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Rafael L Furlanetto, Sergio H. Teixeira, Maria Angela M. Barreiros, Edson Amaro, Augusto Paranhos; POSITIVE CORRELATION OF THE OPTIC NERVE DIFFUSION TENSOR IMAGING WITH THE ASYMMETRY OF OCULAR STRUCTURAL DAMAGE IN GLAUCOMA, BUT NOT WITH FUNCTIONAL DAMAGE ASYMMETRY. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4580. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate whether an asymmetry index derived from the fractional anisotropy (FA) of the optic nerves measured by 3-Tesla magnetic resonance (MR) diffusion tensor imaging (DTI) were correlated with the level of asymmetry of ocular structural or functional glaucomatous damage.
This was a prospective cross-sectional study that included glaucoma patients with a wide range of structural and functional damage, and age-matched healthy subjects. All participants performed SITA-standard 24-2 automated perimetry (SAP) and frequency doubling perimetry (FDT) (functional tests), optic disc stereophotograph and spectral-domain optical coherence tomography (OCT) (structural tests), and 3-Tesla MR DTI. FA, which is a DTI-derided index, was measured at each optic nerve. Fractional Anisotropy Asymmetry Index (FAAI) was calculated as the absolute difference between both FA of the same individual. Generalized Estimating Equations and Pearson’s correlation were used in statistical analysis.
We included 53 subjects (41 glaucoma patients and 12 healthy volunteers), of which 56.86% were women. Mean age was 62.9 ± 0.7 years in glaucoma and 62.3 ± 6.2 years in control groups (p=0.9). Average SAP Mean Deviation (MD) was -14.09±1.5 dB in right eye and 16.69±1.6 dB in left eye of glaucoma patients. In glaucoma group, there was a positive significant correlation between FAAI and OCT average cup-to-disc ratio and vertical cup-to-disc ratio asymmetry (R2= 0.105, p= 0.04; and R2= 0.131, p= 0.02; respectively), but FAAI was not correlated with the inter-eye retinal nerve fiber layer thickness difference (p= 0.48) or asymmetry indices of functional parameters (all p>0.05).
FAAI was positively correlated with the level of ocular structural damage asymmetry in glaucoma measured by OCT, but not with functional damage. This indicates that FAAI may be a surrogate measure of the level of the inter-eye structural damage asymmetry in glaucoma. Thus, our study suggests that DTI may be also used to evaluate the level of asymmetry of glaucomatous damage.
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