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J Cataract Refract Surg. 2010 Sep;36(9):1562-72. doi: 10.1016/j.jcrs.2010.04.029.

Modification and refinement of astigmatism in keratoconic eyes with intrastromal corneal ring segments.

Author information

1
Keratoconus Unit, Vissum Corporation, and Departamento de Optica, Farmacología y Anatomía, Universidad de Alicante, Alicanted, Spain.

Abstract

PURPOSE:

To analyze corneal astigmatic changes after implantation of intrastromal corneal ring segments (ICRS) in keratoconic eyes using the Alpins vectorial method.

SETTING:

Vissum Corporation, Alicante, Spain.

METHODS:

Keraring ICRS were implanted in eyes with a diagnosis of keratoconus. One of 3 surgeons performed the ICRS implantations using femtosecond technology and following the same protocol. Visual, refractive, keratometric, and corneal aberrometric changes were evaluated during a 12-month follow-up. Corneal astigmatic changes were also analyzed using the following Alpins vectorial components: targeted induced astigmatism (TIA), surgically induced astigmatism (SIA), difference vector, magnitude of error, flattening effect, and torque.

RESULTS:

Postoperatively, there was significant visual improvement (P = .03), significant central flattening (P = .03), and a significant reduction in manifest astigmatism (P<.01). The magnitude of SIA vector was significantly lower than the TIA postoperatively (P>or=.02). The mean magnitude of the difference vector 3 months postoperatively was +2.96 diopters (D) +/- 1.68 (SD). The mean magnitude of error remained negative and unchanged (P>or=.10). The mean magnitude of the flattening effect was significantly lower than the TIA at all postoperative visits (P<or=.01). The mean magnitude of torque vector was 1.21 +/- 0.98 D at 3 months. Significant negative correlations were found between preoperative corneal astigmatism and the magnitude of error and difference vector at all postoperative visits.

CONCLUSION:

Although ICRS implantation significantly reduced the magnitude of corneal astigmatism, there was a trend toward undercorrection and the meridian of correction was not appropriate in all cases, showing the need for nomogram adjustments.

PMID:
20692571
DOI:
10.1016/j.jcrs.2010.04.029
[Indexed for MEDLINE]
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