PURPOSE: Intrastromal corneal ring segments (Intacs) were inserted in four eyes with iatrogenic keratectasia, 12 to 44 months after laser in situ keratomileusis (LASEK) in two patients and photorefractive keratectomy (PRK) in two patients, in order to avoid penetrating keratoplasty and to improve quality of vision. METHODS: A modified asymmetrical Intacs micro-thin prescription inserts implantation technique was used in three eyes where a 1.0-mm temporal incision and a superior-inferior dissection were performed A thicker segment was implanted in the lower stromal channel and a thinner one was placed in the superior channel. In the fourth eye, because of the severity of the corneal bulging after PRK, two 5.0-mm optical zone symmetrical Ferrara Ring segments were implanted. RESULTS: len months after surgery, all eyes experienced a significant improvement of uncorrected and best spectacle-corrected visual acuity. The topographical indices showed an overall surface régularisation with increased corneal uniformity and potential corneal visual acuity. No intraoperative or postoperative complications occurred. CONCLUSIONS: Asymmetrical or symmetrical corneal ring segment implantation in eyes with keratectasia after LASIK or PRK resulted in safe, fairly predictable corneal regularization, with significant improvement of aided and unaided vision. In the short term, these techniques seem to be helpful in reducing the progression of corneal ectasia after excimer laser surgery, delaying or avoiding the need of penetrating keratoplasty. [J Refract Surg 2002;18:535-541]

The intrastromal corneal ring (ICR) is a refractive device with the potential to correct both myopia and hyperopia. The ring is inserted in the peripheral corneal stroma at about two-thirds depth. Mechanical expansion of the ring flattens the central cornea, while constriction of the ring steepens it. Two rabbits underwent ICR surgery. The rabbit with ring expansion showed central corneal flattening 6 months postoperatively. The rabbit with ring constriction showed central corneal steepening 6 months postoperatively. In both cases, the central cornea remained clear.

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PURPOSE: Intrastromal corneal ring segments (ICRS; Intacs) were inserted in a patient with residual myopia of -3.375 D (spherical equivalent) 10 months after laser in situ keratomileusis (LASIK). METHODS: A standard intrastromal corneal ring segment implantation technique was used with the addition of intraoperative ultrasonic pachymetry in 4 quadrants at the 7-mm zone to insure adequate stromal thickness for segment insertion. RESULTS: Four months after ICRS surgery and 14 months after LASIK, the patient had uncorrected visual acuity of 20/20 and a cycloplegic refraction of piano -1.00 ? 23°. CONCLUSION: Implantation of intrastromal corneal ring segments in an eye with previous LASIK resulted in additional corneal flattening with a decrease in residual myopia and improved uncorrected visual acuity. [J Refract Surg 2000;16:365-367]