title: Pressure balance and imbalance in the optic nerve chamber: The Beijing Intracranial and Intraocular Pressure (iCOP) Study.
abstract: To determine the interdependence of intracranial pressure (ICP) and intraocular pressure (IOP) and how it affects optic nerve pressures, eight normal dogs were examined using pressure-sensing probes implanted into the left ventricle, lumbar cistern, optic nerve subarachnoid space in the left eye, and anterior chamber in the left eye. This allowed ICP, lumbar cistern pressure (LCP), optic nerve subarachnoid space pressure (ONSP) and IOP to be simultaneously recorded. After establishing baseline pressure levels, pressure changes that resulted from lowering ICP (via shunting cerebrospinal fluid (CSF) from the ventricle) were recorded. At baseline, all examined pressures were different (ICP<LCP<ONSP), but correlated (P>0.001). As ICP was lowered during CSF shunting, IOP also dropped in a parallel time course so that the trans-lamina cribrosa gradient (TLPG) remained stable (ICP-IOP dependent zone). However, once ICP fell below a critical breakpoint, ICP and IOP became uncoupled and TLPG changed as ICP declined (ICP-IOP independent zone). The optic nerve pressure gradient (ONPG) and trans-optic nerve pressure gradient (TOPG) increased linearly as ICP decreased through both the ICP-IOP dependent and independent zones. We conclude that ICP and IOP are coupled in a specific pressure range, but when ICP drops below a critical point, IOP and ICP become uncoupled and TLPG increases. When ICP drops, a rise in the ONPG and TOPG creates more pressure and reduces CSF flow around the optic nerve. This change may play a role in the development and progression of various ophthalmic and neurological diseases, including glaucoma.
authors.affiliation: Department of Neurosurgery, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
authors.forename: Ruowu
authors.initials: R
authors.lastname: Hou
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.|Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
authors.forename: Diya
authors.initials: D
authors.lastname: Yang
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.|Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
authors.forename: Huaizhou
authors.initials: H
authors.lastname: Wang
authors.affiliation: Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China.
authors.forename: Weiwei
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Ophthalmology, Xuanwu Hospital, Capital Medical University, Beijing, 100053, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
authors.forename: Jinghong
authors.initials: J
authors.lastname: Sang
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
authors.forename: Sumeng
authors.initials: S
authors.lastname: Liu
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China.
authors.forename: Yiwen
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Ophthalmology, Eye Hospital of China Academy of Chinese Medical Sciences, Beijing, 100040, China.
authors.forename: Xiaobin
authors.initials: X
authors.lastname: Xie
authors.affiliation: Eye center, New York Eye and Ear Infirmary, New York, 10003, USA.
authors.forename: Ruojing
authors.initials: R
authors.lastname: Ren
authors.affiliation: Department of Endoscopic and Microinvasive Neurosurgery, Beijing Neurosurgery Institute, Beijing Tiantian Hospital, Capital Medical University, Beijing, 100050, China. zyz2004520@yeah.net.
authors.forename: Yazhuo
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Institute of Medical Psychology, Medical Faculty, Otto-v.-Guericke University of Magdeburg, Magdeburg, 39120, Germany.
authors.forename: Bernhard A
authors.initials: BA
authors.lastname: Sabel
authors.affiliation: Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing, 100730, China. wningli@vip.163.com.|Beijing Institute of Ophthalmology, Beijing Tongren Hospital, Capital Medical University, Beijing, 100730, China. wningli@vip.163.com.
authors.forename: Ningli
authors.initials: N
authors.lastname: Wang
mesh_terms: D006801:Humans; D007427:Intracranial Pressure; D007429:Intraocular Pressure; D009900:Optic Nerve / Q000502:physiology*
keywords: glaucoma; optic nerve pressure gradient (ONPG); optic neuropathy; trans-lamina cribrosa pressure gradient (TLPG); trans-optic canal pressure gradient (TCPG); trans-optic nerve pressure gradient (TOPG)