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Swarupa Kancherla, Ian P Conner, Leon C Ho, Seong-Gi Kim, Gadi Wollstein, Joel S Schuman, Kevin C Chan; Relationships between Anterior Visual Pathway Morphology, Ocular Physiology and Visual Function in Glaucoma. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5847.
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Glaucoma involves neurodegenerative damage and may benefit from intervention if detected early. Both intraocular pressure (IOP) and cerebrospinal fluid (CSF) pressure may play a role in glaucoma pathogenesis, but the inter-relationships between current structural, physiological and functional parameters for assessing glaucoma remain controversial. This study used MRI and OCT to evaluate morphology of the anterior visual pathway in association with IOP and visual field (VF) function in glaucoma.
8 early glaucoma (age=63.3±7.6 yrs), 9 advanced glaucoma (age=65.7±8.5 yrs) and 7 healthy control subjects (age=64.1±8.4 yrs) underwent whole-brain T1-weighted imaging without orbital fat suppression but with CSF signal suppression in subarachnoid space (SAS) via 3-Tesla MRI scanner. Cross-sectional areas of optic nerve (ON), SAS, ON sheath (ON+SAS) and optic chiasm (OC) were measured. Spectral-domain OCT of peripapillary retinal nerve fiber layer (pRNFL) thickness, macular ganglion cell complex (GCC) thickness and cup-to-disc ratio (c/d), Humphrey visual field of pattern standard deviation (PSD), mean deviation (MD) and VF index (VFI), and IOP were collected clinically. ANOVA, post-hoc Tukey’s tests and correlation tests were performed across the 3 groups.
ANOVA and post-hoc Tukey’s tests show significant thinning of retinal layers (pRNFL and GCC), ON head cupping (c/d), atrophy of ON and OC (MRI), and visual field deficits (PSD, MD and VFI) in advanced glaucoma compared to control (p<0.05). Such pathological changes remained significant for pRNFL, GCC, OC area, PSD, MD and VFI when comparing advanced to early glaucoma, whereas only c/d showed significant difference between early glaucoma and control. No difference in SAS, SAS+ON, IOP or age was found among 3 subject groups (p>0.05). In Table 1, structural MRI in ON and SAS appeared to correlate better with retinal OCT than VF function. While SAS size has been suggested to reflect CSF pressure, IOP was not related to SAS but was correlated to ON morphology (ON area and c/d) with marginal significance.
ON and OC areas appear to be more sensitive MRI markers than SAS or SAS+ON in evaluating optic neuropathy and its relations to retinal morphology in glaucoma. OCT showed stronger structure-function correlations than MRI with VF parameters.
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