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Introduction to Physiological Regulators and Control Systems
Published in Robert B. Northrop, Endogenous and Exogenous Regulation and Control of Physiological Systems, 2020
Clearly, in the steady state, the AH must exit the eye at the same volume flow rate at which it enters. Outflow of AH is through the canal of Schlemm, into the episcleral veins, then into the main venous circulation, etc. The eyeball is slightly elastic, with most of its compliance coming from the thin, clear cornea. Normal intraocular pressure (IOP) is about 16 mmHg. If there is an increase in the outflow resistance, the normal IOP rises, and if the IOP exceeds its normal high range (about 30 mmHg), the condition known as glaucoma exists. In extreme situations, the IOP can exceed 60 to 80 mmHg. Such acute glaucoma sharply reduces normal arterial blood flow to the retina, causing poor oxygenation and impaired nutrition of retinal neurons and glial cells. If prolonged, glaucoma can lead to the death of retinal neurons, including the loss of retinal ganglion cells which comprise the optic nerve. Such neuron loss is irreversible, and it causes loss of visual acuity and even total blindness.
Symmetry Studies
Published in Marlos A. G. Viana, Vasudevan Lakshminarayanan, Symmetry in Optics and Vision Studies, 2019
Marlos A. G. Viana, Vasudevan Lakshminarayanan
The intraocular pressure (IOP) is the fluid pressure inside the eye created by the fluids, aqueous and vitreous humor, within the eye. Quantification of IOP is one of the most important parameters in the diagnosis of patients, for example, patients at risk from glaucoma, a major blinding disease. The method of quantifying the IOP is called tonometry and is calibrated to quantify it in millimeters of mercury (mmHg). IOP values are influenced by corneal thickness and rigidity. Corneal thickness is quantified by a technique called pachymetry. Normal values of IOP vary between 10 and 20 mmHg. The quantification of the corneal thickness and IOP in the same eye is an example of a joint bilateral quantification allowing for the increased efficiency of treatment of the condition and monitoring its progression or remission.
Human physiology, hazards and health risks
Published in Stephen Battersby, Clay's Handbook of Environmental Health, 2023
Revati Phalkey, Naima Bradley, Alec Dobney, Virginia Murray, John O’Hagan, Mutahir Ahmad, Darren Addison, Tracy Gooding, Timothy W Gant, Emma L Marczylo, Caryn L Cox
Vision The iris is smooth muscle and the sympathetic nervous system enlarges the pupil while the parasympathetic nervous system constricts the pupil.The ciliary muscle controls the shape of the lens and is controlled by parasympathetic nerves.The cornea focuses the image on the retina and light rays are bent passing from air into the cornea.The lens is elastic and makes adjustments for distance by changing shape (accommodation). Opacity of the lens is called a cataract.The retina is a thin layer of neural tissue with light receptors termed rods and cones. Light rays hit the rods, cones, and transmit signals via bipolar cells – contained in the retina to the topic cortex of the brain.The aqueous humour maintains the intraocular pressure and there may be a role in immune response to defend against pathogens. Its main function is to provide dioptric power to the cornea. Glaucoma is a condition characterised by increased intraocular pressure (pressure within the eye) either through increased production or decreased outflow of aqueous humour.The optic nerve is connected to the thalamus and then the visual cortex within the brain (see later). (See Figure 10.2.)
Influence of the breathing pattern during resistance training on intraocular pressure
Published in European Journal of Sport Science, 2020
Jesús Vera, Alejandro Perez-Castilla, Beatríz Redondo, Juan Carlos De La Cruz, Raimundo Jiménez, Amador García-Ramos
Glaucoma is characterized by a progressive optic neuropathy that causes the death of retinal ganglion cells and, subsequently, visual loss (Weinreb, Aung, & Medeiros, 2014). Nowadays, glaucoma affects more than 70 million people worldwide and it is estimated to increase to approximately 110 million by 2040 (Tham et al., 2014). Reduction of intraocular pressure (IOP) is the only proven method to treat glaucoma, and pressure-lowering medications are the mainstay treatment for this disease (Heijl et al., 2002). However, IOP values should be reduced using as little medication as possible to minimize side effects (Yee, 2007). In this regard, daily life activities such as food intake (Giaconi et al., 2012; Kang et al., 2016), sleeping position (Prata, De Moraes, Kanadani, Ritch, & Paranhos, 2010), caffeine intake (Li, Wang, Guo, Wang, & Sun, 2011; Vera, Redondo, Molina, Bermúdez, & Jiménez, 2019), smoking (Chan et al., 2016) or the practice of physical exercise (Zhu et al., 2018) have also demonstrated to affect IOP values.
Multi-modal classifier fusion with feature cooperation for glaucoma diagnosis
Published in Journal of Experimental & Theoretical Artificial Intelligence, 2019
Nacer Eddine Benzebouchi, Nabiha Azizi, Amira S. Ashour, Nilanjan Dey, R. Simon Sherratt
Glaucoma is considered the second reason for visual deterioration after age-related macular degeneration (AMD). Over 70 million people would be affected worldwide by 2020 (Quigley & Broman, 2006). Glaucoma can be managed, but can also cause blindness if not detected in time. Glaucoma is an eye disease that primarily affects people over 45 years of age. This illness can cause optic nerve lesion; the nerve begins with the retina in the back of the eye and carries the images to the brain. When this nerve is damaged, the visual field is reduced, the vision is then modified and this can lead to long-term blindness. In most cases, glaucoma is linked to an increase in the pressure inside the eye, also termed intraocular hypertension or intraocular pressure (IOP).
XEN Gel Implant: a new surgical approach in glaucoma
Published in Expert Review of Medical Devices, 2018
Ankita Chaudhary, Lauriane Salinas, Jacopo Guidotti, André Mermoud, Kaweh Mansouri
Glaucoma is the second leading cause of blindness, affecting more than 70 million people worldwide with approximately 10% being bilaterally blind, making it the leading cause of irreversible blindness in the world [1]. Glaucoma is defined as a chronic progressive optic neuropathy, characterized by typical optic disk and retinal nerve fiber layer changes with corresponding visual field defects. An elevated intraocular pressure (IOP) has been considered as a major risk factor. The biological basis of glaucoma is poorly understood and the factors contributing to its progression have not been fully identified [2].