Corneal biomechanical measurements before and after laser in situ keratomileusis

Michael Chen, Nancy Lee, Nirit Bourla, D. Rex Hamilton

Research output: Contribution to journalArticle

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Abstract

Purpose: To study the correlation between corneal biomechanical properties and surgical parameters in myopic patients before and after laser in situ keratomileusis (LASIK). Setting: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. Methods: In 43 eyes of 43 patients, the Ocular Response Analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) before and 1 month after LASIK. Manifest refraction spherical equivalent (MRSE), preoperative central corneal thickness (CCT), flap thickness (FT), and ablation depth (AD) were also recorded. Changes in these parameters after LASIK were calculated and the correlations between the change in CH (ΔCH), change in CRF (ΔCRF) and the AD, change in MRSE (ΔMRSE), and CCT were examined. The relationship between ΔCRF and ΔMRSE was examined by linear regression analysis. Results: The preoperative mean CH and mean CRF (11.52 mm Hg ± 1.28 [SD] and 11.68 ± 1.40 mm Hg, respectively) were significantly higher than postoperative values (9.48 ± 1.24 mm Hg and 8.47 ± 1.53 mm Hg, respectively) (P<.0001). A higher attempted correction was correlated with a larger ΔCH and ΔCRF (AD, r = 0.47 and r = 0.65, respectively; ΔMRSE, r = 0.51 and r = 0.66, respectively). No correlation was found between ΔCH, ΔCRF, and preoperative CCT. Conclusions: Changes in CH and CRF after LASIK suggest alteration in corneal biomechanics correlating with attempted correction. The CRF parameter may be more useful than the CH parameter in assessing biomechanical changes resulting from LASIK.

Original languageEnglish (US)
Pages (from-to)1886-1891
Number of pages6
JournalJournal of Cataract and Refractive Surgery
Volume34
Issue number11
DOIs
StatePublished - Nov 1 2008

Fingerprint

Laser In Situ Keratomileusis
R Factors
Los Angeles
Intraocular Pressure
Biomechanical Phenomena
Linear Models
Lasers
Regression Analysis

All Science Journal Classification (ASJC) codes

  • Surgery
  • Ophthalmology
  • Sensory Systems

Cite this

Chen, Michael ; Lee, Nancy ; Bourla, Nirit ; Hamilton, D. Rex. / Corneal biomechanical measurements before and after laser in situ keratomileusis. In: Journal of Cataract and Refractive Surgery. 2008 ; Vol. 34, No. 11. pp. 1886-1891.
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abstract = "Purpose: To study the correlation between corneal biomechanical properties and surgical parameters in myopic patients before and after laser in situ keratomileusis (LASIK). Setting: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. Methods: In 43 eyes of 43 patients, the Ocular Response Analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) before and 1 month after LASIK. Manifest refraction spherical equivalent (MRSE), preoperative central corneal thickness (CCT), flap thickness (FT), and ablation depth (AD) were also recorded. Changes in these parameters after LASIK were calculated and the correlations between the change in CH (ΔCH), change in CRF (ΔCRF) and the AD, change in MRSE (ΔMRSE), and CCT were examined. The relationship between ΔCRF and ΔMRSE was examined by linear regression analysis. Results: The preoperative mean CH and mean CRF (11.52 mm Hg ± 1.28 [SD] and 11.68 ± 1.40 mm Hg, respectively) were significantly higher than postoperative values (9.48 ± 1.24 mm Hg and 8.47 ± 1.53 mm Hg, respectively) (P<.0001). A higher attempted correction was correlated with a larger ΔCH and ΔCRF (AD, r = 0.47 and r = 0.65, respectively; ΔMRSE, r = 0.51 and r = 0.66, respectively). No correlation was found between ΔCH, ΔCRF, and preoperative CCT. Conclusions: Changes in CH and CRF after LASIK suggest alteration in corneal biomechanics correlating with attempted correction. The CRF parameter may be more useful than the CH parameter in assessing biomechanical changes resulting from LASIK.",
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Corneal biomechanical measurements before and after laser in situ keratomileusis. / Chen, Michael; Lee, Nancy; Bourla, Nirit; Hamilton, D. Rex.

In: Journal of Cataract and Refractive Surgery, Vol. 34, No. 11, 01.11.2008, p. 1886-1891.

Research output: Contribution to journalArticle

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T1 - Corneal biomechanical measurements before and after laser in situ keratomileusis

AU - Chen, Michael

AU - Lee, Nancy

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N2 - Purpose: To study the correlation between corneal biomechanical properties and surgical parameters in myopic patients before and after laser in situ keratomileusis (LASIK). Setting: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. Methods: In 43 eyes of 43 patients, the Ocular Response Analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) before and 1 month after LASIK. Manifest refraction spherical equivalent (MRSE), preoperative central corneal thickness (CCT), flap thickness (FT), and ablation depth (AD) were also recorded. Changes in these parameters after LASIK were calculated and the correlations between the change in CH (ΔCH), change in CRF (ΔCRF) and the AD, change in MRSE (ΔMRSE), and CCT were examined. The relationship between ΔCRF and ΔMRSE was examined by linear regression analysis. Results: The preoperative mean CH and mean CRF (11.52 mm Hg ± 1.28 [SD] and 11.68 ± 1.40 mm Hg, respectively) were significantly higher than postoperative values (9.48 ± 1.24 mm Hg and 8.47 ± 1.53 mm Hg, respectively) (P<.0001). A higher attempted correction was correlated with a larger ΔCH and ΔCRF (AD, r = 0.47 and r = 0.65, respectively; ΔMRSE, r = 0.51 and r = 0.66, respectively). No correlation was found between ΔCH, ΔCRF, and preoperative CCT. Conclusions: Changes in CH and CRF after LASIK suggest alteration in corneal biomechanics correlating with attempted correction. The CRF parameter may be more useful than the CH parameter in assessing biomechanical changes resulting from LASIK.

AB - Purpose: To study the correlation between corneal biomechanical properties and surgical parameters in myopic patients before and after laser in situ keratomileusis (LASIK). Setting: UCLA Laser Refractive Center of the Jules Stein Eye Institute, Los Angeles, California, USA. Methods: In 43 eyes of 43 patients, the Ocular Response Analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann-correlated intraocular pressure (IOPg), and corneal-compensated IOP (IOPcc) before and 1 month after LASIK. Manifest refraction spherical equivalent (MRSE), preoperative central corneal thickness (CCT), flap thickness (FT), and ablation depth (AD) were also recorded. Changes in these parameters after LASIK were calculated and the correlations between the change in CH (ΔCH), change in CRF (ΔCRF) and the AD, change in MRSE (ΔMRSE), and CCT were examined. The relationship between ΔCRF and ΔMRSE was examined by linear regression analysis. Results: The preoperative mean CH and mean CRF (11.52 mm Hg ± 1.28 [SD] and 11.68 ± 1.40 mm Hg, respectively) were significantly higher than postoperative values (9.48 ± 1.24 mm Hg and 8.47 ± 1.53 mm Hg, respectively) (P<.0001). A higher attempted correction was correlated with a larger ΔCH and ΔCRF (AD, r = 0.47 and r = 0.65, respectively; ΔMRSE, r = 0.51 and r = 0.66, respectively). No correlation was found between ΔCH, ΔCRF, and preoperative CCT. Conclusions: Changes in CH and CRF after LASIK suggest alteration in corneal biomechanics correlating with attempted correction. The CRF parameter may be more useful than the CH parameter in assessing biomechanical changes resulting from LASIK.

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