Journal of cataract and refractive surgery · 2010
Modification and refinement of astigmatism in keratoconic eyes with intrastromal corneal ring segments.
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Piñero David P, Alió Jorge L, Teus Miguel A, Barraquer Rafael I, Michael Ralph, Jiménez Ramón
Аннотация
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.
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.