WordNet

the force applied to a unit area of surface; measured in pascals (SI unit) or in dynes (cgs unit); "the compressed gas exerts an increased pressure" (同)pressure level, force per unit area
an oppressive condition of physical or mental or social or economic distress
the somatic sensation that results from applying force to an area of skin; "the sensitivity of his skin to pressure and temperature was normal" (同)pressure_sensation
a force that compels; "the public brought pressure to bear on the government"

PrepTutorEJDIC

〈U〉『押すこと』,『押しつけること』,圧搾,圧縮;〈C〉〈U〉『圧力』,圧力の強さ / 〈U〉『圧迫』,『強制』 / 〈U〉(不快な)圧迫感 / 〈C〉〈U〉(精神的な)重荷,苦脳;(時間・金銭的)切迫 / 〈U〉多忙,あわただしさ / 《おもに米》…‘に'圧力をかける,強制する(《英》pressurise)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/10/10 08:24:16」(JST)

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A patient in front of a tonometer

Intraocular pressure (IOP) is the fluid pressure inside the eye. Tonometry is the method eye care professionals use to determine this. IOP is an important aspect in the evaluation of patients at risk from glaucoma. Most tonometers are calibrated to measure pressure in millimeters of mercury (mmHg).

Physiology

Intraocular pressure is mainly determined by the coupling of the production of aqueous humor and the drainage of aqueous humor mainly through the trabecular meshwork located in the anterior chamber angle.

An important quantitative relationship is provided below:

IOP = F / C + PV

Where F = aqueous fluid formation rate, C = outflow rate, PV = episcleral venous pressure. The above factors are those that drive IOP.

Measurement

Intraocular pressure is measured with a tonometer as part of a comprehensive eye examination.

Measured values of intraocular pressure are influenced by corneal thickness and rigidity.^[1]^[2] As a result, some forms of refractive surgery (such as photorefractive keratectomy) can cause traditional intraocular pressure measurements to appear normal when in fact the pressure may be abnormally high.

Classification

Current consensus among ophthalmologists and optometrists define normal intraocular pressure as that between 10 mmHg and 20 mmHg.^[3]^[4] The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg.^[5]

Ocular hypertension (OHT) is defined by intraocular pressure being higher than normal, in the absence of optic nerve damage or visual field loss.^[6]^[7]

Hypotony, or ocular hypotony, is typically defined as intraocular pressure equal to or less than 5 mmHg.^[8]^[9] Such low intraocular pressure could indicate fluid leakage and deflation of the eyeball.

Influencing factors

Daily variation

Intraocular pressure varies throughout the night and day. The diurnal variation for normal eyes is between 3 and 6 mmHg and the variation may increase in glaucomatous eyes. During the night, intraocular pressure may not decrease^[10] despite the slower production of aqueous humour.^[11] In the general population, IOP ranges between 10 and 21 mm Hg with a mean of about 15 or 16 mm Hg (plus or minus 3.5 mm Hg during a 24-hour cycle).^{[citation needed]}

Fitness and exercise

There is some inconclusive research that indicates that exercise could possibly affect IOP (some positively and some negatively).^[12]^[13] However, some other forms of exercise may raise IOP.^[6]

Musical instruments

Playing some musical wind instruments has been linked to increases in intraocular pressure. One 2011 study focused on brass and woodwind instruments observed "temporary and sometimes dramatic elevations and fluctuations in IOP".^[14] Another study found that the magnitude of increase in intraocular pressure correlates with the intraoral resistance associated with the instrument, and linked intermittent elevation of intraocular pressure from playing high-resistance wind instruments to incidence of visual field loss.^[15] The range of intraoral pressure involved in various classes of ethnic wind instruments, such as Native American flutes, has been shown to be generally lower than Western classical wind instruments.^[16]

Other factors

Intraocular pressure also varies with a number of other factors such as heart rate, respiration, fluid intake, systemic medication and topical drugs. Alcohol consumption leads to a transient decrease in intraocular pressure and caffeine may increase intraocular pressure.^[17]

Taken orally, glycerol (often mixed with fruit juice to reduce its sweet taste) can cause a rapid, temporary decrease in intraocular pressure. This can be a useful initial emergency treatment of severely elevated pressure.^[18]

Significance

Ocular hypertension is the most important risk factor for glaucoma.

Intraocular pressure has been measured as a secondary outcome in a systematic review comparing the effect of neuroprotective agents in slowing the progression of open angle glaucoma.^[19]

Differences in pressure between the two eyes is often clinically significant, and potentially associated with certain types of glaucoma, as well as iritis or retinal detachment.

Intraocular pressure may become elevated due to anatomical problems, inflammation of the eye, genetic factors, or as a side-effect from medication. Intraocular pressure usually increases with age and is genetically influenced.^[20]

References

^ Grieshaber MC, Schoetzau A, Zawinka C, Flammer J, Orgul S (June 2007). "Effect of Central Corneal Thickness on Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Primary Open-angle Glaucoma". Arch Ophthalmol. 125 (6): 740–44. doi:10.1001/archopht.125.6.740. PMID 17562982.
^ Tanaka GH (April 1998). "Corneal pachymetry: a prerequisite for applanation tonometry?". Arch Ophthalmol. 116 (4): 544–5. PMID 9565063.
^ webMD - Tonometry
^ Glaucoma Overview from eMedicine
^ Janunts E. "Optical remote sensing of intraocular pressure by an implantable nanostructured array". Medizinische Fakultät der Universität des Saarlandes.
^ ^a ^b Viera GM, Oliveira HB, de Andrade DT, Bottaro M, Ritch R (September 2006). "Intraocular Pressure Variation During Weight Lifting". Arch Ophthalmol. 124 (9): 1251–54. doi:10.1001/archopht.124.9.1251. PMID 16966619.
^ American Optometric Association - Ocular Hypertension
^ eMedicine - Ocular Hypotony - Author: Sheila P Sanders, MD
^ Henderer JD, Budenz DL, Flynn HW Jr, Schiffman JC, Feuer WJ, Murray TG (February 1999). "Elevated Intraocular Pressure and Hypotony Following Silicone Oil Retinal Tamponade for Complex Retinal Detachment: Incidence and Risk Factors". Arch Ophthalmol. 117 (2): 189–95. doi:10.1001/archopht.117.2.189. PMID 10037563.
^ Liu JHK; Weinreb RN (2011). "Monitoring intraocular pressure for 24 h". Br J Ophthalmol 95 (5): 599–600. doi:10.1136/bjo.2010.199737.
^ Brubaker RF (1991). "Flow of aqueous humor in humans". Invest Ophthalmol Vis Sci 32 (13): 3145–3166.
^ Studies have also been conducted on both healthy and sedentary individuals to determine if intraocular pressure could be reduced with other types of exercise. Some forms of exertion have been found to result in a decrease in intraocular pressure. Exercises studied included; walking, jogging, and running. Acute Dynamic Exercise Reduces Intraocular Pressure, Departments of Ophthalmology, Physiology, Faculty of Medicine, Atatürk University, Erzurum- Turkey. July 1999.
^ Qureshi IA. Effects of mild, moderate and severe exercise on intraocular pressure of sedentary subjects. Rawalpindi Medical College, Rawalpindi, Pakistan
^ Gunnar Schmidtmann; Susanne Jahnke; Egbert J. Seidel; Wolfgang Sickenberger; Hans-Jürgen Grein (2011). "Intraocular Pressure Fluctuations in Professional Brass and Woodwind Musicians During Common Playing Conditions". Graefe's Archive for Clinical and Experimental Ophthalmology 249 (6): 895–901. doi:10.1007/s00417-010-1600-x.
^ J. S. Schuman; E. C. Massicotte; S. Connolly; E. Hertzmark; B. Mukherji; M. Z. Kunen (January 2000). "Increased Intraocular Pressure and Visual Field Defects in High Resistance Wind Instrument Players". Ophthalmology 107 (1): 127–133. doi:10.1016/s0161-6420(99)00015-9.
^ Clinton F. Goss (August 2013). Intraoral Pressure in Ethnic Wind Instruments (PDF). arXiv:1308.5214. Retrieved 22 Aug 2013. Lay summary.
^ Intraocular pressure measure on normal eyes by Pardianto G et al., in Mimbar Ilmiah Oftalmologi Indonesia.2005;2:78-9.
^ Effect of Oral Glycerol on Intraocular Pressure in Normal and Glaucomatous Eyes, S. M. Drance, MD, FRCS (ENG) Arch Ophthalmol. 1964;72(4):491-493. doi:10.1001/archopht.1964.00970020491009
^ Sena DF, Lindsley K (2013). "Neuroprotection for treatment of glaucoma in adults". Cochrane Database Syst Rev 2: CD006539. doi:10.1002/14651858.CD006539.pub3. PMC 3478138. PMID 20166085.
^ Intraocular pressure measure on normal eyes by Pardianto G et al., in Mimbar Ilmiah Oftalmologi Indonesia.2005;2: 80.

External links

www.allaboutvision.com What To Expect During a Comprehensive Eye Exam
www.emedicinehealth.com Ocular Hypertension
www.opt.indiana.edu Non-Contact Tonometry

UpToDate Contents

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English Journal

Influence of glucocorticosteroids on the biomechanical properties of in-vivo rabbit cornea.

Yu JG, Bao FJ, Joda A, Fu XA, Zhou S, Wang J, Hu XL, Wang QM, Elsheikh A.SourceSchool of Optometry and Ophthalmology and Eye Hospital, Wenzhou Medical College, Wenzhou, Zhejiang Province 325027, China; The Central Hospital of Wuhan, No. 26, Shengli street, Jiang'an District, Wuhan, Hubei Province 430000, China.
Journal of the mechanical behavior of biomedical materials.J Mech Behav Biomed Mater.2014 Jan;29:350-9. doi: 10.1016/j.jmbbm.2013.08.015. Epub 2013 Aug 28.
Understanding corneal biomechanical responses during long-term glucocorticosteroids administration is important in clinical practice. The purpose of this study is to investigate the biomechanical influence of fluorometholone 0.1% eye drops on rabbit cornea. Thirty-eight Japanese white rabbits were r
PMID 24161489

Glaucoma and the applications of carbonic anhydrase inhibitors.

Scozzafava A, Supuran CT.SourceLaboratorio di Chimcia Bioinorganica, Universita degli Studi di Firenze, Florence, Italy, andrea.scozzafava@unifi.it.
Sub-cellular biochemistry.Subcell Biochem.2014;75:349-59. doi: 10.1007/978-94-007-7359-2_17.
Inhibition of carbonic anhydrase (CA, EC 4.2.1.1) has pharmacologic applications in the treatment of glaucoma, a disease affecting a large number of people and characterized by an elevated intraocular pressure (IOP). At least three isoforms, CA II, IV and XII are targeted by the sulfonamide inhibito
PMID 24146387

Measurement of the difference in intraocular pressure between the sitting and lying body positions in healthy subjects: direct comparison of the Icare Pro with the Goldmann applanation tonometer, pneumatonometer and Tonopen XL.

Barkana Y, Gutfreund S.SourceDepartment of Ophthalmology, Assaf Harofe Medical Center, Zerifin, Israel.
Clinical & experimental ophthalmology.Clin Experiment Ophthalmol.2013 Dec 3. doi: 10.1111/ceo.12272. [Epub ahead of print]
BACKGROUND: Change in intraocular pressure (IOP) is known to occur with body posture. Previous studies have reported markedly different estimations of this change. The Icare Pro is a new device that is designed to measure IOP with the subject supine. We compared the measurement of postural change in
PMID 24299102

Japanese Journal

臨床研究広義の原発開放隅角緑内障患者に対する自動静的視野検査直後の冬期における一過性眼圧上昇

西野和明,吉田富士子,新田朱里 [他]
日本眼科学会雑誌 117(12), 990-995, 2013-12
NAID 40019912288

Acute Changes in Central Corneal Thickness According to Experimental Adjustment of Intraocular Pressure in Normal Canine Eyes

PARK Young-Woo,JEONG Man-Bok,LEE Eui Ri [他]
The journal of veterinary medical science 75(11), 1479-1483, 2013-11
NAID 40019886525

すでに行われていた緑内障治療が不要と判断された症例の検討

茨木信博,久保江理,佐々木洋 [他]
あたらしい眼科 30(10), 1472-1474, 2013-10
NAID 40019838136

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リンク元	「眼圧」「IOP」「ocular tension」「intraocular tension」
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