Intraocular pressure: Difference between revisions

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==Classification==
==Classification==
Current consensus among ophthalmologists and optometrists define normal intraocular pressure as that between 10 [[mmHg]] and 20 mmHg.<ref>[http://www.webmd.com/hw/lab_tests/hw201323.asp webMD - Tonometry]</ref><ref>[http://www.emedicinehealth.com/articles/14545-1.asp Glaucoma Overview] from eMedicine</ref> The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg.<ref name=Janunts>{{Cite web|url=http://www.uniklinikum-saarland.de/de/einrichtungen/kliniken_institute/experimentelle_ophthalmologie/forschung/iop_sensing/| title=Optical remote sensing of intraocular pressure by an implantable nanostructured array
Current consensus among ophthalmologists and optometrists define normal intraocular pressure as that between 10 [[mmHg]] and 20 mmHg.<ref>[http://www.webmd.com/hw/lab_tests/hw201323.asp webMD - Tonometry]</ref><ref>[http://www.emedicinehealth.com/articles/14545-1.asp Glaucoma Overview] from eMedicine</ref> The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg.<ref name=Janunts>{{Cite web|url=http://www.uniklinikum-saarland.de/de/einrichtungen/kliniken_institute/experimentelle_ophthalmologie/forschung/iop_sensing/|title=Optical remote sensing of intraocular pressure by an implantable nanostructured array|author=Janunts E|work=Medizinische Fakultät der Universität des Saarlandes|deadurl=yes|archiveurl=https://web.archive.org/web/20120425132825/http://www.uniklinikum-saarland.de/de/einrichtungen/kliniken_institute/experimentelle_ophthalmologie/forschung/iop_sensing/|archivedate=2012-04-25|df=}}</ref>
|author=Janunts E|work=Medizinische Fakultät der Universität des Saarlandes}}</ref>


[[Ocular hypertension]] (OHT) is defined by intraocular pressure being higher than normal, in the absence of [[optic nerve]] damage or [[visual field]] loss.<ref name="Vieira">{{cite journal |vauthors=Viera GM, Oliveira HB, de Andrade DT, Bottaro M, Ritch R |title=Intraocular Pressure Variation During Weight Lifting |journal=Arch Ophthalmol. |volume=124 |issue=9 |pages=1251–54 |date=September 2006 |url=http://archopht.ama-assn.org/cgi/content/full/124/9/1251 |pmid=16966619 |doi=10.1001/archopht.124.9.1251}}</ref><ref>[http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/ocular-hypertension?sso=y Ocular Hypertension], [[American Optometric Association]]. Accessed 2015-11-3.</ref>
[[Ocular hypertension]] (OHT) is defined by intraocular pressure being higher than normal, in the absence of [[optic nerve]] damage or [[visual field]] loss.<ref name="Vieira">{{cite journal |vauthors=Viera GM, Oliveira HB, de Andrade DT, Bottaro M, Ritch R |title=Intraocular Pressure Variation During Weight Lifting |journal=Arch Ophthalmol. |volume=124 |issue=9 |pages=1251–54 |date=September 2006 |url=http://archopht.ama-assn.org/cgi/content/full/124/9/1251 |pmid=16966619 |doi=10.1001/archopht.124.9.1251}}</ref><ref>[http://www.aoa.org/patients-and-public/eye-and-vision-problems/glossary-of-eye-and-vision-conditions/ocular-hypertension?sso=y Ocular Hypertension], [[American Optometric Association]]. Accessed 2015-11-3.</ref>

Revision as of 20:37, 15 November 2017

tonometer

Intraocular pressure (IOP) is the fluid

mmHg
).

Physiology

Intraocular pressure is mainly determined by the coupling of the production of

anterior chamber angle. The reason for this is because the vitreous humour in the posterior segment
has a relatively fixed volume and thus does not affect intraocular pressure regulation.

An important quantitative relationship is provided below [2]:

Po=(F−U)/C+Pv

Where:

  • Po is the IOP in millimeters of mercury (mmHg)
  • F the rate of aqueous humour formation in microliters per minute (μL/min)
  • U the resorption of aqueous humour through the uveoscleral route (in μL/min)
  • C is the facility of outflow in microliters per minute per millimeter of mercury (μL/min/mmHg)
  • Pv the episcleral venous pressure in millimeters of mercury (mmHg).

The above factors are those that drive IOP.

Diaton transpalpebral tonometer

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.[3][4] 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. A newer transpalpebral and transsleral tonometry method is not influenced by corneal biomechanics and does not need to be adjusted or corneal irregularities as measurement is done over upper eyelid and sclera.[5]

Classification

Current consensus among ophthalmologists and optometrists define normal intraocular pressure as that between 10

mmHg and 20 mmHg.[6][7] The average value of intraocular pressure is 15.5 mmHg with fluctuations of about 2.75 mmHg.[8]

Ocular hypertension (OHT) is defined by intraocular pressure being higher than normal, in the absence of optic nerve damage or visual field loss.[9][10]

Ocular hypotension, Hypotony, or ocular hypotony, is typically defined as intraocular pressure equal to or less than 5 mmHg.[11][12] 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[13] despite the slower production of aqueous humour.[14] 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).[15][16]

Fitness and exercise

There is some inconclusive research that indicates that exercise could possibly affect IOP (some positively and some negatively).[17][18] However, some other forms of exercise may raise IOP.[9]

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".[19] 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.[20] 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.[21]

Drugs

Intraocular pressure also varies with a number of other factors such as heart rate, respiration, fluid intake, systemic medication and topical drugs. Alcohol and marijuana consumption leads to a transient decrease in intraocular pressure and caffeine may increase intraocular pressure.[22]

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.[23]

The depolarising muscle relaxant

choroidal blood vessels. Ketamine also increases IOP.[24]

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.[25]

Differences in pressure between the two eyes are 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,

nerve fiber layer. Sudden intraocular pressure drop can lead to intraocular decompression that generates micro bubbles that potentially cause multiple micro emboli and leading to hypoxia, ischemia and retinal micro structure damage.[26]

References

  1. PMID 25400274
    .
  2. doi:10.1016/j.preteyeres.2016.07.002
    .
  3. PMID 17562982
    .
  4. PMID 9565063
    .
  5. PMID 26167293
    .
  6. ^ webMD - Tonometry
  7. ^ Glaucoma Overview from eMedicine
  8. ^ Janunts E. "Optical remote sensing of intraocular pressure by an implantable nanostructured array". Medizinische Fakultät der Universität des Saarlandes. Archived from the original on 2012-04-25. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  9. ^
    PMID 16966619
    .
  10. ^ Ocular Hypertension, American Optometric Association. Accessed 2015-11-3.
  11. ^ "Ocular Hypotony: Background, Pathophysiology, Epidemiology". Medscape Reference. 2014-02-05. Retrieved 2015-11-04.
  12. PMID 10037563
    .
  13. PMID 21330554
    .
  14. PMID 1748546
    .
  15. PMID 15923494
    .
  16. ^ Pooranee (2015-10-09). "Do you know about Intra Ocular Pressure?". Health Education Bureau, Information and Communication Technology Agency, Sri Lanka. Retrieved 2015-11-04.
  17. ^ 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.
  18. ^ Qureshi IA. Effects of mild, moderate and severe exercise on intraocular pressure of sedentary subjects. Rawalpindi Medical College, Rawalpindi, Pakistan
  19. ^ 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
    .
  20. ^ 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.
    PMID 10647731
    .
  21. ^ Clinton F. Goss (August 2013). "Intraoral Pressure in Ethnic Wind Instruments" (PDF). Flutopedia.
    Bibcode:2013arXiv1308.5214G
    . Retrieved 22 Aug 2013.
  22. ^ Intraocular pressure measure on normal eyes by Pardianto G et al., in Mimbar Ilmiah Oftalmologi Indonesia.2005;2:78-9.
  23. doi:10.1001/archopht.1964.00970020491009
  24. ISBN 978-0-07-162442-8.{{cite book}}: CS1 maint: multiple names: authors list (link
    )
  25. PMID 28122126
    .
  26. PMID 25804599
    .

External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Intraocular_pressure&oldid=810529006"