Abstract
We examined the potential association of idiopathic normal pressure hydrocephalus (iNPH) with the generation of normal-tension glaucoma (NTG), to explore possible relationships between intracranial pressure (ICP) and the presence of glaucoma, and to compare disc morphology of NTG patients with or without iNPH. We investigated 20 iNPH patients, examined the prevalence of glaucoma, and compared the optic discs of NTG patients with iNPH (n = 11) and age-matched NTG patients without iNPH (n = 16). All data were collected prior to the treatment of iNPH, to eliminate the possibility that the treatment may have contributed to the progression of NTG. The diagnoses of NTG were made using visual field data, intraocular pressure measurements, fundoscopy, and optical coherence tomography (OCT). Using OCT, the optic nerve disc depth was also measured. The ICP was higher in the iNPH with NTG compared to iNPH without NTG (p = 0.0425), and the cupping depths of the discs of NTG patients with iNPH were significantly shallower compared with those of NTG patients without iNPH (p = 0.0097). Based on the difference in cupping depth, NTG patients with iNPH may have a different morphology from typical glaucoma patients, which could in turn reflect a different pathogenesis compared to NTG patients without iNPH.
Highlights
Glaucoma is the second leading cause of blindness globally, and is characterized by abnormal increases in intraocular pressure (IOP) that can damage the optic nerve[1,2,3]
The IOP was significantly lower in the idiopathic normal pressure hydrocephalus (iNPH)+/normal-tension glaucoma (NTG)- group compared to the iNPH−/NTG+ group, but there was no significant difference in IOP between the iNPH+/NTG+ and iNPH−/NTG+ groups (Table 1)
We determined the frequency of comorbid NTG and iNPH, investigated possible relationships between the intracranial pressure (ICP) and the presence of glaucoma, and compared the glaucomatous disc morphology of NTG patients between those with and without iNPH
Summary
Glaucoma is the second leading cause of blindness globally, and is characterized by abnormal increases in intraocular pressure (IOP) that can damage the optic nerve[1,2,3]. Reducing the IOP is the only effective therapy to prevent visual impairment and blindness, in hypertensive, and in normotensive individuals; it has been suggested that factors other than the IOP, such as hemodynamic abnormalities, vasospasm, systemic hypotension, and autoimmune diseases may be more important in NTG patients[5,6,7,8] In addition to these vascular risk factors, it has been suggested that differences in CSF pressure may influence the propensity toward glaucomatous damage. It has been reported that a low ICP contributes to worsening NTG11,12; low ICP may lead to an abnormally high TPG in normal IOP, and could result in optic nerve damage at the lamina cribrosa[11,12] This cannot be proven, because it is difficult to measure the actual intraorbital CSF pressure in the subarachnoid space of the optic nerve. The objectives of the present study were to confirm the prevalence of glaucoma in iNPH patients, explore possible associations between ICP and the presence of glaucoma, and investigate disc morphology to determine whether the pathological features of glaucoma patients with iNPH showed any differences, in terms of optic disc morphology and functional test results, compared to those of NTG patients without iNPH
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