Bacterial endophthalmitis: Difference between revisions
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==Pathophysiology== | ==Pathophysiology== | ||
===Exogenous bacterial endophthalmitis=== | |||
'''Postoperative endophthalmitis''' has been reported following nearly every type of ocular surgery, such as cataract, glaucoma, retinal, radial keratotomy, and intravitreal injections. | |||
Following surgical procedure, the eye globe integrity disturbed, as a result microorganisms of the eyelid margin and preocular tear film, most commonly [[coagulase-negative staphylococci]], may invade to the eye. | |||
Preoperative topical antimicrobial agents can decrease colony counts in the tear film, but they do not sterililize the area. The exact low rate of clinical infection following eye surgery (despite the relatively high prevalence of microorganisms in the eye) is not fully understood. It is thought that low rate of clinical infection following surgical procedure is explained by combination of low inoculum levels, low pathogenicity, and the innate ocular defenses against infection. | |||
Postoperative bacterial endophthalmitis may also occur weeks to years following surgery. | |||
''[[Propionibacterium acnes]]'' is the most common microorganism encountered, and clinically evident moderate grade [[inflammation]] may occur weeks to months after surgery. In addition to reflecting the colonization of the preocular tear film, delayed infection is also associated with a higher prevalence of [[streptococcal species]]. | |||
The exact pathogenesis of delayed postoperative bacterial endophthalmitis is not fully understood. It is thought that delayed postoperative bacterial endophthalmitis is caused by either sequesteration of low-virulence organisms introduced at the time of surgery or delayed inoculation of organisms to the eye through either [[wound abnormalities]], [[suture tracks]], or [[filtering blebs]]. | |||
In addition to reflecting the colonization of the preocular tear film, delayed infection is also associated with a higher prevalence of streptococcal species. | |||
===Endogenous bacterial endophthalmitis=== | |||
In endogenous endophthalmitis, blood-borne organisms (seen in patients who are bacteremic in situations such as endocarditis) permeate the blood-ocular barrier either by direct invasion (eg, septic emboli) or by changes in vascular endothelium caused by substrates released during infection. Destruction of intraocular tissues may be due to direct invasion by the organism and/or from inflammatory mediators of the immune response. | |||
Under normal circumstances, the blood-ocular barrier provides a natural resistance against invading organisms. | |||
Destruction of intraocular tissues may be due to direct invasion by the organism and/or from inflammatory mediators of the immune response. | |||
Endophthalmitis may be as subtle as white nodules on the lens capsule, iris, retina, or choroid. It can also be as ubiquitous as inflammation of all the ocular tissues, leading to a globe full of purulent exudate. In addition, inflammation can spread to involve the orbital soft tissue. | |||
==Causes== | ==Causes== |
Revision as of 15:12, 19 July 2016
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Mehrsefat, M.D. [2]
Overview
Bacterial endophthalmitis means bacterial infection inside the eye, involving the vitreous and/or aqueous humors. Most cases of endophthalmitis are exogenous, and organisms are introduced into the eye via trauma, surgery, or an infected cornea. Endogenous endophthalmitis occurs when the eye is seeded via the bloodstream. Patients usually have symptoms from their underlying systemic infection, but sometimes present only with eye symptom
Historical Perspective
Classification
Bacterial endophthalmitis may be classified based on who Infectious agents generally gain access to the posterior segment of the eye into 2 subtypes: exogenous and endogenies.
Based on who Infectious agents generally gain access to the posterior segment of the eye, bacterial endophthalmitis may be classified into:
- Exogenous bacterial endophthalmitis
- Postoperative bacterial endophthalmitis (consequence of intraocular surgery)
- Posttraumatic bacterial endophthalmitis (following a penetrating injury of the globe)
- Endogenous bacterial endophthalmitis (hematogenous spread of bacteria to the eye from a distant anatomical site)
Pathophysiology
Exogenous bacterial endophthalmitis
Postoperative endophthalmitis has been reported following nearly every type of ocular surgery, such as cataract, glaucoma, retinal, radial keratotomy, and intravitreal injections. Following surgical procedure, the eye globe integrity disturbed, as a result microorganisms of the eyelid margin and preocular tear film, most commonly coagulase-negative staphylococci, may invade to the eye. Preoperative topical antimicrobial agents can decrease colony counts in the tear film, but they do not sterililize the area. The exact low rate of clinical infection following eye surgery (despite the relatively high prevalence of microorganisms in the eye) is not fully understood. It is thought that low rate of clinical infection following surgical procedure is explained by combination of low inoculum levels, low pathogenicity, and the innate ocular defenses against infection.
Postoperative bacterial endophthalmitis may also occur weeks to years following surgery. Propionibacterium acnes is the most common microorganism encountered, and clinically evident moderate grade inflammation may occur weeks to months after surgery. In addition to reflecting the colonization of the preocular tear film, delayed infection is also associated with a higher prevalence of streptococcal species. The exact pathogenesis of delayed postoperative bacterial endophthalmitis is not fully understood. It is thought that delayed postoperative bacterial endophthalmitis is caused by either sequesteration of low-virulence organisms introduced at the time of surgery or delayed inoculation of organisms to the eye through either wound abnormalities, suture tracks, or filtering blebs.
In addition to reflecting the colonization of the preocular tear film, delayed infection is also associated with a higher prevalence of streptococcal species.
Endogenous bacterial endophthalmitis
In endogenous endophthalmitis, blood-borne organisms (seen in patients who are bacteremic in situations such as endocarditis) permeate the blood-ocular barrier either by direct invasion (eg, septic emboli) or by changes in vascular endothelium caused by substrates released during infection. Destruction of intraocular tissues may be due to direct invasion by the organism and/or from inflammatory mediators of the immune response. Under normal circumstances, the blood-ocular barrier provides a natural resistance against invading organisms.
Destruction of intraocular tissues may be due to direct invasion by the organism and/or from inflammatory mediators of the immune response.
Endophthalmitis may be as subtle as white nodules on the lens capsule, iris, retina, or choroid. It can also be as ubiquitous as inflammation of all the ocular tissues, leading to a globe full of purulent exudate. In addition, inflammation can spread to involve the orbital soft tissue.