Alteration of Fractional Anisotropy and Mean Diffusivity in Glaucoma: Novel Results of a Meta-Analysis of Diffusion Tensor Imaging Studies

<div><p>Objectives</p><p>We hypothesized that a meta-analysis of existing studies may help to reveal significant changes on diffusion tensor imaging (DTI) in patients with glaucoma. Therefore, a meta-analysis was utilized to investigate the possibility that DTI can detect white matter damage in patients with glaucoma.</p><p>Methods</p><p>The study design and report adhered to the PRISMA Statement guidelines. DTI studies that compared glaucoma patients and controls were surveyed using PubMed, Web of Science and EMBASE (January 2008 to September 2013). Stata was used to analyze the decrease in fractional anisotropy (FA) and increase in mean diffusivity (MD) in the optic nerve and optic radiation in patients with glaucoma.</p><p>Results</p><p>Eleven DTI studies were identified through a comprehensive literature search, and 10 independent DTI studies of glaucoma patients were eligible for the meta-analysis. A random effects model revealed a significant FA reduction in the optic nerve and optic radiation, as well as a significant MD increase in the tracts. A heterogeneity analysis suggested that FA may be related to glaucoma severity.</p><p>Conclusions</p><p>Our findings revealed that the optic nerve and optic radiation were vulnerable regions in patients with glaucoma and that FA may be correlated with glaucoma severity and age. Furthermore, this study suggests that magnetic resonance imaging in patients with glaucoma may help to provide objective evidence to aid in the diagnosis and management of glaucoma.</p></div

Meta-analysis results of FA in the optic nerve and optic radiation in patients with glaucoma compared with controls (data from Table 2).

<p>There is an apparent trend toward high heterogeneity (P<0.05, and the diamond shape meaning significant difference appears on the left side;I²>50%). FA: fractional anisotropy; SMD: standardized mean difference; CI: confidence interval.</p

Results of an FA analysis with respect to age in the optic nerve of patients with glaucoma compared with controls.

<p>There is an apparent difference between three age groups (a: age 21–54 years, b: age 54.8–59 years, and c: mean age 60–69 years). We can conclude that there was deceasing FA of the optic nerve with increasing age in patients with glaucoma (P<0.05 and the diamond shape appears on the left side). FA: fractional anisotropy; SMD: standardized mean difference; CI: confidence interval.</p

Process of study selection.

<p>Process of study selection.</p

MOESM1 of Microbial community and diversity in the feces of Sichuan takin (Budorcas taxicolor tibetana) as revealed by Illumina Miseq sequencing and quantitative real-time PCR

Additional file 1: Table S1. Primers used for group-specific quantitative real-time PCR

Results of an FA analysis with respect to glaucoma severity in the optic nerve (a) and optic radiation (b) of patients with glaucoma compared with controls.

<p>There is an apparent difference between two severity stage groups (a: all stages, b: severe stage). We can conclude that there was decreasing FA of the optic nerve with increasing glaucoma severity (P<0.05, and the diamond shape appears on the left side). FA: fractional anisotropy; SMD: standardized mean difference; CI: confidence interval.</p

Meta-analysis results of MD in the optic tracts and optic radiation of patients with glaucoma compared with controls (data from Table 3).

<p>A significant difference between patients and controls was revealed, with high heterogeneity (P<0.05 and the diamond shape appears on the right side; I²>50%). MD: mean diffusivity; SMD: standardized mean difference; CI: confidence interval.</p

Results of an FA analysis with respect to age in optic radiation of patients with glaucoma compared with controls.

<p>There is an apparent difference between two age groups (a: age 21–54 years, b: age 54.8–59 years). We can conclude that there was decreasing FA of the optic radiation with increasing age in patients with glaucoma (P<0.05, and the diamond shape appears on the left side). FA: fractional anisotropy; SMD: standardized mean difference; CI: confidence interval.</p

Brain FA map derived from the region of interest analysis: (a) optic nerve, (b) optic radiation.

<p>We set the full width half maximum (FWHM) as 30.</p

Information statistics: on the mean and standard deviation of the FA in the optic nerve and optic radiation.

<p>FA: fractional anisotropy; SD: standard deviation.</p