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Magnetic resonance in studies of glaucoma.

Fiedorowicz M, Dyda W, Rejdak R, Grieb P - Med. Sci. Monit. (2011)

Bottom Line: These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density.Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye.Further applications of MR techniques in studies of glaucomatous brains are indicated.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pharmacology, Polish Academy of Science Medical Research Centre, Warsaw, Poland. mfied@cmdik.pan.pl

ABSTRACT
Glaucoma is the second leading cause of blindness. It affects retinal ganglion cells and the optic nerve. However, there is emerging evidence that glaucoma also affects other components of the visual pathway and visual cortex. There is a need to employ new methods of in vivo brain evaluation to characterize these changes. Magnetic resonance (MR) techniques are well suited for this purpose. We review data on the MR evaluation of the visual pathway and the use of MR techniques in the study of glaucoma, both in humans and in animal models. These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density. Studies on rats employing manganese-enhanced MRI showed that axonal transport in the optic nerve is affected. Diffusion tensor MRI revealed signs of degeneration of the optic pathway. Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye. Magnetic resonance spectroscopy demonstrated changes in metabolite levels in the visual cortex in a rat model of glaucoma, although not in glaucoma patients. Further applications of MR techniques in studies of glaucomatous brains are indicated.

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Graphs illustrate DT MR imaging–derived (A) mean MD (mMD) and (B) mean FA (mFA) values for optic nerves correlated with no glaucoma (control) and different stages of glaucoma. Median values (horizontal line inside box), ranges, and interquartile ranges are shown. Whiskers extending from each end of the boxes indicate minimal and maximal values. Reprinted from Garaci et al. [41]. Copyright (2009), with permission from Radiological Society of North America.
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f2-medscimonit-17-10-ra227: Graphs illustrate DT MR imaging–derived (A) mean MD (mMD) and (B) mean FA (mFA) values for optic nerves correlated with no glaucoma (control) and different stages of glaucoma. Median values (horizontal line inside box), ranges, and interquartile ranges are shown. Whiskers extending from each end of the boxes indicate minimal and maximal values. Reprinted from Garaci et al. [41]. Copyright (2009), with permission from Radiological Society of North America.

Mentions: Hui et al. [40], using DT MRI, showed that in a rat model of ocular hypertension induced by laser photocoagulation of the episcleral and limbal veins, DT MRI-derived parameters (ie, radial diffusivity and fractional anisotropy) were affected in the optic nerve. Radial diffusivity was increased and fractional anisotropy decreased, suggesting that axonal density was reduced by around 10% when compared to control rats. Moreover, the authors performed DT MRI at various time points after photocoagulation and showed that radial diffusivity was increasing and fractional anisotropy was decreasing over time. These results were confirmed by histological evaluation of the optic nerve. Garaci et al. [41] reported similar findings in patients with POAG. Mean diffusivity was increased and correlated with the stage of glaucomatous optic neuropathy, while fractional anisotropy was decreased and also correlated with the stage of glaucoma (Figure 2).


Magnetic resonance in studies of glaucoma.

Fiedorowicz M, Dyda W, Rejdak R, Grieb P - Med. Sci. Monit. (2011)

Graphs illustrate DT MR imaging–derived (A) mean MD (mMD) and (B) mean FA (mFA) values for optic nerves correlated with no glaucoma (control) and different stages of glaucoma. Median values (horizontal line inside box), ranges, and interquartile ranges are shown. Whiskers extending from each end of the boxes indicate minimal and maximal values. Reprinted from Garaci et al. [41]. Copyright (2009), with permission from Radiological Society of North America.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3539477&req=5

f2-medscimonit-17-10-ra227: Graphs illustrate DT MR imaging–derived (A) mean MD (mMD) and (B) mean FA (mFA) values for optic nerves correlated with no glaucoma (control) and different stages of glaucoma. Median values (horizontal line inside box), ranges, and interquartile ranges are shown. Whiskers extending from each end of the boxes indicate minimal and maximal values. Reprinted from Garaci et al. [41]. Copyright (2009), with permission from Radiological Society of North America.
Mentions: Hui et al. [40], using DT MRI, showed that in a rat model of ocular hypertension induced by laser photocoagulation of the episcleral and limbal veins, DT MRI-derived parameters (ie, radial diffusivity and fractional anisotropy) were affected in the optic nerve. Radial diffusivity was increased and fractional anisotropy decreased, suggesting that axonal density was reduced by around 10% when compared to control rats. Moreover, the authors performed DT MRI at various time points after photocoagulation and showed that radial diffusivity was increasing and fractional anisotropy was decreasing over time. These results were confirmed by histological evaluation of the optic nerve. Garaci et al. [41] reported similar findings in patients with POAG. Mean diffusivity was increased and correlated with the stage of glaucomatous optic neuropathy, while fractional anisotropy was decreased and also correlated with the stage of glaucoma (Figure 2).

Bottom Line: These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density.Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye.Further applications of MR techniques in studies of glaucomatous brains are indicated.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Pharmacology, Polish Academy of Science Medical Research Centre, Warsaw, Poland. mfied@cmdik.pan.pl

ABSTRACT
Glaucoma is the second leading cause of blindness. It affects retinal ganglion cells and the optic nerve. However, there is emerging evidence that glaucoma also affects other components of the visual pathway and visual cortex. There is a need to employ new methods of in vivo brain evaluation to characterize these changes. Magnetic resonance (MR) techniques are well suited for this purpose. We review data on the MR evaluation of the visual pathway and the use of MR techniques in the study of glaucoma, both in humans and in animal models. These studies demonstrated decreases in optic nerve diameter, localized white matter loss and decrease in visual cortex density. Studies on rats employing manganese-enhanced MRI showed that axonal transport in the optic nerve is affected. Diffusion tensor MRI revealed signs of degeneration of the optic pathway. Functional MRI showed decreased response of the visual cortex after stimulation of the glaucomatous eye. Magnetic resonance spectroscopy demonstrated changes in metabolite levels in the visual cortex in a rat model of glaucoma, although not in glaucoma patients. Further applications of MR techniques in studies of glaucomatous brains are indicated.

Show MeSH
Related in: MedlinePlus