A 63-Year-Old Woman With Decreased Vision

Rod Foroozan, MD

Disclosures

April 03, 2018

Discussion

This patient developed decreased vision in the right eye with findings suggestive of glaucoma, including asymmetric IOP, cupping of the optic disc out of proportion to pallor, visual field loss conforming to the area of optic disc cupping, and retention of central visual function.

Normal tension glaucoma (NTG) may cause vision loss that looks similar to that from other forms of glaucoma[1] but in the absence of IOPs typically considered to be elevated (>21 mm Hg). NTG occurs more commonly in Asian patients[2] and is more likely to cause visual field defects that are more dense and closer to fixation than typical open-angle glaucoma.[3]

Although the precise mechanisms causing NTG are not clear, some have suggested that these patients may be more sensitive to a given IOP or that there may be more emphasis on a vascular mechanism.

Accumulating evidence suggests that an increased gradient of pressure across the lamina cribrosa is important in NTG.[3] Impairment in cerebrospinal fluid (CSF) circulation and the subsequent development of a compartment syndrome has also been considered to contribute to optic neuropathy. Stagnation of CSF flow may result in the accumulation of toxins, which can contribute to optic nerve damage.

Despite the lack of clarity about the causes of vision loss from NTG, there is evidence that lowering the IOP is helpful in reducing the rate of vision loss.[3] As in typical open-angle glaucoma, a reduction of IOP remains the only proven method of treatment for NTG.

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