[Clinical and histological studies on the intrastromal corneal ring segments (ICRS(R), Intacs(R))].

Intrastromal corneal ring segments (ICRS(R), Intacs(R)) are corneal inlays made of PMMA with an arc length of 150 degrees for the correction of low to moderate myopia. This additive and potentially reversible method has recently been developed to clinical usefulness during the last few years. Besides the historical development und the results of the US FDA studies, we focus on the results of the European experience with this technique. For the first time, long-time follow-up results (5 years from a single surgical center) are presented. Morphological changes after implantation of Intacs(R) were investigated in a series of patients by confocal microscopy. Weeks and months after implantation "lamellar channel deposits" regularly appear around the segments. This material consists of intracellular lipids (cholesterol ester, triglyceride and unesterified cholesterol), as we could show in new histological studies on rabbit eyes. New developments of this technique include short arc length segments (130 degrees ) for the correction of myopia concurrent with astigmatism and radially placed corneal inlays (Intrastromal Corneal Segments, ICS(R)) for the correction of hyperopia. In recent years, Intacs(R) have also been implanted in eyes with keratoconus and keratectasia after LASIK. These early results seem to indicate that in certain cases of early keratoconus, these implants can indeed improve corneal geometry and vision. Even in cases of regression or undercorrection after LASIK (with thin corneas), Intacs(R) seem to give promising results in selected cases. Although Intacs(R) do give comparable results regarding both safety and efficacy when compared with PRK and LASIK, this technology has not yet been widely accepted among refractive surgeons. Whether Intacs(R) will play a greater role in routine refractive surgery in the future or will just remain a special device for the correction of keratectasia, keratoconus or regression after LASIK cannot yet be decided with certainty.