Biomaterial Database

The effect of intraocular gas and fluid volumes on intraocular pressure. 1990

J N Simone, and M M Whitacre

Department of Ophthalmology, University of Kansas Medical Center, Kansas City 66103.

Large increases in the intraocular pressure (IOP) of postoperative gas-containing eyes may require the removal of gas or fluid to reduce the IOP to the normal range. Application of the ideal gas law to Friedenwald's equation provides a mathematical model of the relationship between IOP, intraocular gas and fluid volumes, and the coefficient of scleral rigidity. This mathematic model shows that removal of a given volume of gas or fluid produces an identical decrease in IOP and that the more gas an eye contains, the greater the volume reduction necessary to reduce the pressure. Application of the model shows that the effective coefficient of scleral rigidity is low (mean K, 0.0021) in eyes with elevated IOP that have undergone vitrectomy and retinal cryopexy and very low (mean K, 0.0013) in eyes with elevated IOP that have undergone placement of a scleral buckle and band. By using the appropriate mean coefficient of rigidity, the volume of material to be aspirated to produce a given decrease in IOP can be predicted with clinically useful accuracy.

UI	MeSH Term	Description	Entries
D007429	Intraocular Pressure	The pressure of the fluids in the eye.	Ocular Tension,Intraocular Pressures,Ocular Tensions,Pressure, Intraocular,Pressures, Intraocular,Tension, Ocular,Tensions, Ocular
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D001826	Body Fluids	Liquid components of living organisms.	Body Fluid,Fluid, Body,Fluids, Body
D005740	Gases	The vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart. Gases tend to expand indefinitely, to diffuse and mix readily with other gases, to have definite relations of volume, temperature, and pressure, and to condense or liquefy at low temperatures or under sufficient pressure. (Grant & Hackh's Chemical Dictionary, 5th ed)
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D001274	Atmospheric Pressure	The pressure at any point in an atmosphere due solely to the weight of the atmospheric gases above the point concerned.	Atmospheric Pressures,Pressure, Atmospheric,Pressures, Atmospheric
D012590	Sclera	The white, opaque, fibrous, outer tunic of the eyeball, covering it entirely excepting the segment covered anteriorly by the cornea. It is essentially avascular but contains apertures for vessels, lymphatics, and nerves. It receives the tendons of insertion of the extraocular muscles and at the corneoscleral junction contains the CANAL OF SCHLEMM. (From Cline et al., Dictionary of Visual Science, 4th ed)	Scleral Spur,Scleral Spurs,Scleras
D012591	Scleral Buckling	An operation for retinal detachment which reduces the size of the globe by indenting the sclera so that it approximates the retina.	Buckling, Scleral,Bucklings, Scleral,Scleral Bucklings
D014786	Vision Disorders	Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).	Hemeralopia,Macropsia,Micropsia,Day Blindness,Metamorphopsia,Vision Disability,Visual Disorders,Visual Impairment,Blindness, Day,Disabilities, Vision,Disability, Vision,Disorder, Visual,Disorders, Visual,Hemeralopias,Impairment, Visual,Impairments, Visual,Macropsias,Metamorphopsias,Micropsias,Vision Disabilities,Vision Disorder,Visual Disorder,Visual Impairments