Abstract
Ocular hypertension (OHT), the common situation in adult patients in the outpatients, occurs ∼5% worldwide. However, there are still some practical problems in differentiation of OHT with early primary open-angle glaucoma (POAG) using current standard methods. Application of high resolution diffusion tensor imaging (DTI) enables us to the differentiate axonal architecture of visual pathway between POAG and OHT subjects. Among 32 POAG patients recruited (15 OHT and 14 control subjects), 62.5% of glaucoma were in early stage for the current study. All subjects underwent ophthalmological assessments with standard automated perimetry and optical coherence tomography (OCT). DTI was applied to measure fraction anisotropy (FA) and mean diffusivity (MD) of optic tract (OT), lateral geniculate body (LGN) and optic radiation (OR) using voxel-based analysis. Our data demonstrated that FA values of bilateral OR in POAG were significantly lower in the right or left than that of OHT patients (left OR: 0.51 ± 0.04 vs. 0.54 ± 0.03, p < 0.05; right OR: 0.51 ± 0.05 vs. 0.54 ± 0.03, p < 0.05). In right LGN, MD values were higher in POAG patients compared with OHT subjects (9.81 ± 1.45 vs. 8.23 ± 0.62, p < 0.05). However, no significant difference of all of the DTI parameters was observed between OHT and control subjects. DTI parameters in POAG patients were positively correlated with morphological and functional measurements (p < 0.05). Vertical cup to disc ratio (VCDR) was correlated with ipsilateral FA of OT (p < 0.05), ipsilateral MD of OT (p < 0.05), ipsilateral MD of LGN (p < 0.05), and contralateral MD of OT (p < 0.05). Mean deviation of visual field (MDVF) was correlated with ipsilateral FA of OT (p < 0.05), ipsilateral MD of OT (p < 0.05), and ipsilateral FA of LGN (p < 0.05). Our study demonstrated that DTI can differentiate POAG from OHT subjects in optic pathway, particularly in early POAG, and DTI parameters can quantify the progression of POAG.
Highlights
Glaucoma, very common condition with approximately 79.6 million cases of blindness worldwide (Quigley and Broman, 2006), is rapidly increasing in the near future
In the current study, according to Hodapp-Parrish-Anderson classification, there was 62.5, 25, or 12.5% of glaucoma patients were in early, moderate stage, or advanced stage, respectively
fraction anisotropy (FA) values of bilateral optic radiation (OR) in primary open-angle glaucoma (POAG) patients were significantly lower; mean diffusivity (MD) values of POAG patients were higher in bilateral lateral geniculate body (LGN) and in left optic tract (OT) (12.11 ± 1.69 vs. 10.38 ± 1.85, p < 0.05)
Summary
Very common condition with approximately 79.6 million cases of blindness worldwide (Quigley and Broman, 2006), is rapidly increasing in the near future. Glaucoma is the name for a group of visual disorders which are characterized by the progressive loss of retinal ganglion cells (RGCs) and the degeneration of the optic nerve. Such changes lead to the progression of typical morphometric alterations that involve the optic nerve damages as well as visual field (VF) loss. Primary open-angle glaucoma (POAG) is the most prevalent type of glaucoma in the world (Weinreb and Khaw, 2004), which has a feature of progressive of optic nerve damage and loss of RGCs. there is a good correlation between high intraocular pressure (IOP) and the progression of POAG, its precise underlying pathophysiology is still unclear. OHT is essentially different from POAG because of no RGCs damage
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