areas surrounding the Intacs implants.

RESULTS

In the peripheral cornea of eyes examined 5 years after surgery, epithelial and endothelial cell layers appeared normal. Tandem scanning confocal microscopy showed stromal haze surrounding the implants in all eyes examined, but no keratocyte activation was seen. Reflective amorphous or crystalline structures consistent with lipid deposition were detected in all eyes with long-term implantation of Intacs. Deposits were localized to the inner and outer edges of Intacs segments and to the region anterior to the implant. Confocal microscopy did not show any deposits in the eye examined 2 months after surgery, although the region anterior to the implant appeared hazy and edematous. Areas central to the implant appeared normal in all eyes.

CONCLUSIONS

The mechanical and physiologic stresses introduced by the implantation of Intacs lead to the accumulation of lipid deposits in the extracellular matrix. By using in vivo confocal microscopy, the location and structure of these deposits can be determined.

Intacs adjustment surgery for keratoconus

PURPOSE

To describe the visual outcome of keratoconic eyes managed with Intacs (Addition Technology, Inc.) that required additional Intacs surgery (defined as any combination of removal, exchange, addition, or shifting of an Intacs segment).

SETTING

Private refractive surgery center, Jerusalem, Israel.

METHODS

This retrospective noncomparative interventional consecutive small case series studied all eyes of a cohort of 58 keratoconic eyes managed with Intacs that had additional Intacs surgery. The uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, manifest refraction, videokeratography, and patient questionnaires on visual function were assessed. These outcome measures were compared before Intacs implantation, before Intacs adjustment, and 1 year after the final Intacs adjustment. Eyes having any intervention other than Intacs surgery were excluded.

RESULTS

Of 58 keratoconic eyes managed with Intacs, 7 had additional Intacs surgery. After the initial Intacs surgery, 6 of these eyes had UCVA < or =20/100 and 1 had UCVA of 20/50. After the final Intacs adjustment, 3 eyes achieved UCVA > or =20/40, 5 achieved UCVA > or =20/70, and 2 remained <20/200. The indications for Intacs adjustments were increased astigmatism in 4 eyes, induced hyperopia (overcorrection) in 3, and undercorrection in 1. One eye had both surgically induced astigmatism and hyperopia. Induced astigmatism and hyperopia were most often managed by removing the superior segment. The undercorrected eye, having initially received a single inferior segment, was treated by implanting a superior segment.

CONCLUSIONS

Approximately 10% of keratoconic eyes managed with Intacs may require Intacs adjustment surgery, which often has a good outcome.

Comparison of single-segment and double-segment Intacs for keratoconus and post-LASIK ectasia

PURPOSE

To evaluate the efficacy of single-segment Intacs and compare with double-segment Intacs in subjects with post-LASIK ectasia and keratoconus.

DESIGN

Retrospective comparative analysis.

METHODS

setting: Boxer Wachler Vision Institute, Beverly Hills, California, USA. study population: Thirty-seven eyes of 28 patients with keratoconus and post-LASIK ectasia classified into two groups: single-segment group (17 eyes, 11 patients) and double-segment group (20 eyes, 17 patients). Both groups were matched for age, visual acuity (uncorrected, UCVA; best spectacle-corrected, BSCVA), refractive error (sphere, cylinder, spherical equivalent), and keratometry (K) value (flat, steep, average) by t test for equality of means. intervention: Single- or double-segment Intacs procedure with axis of incision for insertion in the steep axis of manifest refraction. main outcome measure: Improvement of acuity, refractive error, K values, and inferior-superior (I-S) ratio.

RESULTS

There was more improvement in UCVA in the single-segment group (nine lines) than the double-segment group (2.5 lines), P < .01; in BSCVA in the single-segment group (2.5 lines) than the double-segment group (<1 line), P < .01; in steep K values in the single-segment group (2.76 diopters +/- 2.68) than the double-segment group (0.93 diopters +/- 2.01), P = .02; and in I-S ratio in the single-segment group (9.51 +/- 7.49) than the double-segment group (4.22 +/- 4.82), P = .01; and greater cylinder decrease after Holladay vector analysis in the single-segment group (5.69 diopters +/- 3.10) than the double-segment group (1.58 diopters +/- 3.09), P < .01.

CONCLUSIONS

Single-segment Intacs improved both UCVA and BSCVA by differential flattening of inferior meridian and steepening of superior meridian as reflected by change in I-S ratio.

INTACS for keratoconus

BACKGROUND

INTACS are two, arc like, PMMA segments which were designed to be surgically inserted into the deep corneal stroma to flatten the central cornea. Their original application was for the refractive correction of mild myopia (−1 to −3D). However, because of the superior accuracy and familiarity with the excimer laser by refractive surgeons, they are rarely used for this indication, except in patients with forme fruste keratoconus or extremely thin corneas with less than 3D of Myopia (1,2).

Dr. Joseph Colin in France first conceived of the concept of using INTACS to treat patients with keratoconus and published his first report on the safety and efficacy for this indication in 2001(3). At 1 year, all 10 patients he operated became contact lens tolerant and demonstrated an improvement in both uncorrected and best-corrected acuity (4).

Since his pioneering work, corneal surgeons throughout the word have adopted this technology to treat patients with mild to moderate keratoconus who are contact lens intolerant and/or who desire a modest improvement in uncorrected and best-corrected visual acuity (5-14).

In the United States 0.25mm, 0.275mm, 0.30mm, 0.325mm and 0.35mm segments are available for use. They are approved in the United States by the FDA under an Human Devise Exemption for compassionate therapeutic use. Outside of the United States .40mm and 0.45mm sized segments are also available. Competitive devices the Ferrara ring and the Keraring are also sold and marketed outside of the United States since they do not have FDA approval in the USA. The main difference between these two devices is that with INTACS the optical zone is approximately 7mm while the Ferrara and Kerarings have an optical zone of the order of 4.5 to 5mm.

Recently Intacs SK was introduced outside of the United States. They have an optical zone of 6 mm and have a round design to minimize glare. They may be used to correct larger myopic and astigmatic refractive errors than INTACS because of their design and closer proximity to the visual axis(15)