WordNet

the act of releasing from an attachment or connection (同)disengagement
a small unit of troops of special composition
relating to or resembling or derived from or containing glass; "vitreous rocks"; "vitreous silica"
of or relating to or constituting the vitreous humor of the eye; "the vitreous chamber"

PrepTutorEJDIC

〈U〉(…から…を)分離すること,取り外すこと《+『of』+『名』+『from』+『名』》 / 〈U〉超然としていること / 〈U〉私心(偏見)のないこと / 〈C〉(特別の任務を帯びた)分遣隊,特派部隊
ガラスの;ガラス製の;ガラス状の

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/08/18 16:05:50」(JST)

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A posterior vitreous detachment (PVD) is a condition of the eye in which the vitreous membrane separates from the retina. It refers to the separation of the posterior hyaloid membrane from the retina anywhere posterior to the vitreous base (a 3-4mm wide attachment to the ora serrata.) Synchysis: there is associated vitreous liquefaction. Syneresis: there is collapse of the vitreous due to collection of synchytic fluid between the posterior hyaloid membrane and the internal limiting membrane of the retina.

Broadly speaking, the condition is common for older adults and over 75% of those over the age of 65 develop it. Although less common among people in their 40s or 50s, the condition is not rare for those individuals. Some research has found that the condition is more common among women.^[1]^[2]

Causes and risk factors[edit source | edit]

The vitreous (Latin="glassy") is a gel which fills the eye behind the lens. Between it and the retina is the vitreous membrane. Over time the vitreous changes, shrinking and developing pockets of liquefaction, similar to the way a gelatin dessert shrinks, or detaches, from the edge of a pan over time. At some stage the vitreous membrane may peel away from the retina. This is usually a sudden event, but may also occur slowly over months.

Age and refractive error play a role in determining the onset of PVD in a healthy person. PVD is rare in emmetropic people under the age of 40 years, and increases with age to 86% in the 90s. Several studies have found a broad range of incidence of PVD, from 20% of autopsy cases to 57% in a more elderly population of patients (average age was 83.4 years).

People with myopia (nearsightedness) greater than 6 diopters are at higher risk of PVD at all ages. Posterior vitreous detachment does not directly threaten vision. Even so, it is of increasing interest because the interaction between the vitreous body and the retina might play a decisive role in the development of major pathologic vitreoretinal conditions, such as epiretinal membrane.

PVD may also occur in cases of cataract surgery, within weeks or months of the surgery.

The vitreous membrane is more firmly attached to the retina anteriorly, at a structure called the vitreous base. The membrane does not normally detach from the vitreous base, although it can be detached with extreme trauma. However, the vitreous base may have an irregular posterior edge. When the edge is irregular, the forces of the vitreous membrane peeling off the retina can become concentrated at small posterior extensions of the vitreous base. Similarly, in some people with retinal lesions such as lattice retinal degeneration or chorio-retinal scars, the vitreous membrane may be abnormally adherent to the retina. If enough traction occurs the retina may tear at these points. If there are only small point tears, these can allow glial cells to enter the vitreous and proliferate to create a thin epiretinal membrane that distorts vision. In more severe cases, vitreous fluid may seep under the tear, separating the retina from the back of the eye, creating a retinal detachment. Trauma can be any form from a blunt force trauma to the face such as a boxer's punch or even in some cases has been known to be from extremely vigorous blowing of the nose.

Symptoms[edit source | edit]

When this occurs there is a characteristic pattern of symptoms:

Flashes of light (photopsia)
A sudden dramatic increase in the number of floaters
A ring of floaters or hairs just to the temporal side of the central vision

As a posterior vitreous detachment proceeds, adherent vitreous membrane may pull on the retina. While there are no pain fibers in the retina, vitreous traction may stimulate the retina, with resultant flashes that can look like a perfect circle.^{[citation needed]}

If a retinal vessel is torn, the leakage of blood into the vitreous cavity is often perceived as a "shower" of floaters. Retinal vessels may tear in association with a retinal tear, or occasionally without the retina being torn.

Complications[edit source | edit]

The risk of retinal detachment is greatest in the first 6 weeks following a vitreous detachment, but can occur over 3 months after the event.

The risk of retinal tears and detachment associated with vitreous detachment is higher in patients with myopic retinal degeneration, lattice degeneration, and a familial or personal history of previous retinal tears/detachment.

Treatment[edit source | edit]

Therapy is not required or indicated in posterior vitreous detachment, unless there are associated retinal tears, which need to be repaired.^[3] In absence of retinal tears, the usual progress is that the vitreous will continue to age and liquefy and floaters will usually become less and less noticeable, and eventually most symptoms will completely disappear.^[3] Prompt examination of patients experiencing vitreous floaters combined with expeditious treatment of any retinal tears has been suggested as the most effective means of preventing certain types of retinal detachments.^[4]

References[edit source | edit]

^ http://www.ncbi.nlm.nih.gov/pubmed/10163464
^ http://www.rnib.org.uk/eyehealth/eyeconditions/eyeconditionsoz/Pages/posterior_vitreous_detachment.aspx
^ ^a ^b Posterior Vitreous Detachment from Cleveland Clinic. This document was last reviewed on: 12/24/2008
^ Byer NE. "Natural history of posterior vitreous detachment with early management as the premier line of defense against retinal detachment." Ophthalmology. 1994 Sep;101(9):1503-13; discussion 1513-4. PMID 8090453.

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English Journal

Unusual Adverse Choroidal Reaction to Intravitreal Bevacizumab in Aggressive Posterior Retinopathy of Prematurity: The Indian Twin Cities ROP Screening (ITCROPS) Data Base Report Number 7.

Chhablani J, Rani PK, Balakrishnan D, Jalali S.SourceSrimati Kannuri Santhamma Centre for Vitreo Retinal Diseases, L. V. Prasad Eye Institute, Hyderabad Eye Research Foundation , Hyderabad , India.
Seminars in ophthalmology.Semin Ophthalmol.2013 Oct 11. [Epub ahead of print]
Abstract Purpose: To describe a case of choroidal ischemia in a neonate after single, bilateral, intravitreal bevacizumab (IVB) injection for severe zone 1 aggressive posterior retinopathy of prematurity (AP-ROP). Methods: A six-week-old baby, born at a gestation age of 28 weeks and birth weight of
PMID 24117452

Serpiginous Choroiditis with Atypical Presentation Treated with Intravenous Methyl Prednisolone.

Balakrishnan D, Mathai A, Gogte P, Tibra N, Chhablani J.SourceSmt. Kannuri Santhamma Centre for Retina Vitreous Diseases, L. V. Prasad Eye Institute, L. V. Prasad Marg , Hyderabad , India.
Seminars in ophthalmology.Semin Ophthalmol.2013 Oct 11. [Epub ahead of print]
Abstract Purpose: The purpose of this study is to report a case of atypical serpiginous choroiditis presenting with disc edema and exudative retinal detachment, treated successfully with intravenous methyl prednisolone. Methods: A 45-year-old male patient presented with sudden decrease of vision in
PMID 24117451

Early structural changes during spontaneous closure of idiopathic full-thickness macular hole determined by optical coherence tomography: a case report.

Okubo A, Unoki K, Yamakiri K, Sameshima M, Sakamoto T.AbstractBACKGROUND: Spontaneous closure of an idiopathic full-thickness macular hole has been reported to occasionally occur. However, the cells involved in plugging the macular hole have not been determined conclusively. We aimed to report the early structural changes that occur during a spontaneous closure of an idiopathic full-thickness macular hole determined by spectral-domain optical coherence tomography.
BMC research notes.BMC Res Notes.2013 Oct 2;6(1):396. [Epub ahead of print]
BACKGROUND: Spontaneous closure of an idiopathic full-thickness macular hole has been reported to occasionally occur. However, the cells involved in plugging the macular hole have not been determined conclusively. We aimed to report the early structural changes that occur during a spontaneous closur
PMID 24083650

Japanese Journal

Timing of Prophylactic and Early Vitrectomy for First-Presenting or Recurrent Acute Retinal Necrosis Syndrome

Matsuo Toshihiko
Acta Medica Okayama 66(6), 493-497, 2012-12-00
… Case 1, a 72-year-old man, had a second recurrence of ARNS in the left eye in 2011 and underwent early vitrectomy in the acute inflammatory phase to remove previously formed vitreous opacity and vitreoretinal adhesions, in parallel with intravenous acyclovir and oral prednisolone administration. … She underwent a vitrectomy in the post-inflammatory phase, since epiretinal proliferation was noted through vitreous opacity with complete posterior vitreous detachment. …
NAID 120005082624

巨大裂孔網膜剥離の手術検討

長谷川英稔,武藤哲也,松本行弘,筑田眞
Dokkyo journal of medical sciences 39(2), 113-117, 2012-07-25
巨大裂孔網膜剥離9 例9 眼を過去4 年間に経験し,手術手技と成績について検討したので報告する.裂孔の大きさは180 度が2 眼,120 度が4 眼,100 度が1 眼,90 度が2 眼であった.全症例に初回手術として経毛様体扁平部硝子体手術(PPV)を行った.輪状締結術(EN)併用が7 眼で,液体パーフルオロカーボン(PFCL)を用いたものは6 眼,タンポナーデ物質はシリコーンオイル(SO)が5 …
NAID 110009443667