Normal-Tension Glaucoma: A Glymphopathy?

Normal tension glaucoma as initial manifestation of Takayasu arteritis- an unknown entity

ObjectiveTo report an unusual manifestation of normal tension glaucoma(NTG) in a young female as presenting feature of Takayasu arteritis (TA).MethodsWe present a case of a 24-year-old woman who was initially diagnosed with NTG, with characteristic optic disc and retinal nerve fiber layer (RNFL) changes, and corresponding visual field defects. Further evaluation with CT angiography revealed that the patient had newly diagnosed TA.ResultsNTG was likely a manifestation of the underlying vasculitis. patient was initially started on oral prednisolone by the rheumatologist which was changed to steroid-sparing immunotherapy with methotrexate 15 mg once weekly and hydroxychloroquine 200 mg. The patient has been on regular follow-up for last one year with adequate IOP control and no progression of glaucomatous changes since presentation.ConclusionThis case highlights the importance of comprehensive ophthalmic evaluation in patients with NTG and the need to consider systemic conditions, such as TA, as potential underlying cause in young female patients presenting with NTG.

Glymphatic system impairment in normal tension glaucoma evaluated by diffusion tensor image analysis along the perivascular space

Disruption of the glymphatic system plays a vital role in pathogenesis of neurodegeneration in normal tension glaucoma (NTG). We evaluated the impairment of glymphatic system of NTG patients by diffusion tensor image analysis along the perivascular space (DTI-ALPS), and explored the correlation between the ALPS index and dysfunction of visual cortices in resting state. DTI-ALPS was applied to 37 normal controls (NCs) and 37 NTG patients. Multidirectional diffusivity maps and fractional anisotropy (FA) maps were reconstructed to calculate ALPS index. The Amplitude of low-frequency fluctuation (ALFF) in visual cortices (V1-V5) were calculated using resting-state fMRI. Clinical data and ALPS indexes were compared between the groups. Lateralization of ALPS indexes and differences in visual field of two eyes were analyzed. Subsequently, regression analyses between ALPS indexes and mean deviation (MD) values of bilateral eyes and ALFF of visual cortices were performed. The bilateral ALPS indexes of NTG patients decreased significantly. In NCs and NTG patients, ALPS indexes in right hemisphere were lower than that in left hemisphere. The right ALPS indexes of NTG patients were positively correlated with the MD values of the left eyes. In NTG patients, decreased ALFF was detected in right V1 and bilateral V2-5, and the left ALPS indexes were positively correlated with ALFF in bilateral V1, V2, V5, and right V3V area. The ALPS index decreased in NTG patients, correlated with visual defects and ALFF, indicating impairment of the glymphatic system and the potential to be a biomarker in the future.

Eye Movements and the Intraorbital Subarachnoid Space: Potential Contribution of Altered Cerebrospinal Fluid Pumping in Optic Neuropathies

Purpose

The optic nerve (ON) is mechanically perturbed by eye movements that shift cerebrospinal fluid (CSF) within its surrounding dural sheath. This study compared changes in ON length and CSF volume within the intraorbital ON sheath caused by eye movements in healthy subjects and patients with optic neuropathies.

Methods

Twenty-one healthy controls were compared with 11 patients having primary open angle glaucoma (POAG) at normal intraocular pressure (IOP), and 11 with chronic non-arteritic anterior ischemic optic neuropathy (NA-AION). High resolution magnetic resonance imaging (MRI) was performed in central and eccentric gazes, and analyzed to determine ON partial volume and gaze-related changes in ON path redundancy, ON elongation, and intrasheath CSF volume.

Results

ON volume was subnormal in both POAG and NA-AION. In all subjects, ON path redundancy decreased similarly from abduction to central gaze to adduction; in healthy subjects, the ON path was also significantly less redundant in infraduction and supraduction. The ON elongated significantly in adduction in controls and NA-AION but not in POAG. In all groups, CSF volume was 40 to 50 mm3 in central gaze, and significantly decreased in adduction, abduction, and supraduction in controls but subnormally in adduction only in POAG and NA-AION. The globe translated laterally more than normal in NA-AION but did not retract.

Conclusions

Horizontal gaze and supraduction change subarachnoid CSF volume around the retrobulbar ON. Eye movements might thus pump CSF to promote ON health, but this effect is subnormal in adduction in POAG and NA-AION, suggesting that retrobulbar CSF pumping is associated with chronic forms of these optic neuropathies.

Normal tension glaucoma following the treatment of normal pressure hydrocephalus

A man in his 70s developed progressive normal tension glaucoma following treatment for normal pressure hydrocephalus. This treatment included cerebrospinal fluid drainage and ventriculo-peritoneal shunt insertion to lower the intracranial pressure (ICP). Subsequent retinal nerve fibre layer thinning was visible on optical coherence tomography scans and was accompanied by corresponding glaucomatous visual field defects on perimetry. These changes occurred with normal intraocular pressure, indicating the patient had progressive normal tension glaucoma. The patient's ICP-lowering treatment for normal pressure hydrocephalus may, therefore, have contributed to his normal tension glaucoma, for which there is an emerging association.

Spaceflight associated neuro-ocular syndrome: connections with terrestrial eye and brain disorders

Spaceflight Associated Neuro-ocular Syndrome (SANS) is a series of findings found in astronauts who have experienced long-duration spaceflight. It is characterized by neuro-ocular changes that may irreversibly alter vision and increase the risk for the development of terrestrial eye and brain disorders. Theories regarding its etiology and countermeasures to combat the findings seen continue to evolve. There is currently no direct treatment for SANS. Traditional Chinese Medicine (TCM) modalities have been used to treat eye and brain disorders on Earth that are pathogenically similar to SANS, therefore, TCM may be able to target corresponding pathology in astronauts, prevent and mitigate SANS findings, and decrease the risk for future development of disorders. This paper intends to discuss pathological similarities between SANS and terrestrial eye and brain disorders and how TCM has been used to treat those disorders.

Normal-Tension Glaucoma and Potential Clinical Links to Alzheimer's Disease

Glaucoma is a group of optic neuropathies and the world's leading cause of irreversible blindness. Normal-tension glaucoma (NTG) is a subtype of glaucoma that is characterized by a typical pattern of peripheral retinal loss, in which the patient's intraocular pressure (IOP) is considered within the normal range (<21 mmHg). Currently, the only targetable risk factor for glaucoma is lowering IOP, and patients with NTG continue to experience visual field loss after IOP-lowering treatments. This demonstrates the need for a better understanding of the pathogenesis of NTG and underlying mechanisms leading to neurodegeneration. Recent studies have found significant connections between NTG and cerebral manifestations, suggesting NTG as a neurodegenerative disease beyond the eye. Gaining a better understanding of NTG can potentially provide new Alzheimer's Disease diagnostics capabilities. This review identifies the epidemiology, current biomarkers, altered fluid dynamics, and cerebral and ocular manifestations to examine connections and discrepancies between the mechanisms of NTG and Alzheimer's Disease.