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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]

Significantly better predictability of postoperative vault height was achieved by including sulcus diameter into the ICL sizing formula compared with using the traditional white-to-white-based formula.

This study suggests that the internal geometry of the anterior segment of human eyes does not constitute a circle. This may have significant relevance for the accurate sizing of phakic intraocular lenses.

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