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D. Y. Leung, F. C. Li, C. C. Tham, R. P. Chan, J. M. Tong, D. S. Lam; Harmonic Components of Intraocular Pressure Pulse Wave and Visual Field Progression in Normal Tension Glaucoma. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1668.
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© ARVO (1962-2015); The Authors (2016-present)
To study the association between amplitudes of harmonic components of intraocular pressure (IOP) pulse waves and field progression, in patients with normal tension glaucoma (NTG).
NTG and field progression were defined according to the Collaborative NTG Study. One hundred and nine eyes from 109 NTG subjects underwent dynamic contour tonometry (DCT) and the IOP pulse wave curves were Fast-Fourier-transformed to derive the Spectral Index (SI), defined as ratio of amplitudes of 1st to 3rd harmonic. Previous studies have suggested a role for SI, applied to blood flow waveforms, to indicate impaired perfusion in ophthalmic and other arteries. Curves of good quality index (Q1 or Q2) on tonometer, with segments lasting at least 10 seconds (averaging 300 IOP data for each subject) were used. The primary outcome was the association between SI and progression. This was a cross-sectional analysis of a prospectively recruited cohort.[ClinicalTrials.gov Identifier: NCT00321386]
All patients were followed up for 36 months. On univariate analysis, a lower SI (p=0.019), higher amplitudes in 3rd, 4th, 6th, 9th, 11th and 12th harmonics (p values ranged 0.002-0.023), thinner central corneas (p=0.009), disc hemorrhage (p=0.004), presence of systemic hypertension (p=0.003), cerebrovascular accidents (CVA) (p=0.002), family history of glaucoma (p=0.029) were associated with field progression. On multivariate analysis, lower SI (1.83 in progressed group vs. 2.29 in stable group; odds ratio [OR] = 2.07/ unit reduction, 95% confidence interval [CI] = 1.07-3.98, p=0.030), and thinner central corneas (527.5 µm in progressed group vs. 549.4 µm in stable group; OR = 1.20/ 10 µm thinning, 95% CI = 1.04-1.37, p=0.013) were associated with progression.
Low SI may be an independent risk factor associated with field progression in our NTG cohort. Further studies are warranted.
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