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Neural Biology 1 > introduction to pathology of the eye > Flashcards

introduction to pathology of the eye Flashcards

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1
Q

what is inflammation?

A
  • the body’s response to potentially damaging stimuli
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2
Q

what are the causes of inflammation in the eye ?

A
  • infection with pathogen
  • hypersensitivity reactions ( inappropriate inflammatory response )
  • autoimmunity
  • trauma ( including iatrogenic)
  • chemical/toxic
  • radiation
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3
Q

what are the two types of inflammation ?

A

1- acute inflammation
. short duration ( minutes or days )
. usually resolves but sometimes progresses to chronic inflammation
2- chronic inflammation
. weeks or months
. may be secondary to acute
. can also develop without acute inflammation

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4
Q

what are the signs of acute inflammation?

A
  • rubor - redness
  • calor - warmth
  • dolor - pain
  • tumor - swelling
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5
Q

what are the major features of acute inflammation ?

A

1- vascular events

2- cellular events

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6
Q

what are vascular and cellular events triggered by ?

A
  • triggered by chemical mediators also referred to inflammatory mediators such as ( histamine )which also perpetuate the inflammatory process
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7
Q

describe the vascular events of acute inflammation ?

A

. vasodilation
- blood vessels get bigger

. increased blood flow to a tissue which generates warmth as more blood is coming into the area
. blood vessels change their characteristics and become more leaky and gives rise to more swelling

. increased vascular permeability

. movement of inflammatory cells from blood vessels to site of injury

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8
Q

describe the cellular events of acute inflammation ?

A
  • cellular events are cells that have a particular role in the inflammatory response and several of those cells are circulating in the blood
  • a classic example would be neutrophils
  • when you have a site of inflammation the neutrophils can leave the vascular system and migrate towards the site of inflammation
  • they go through a process where they align with the wall and roll along and squeeze there way through the endothelial wall and then migrate to the tissue
  • there are chemical mediators that are produced at the site of inflammation that are attracted to the phagocyte and work their way towards the chemical as a concentration gradient
  • then process of phagocytosis

. extravasation of leukocytes into tissues ( exudate )
. margination
. rolling
. diapedesis

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9
Q

describe the process of phagocytosis ?

A
  • phagocytes arrive at the site of inflammation by chemotaxis
  • phagocytes attach to microorganisms, cell debris or foreign material via surface receptors
  • material internalised and destroyed
  • phagocytosis is enhanced by the antibodies and the complement system of proteins ( opsonization )
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10
Q

what is the inflammatory response controlled by ?

A
  • controlled by inflammatory mediators
    examples include
  • vasoactive amines e.g. histamine , serotonin
  • plasma proteases e.g. complement, kinins
  • arachidonic acid and metabolites ( eicosanoids )
  • cytokines
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11
Q

what are the mast cell mediators ?

A
  • mast cell mediators include pre-formed and newly formed mediators
  • pre-formed mediators include : histamine , heparin and neutral protease
  • newly found mediators include leukotrienes ( LTD4, LTC4), prostaglandin D2 and platelet activating factor
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12
Q

what are the outcomes of acute inflammation ?

A
  • completer resolution
  • scar formation
  • progress to chronic inflammation
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13
Q

what is the ocular response to inflammation ?

A
  • redness- due to the vascular events, so blood vessels that are normally fine , suddenly dilate and everything becomes red
    redness can be diffused or localised
    e.g. episcleritis or acute closed angle glaucoma
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14
Q

what is episcleritis ?

A

episclera - which is one of the layers of the surface of the eye becomes inflammed

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15
Q

what is acute closed angle glaucoma ?

A
  • acute closed angle glaucoma - drainage angle for aqueous humour has become narrowed
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16
Q

what is another response to inflammation ?

A
  • oedema
    e. g conjunctival oedema

can be localised or diffused

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17
Q

what is another response to inflammation ?

A
  • exudate

. increased vascular permeability
. rich in protein
. rich in inflammatory cells

e.g. uveitis - proteins leak into the aqueous humour , proteins are big molecules which scatter light

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18
Q

what is another response to inflammation ?

A

cellular infiltration

e. g. bacterial keratitis - which is a bacterial infection of the cornea - which is a bacterial infection of cornea - you can see a circular white patch - which is a collection of inflammatory cells where bacteria are growing in that lesion and cells migrate to that lesion to stop the damage caused by the bacteria
- marginal keratitis - which is peripheral infiltrate

  • chalazion - where the meibomian glands within the eyelids become blocked and secretion starts to build up
  • cell type would depend if it was acute ( neutrophils) or chronic ( lymphocytes, macrophages )
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19
Q

what is another response to inflammation ?

A
  • discharge
  • eye can become watery
  • over production of mucous
  • sign of infection
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20
Q

what is another response to inflammation ?

A
  • conjunctival response
    e. g. formation of conjunctival papillae and follicles
  • papillae common in allergic eye disease
  • follicles characteristic of viral infection or toxic reactions
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21
Q

what are examples of inflammation of the posterior segment of the eye ?

A
  • anterior ischaemic optic neuropathy
  • optic disc isn’t receiving enough oxygen because blood vessels that supply oxygen to the disc have become blocked through an inflammatory response
  • sarcoidosis - is an example of chronic inflammation
22
Q

what is autoimmunity ?

A
  • autoimmunity represents the immune attack of normal body tissues
  • breakdown of self-tolerance
  • characterised by immune cell infiltration and inflammation of the target tissues
  • tend to be associated with particular HLA haplotypes
    e. g. HLA B27
  • ocular autoimmunity can occur in the presence or absence of systemic autoimmune disease
23
Q

what are examples of ocular autoimmune diseases in the absence of systemic involvement ?

A
  • moorens ulcer - cornea has become thinner and is at risk of breaking through - loss of corneal tissue
  • sympathetic ophthalmia - in damaging an eye certain antigens are exposed to the immune system, you then have immune cells that are directed to target that particular pathogens , you also get immune attack of normal healthy eye
24
Q

how are autoimmune diseases in the eye mediated ?

A
  • autoreactive T-helper cells ( CD4 ) are often responsible for initiating the tissue damage via the production of cytokines
  • autoreactive cytotoxic T cells ( CD8) can also cause tissue damage
  • autoantibodies cause tissue damage via a type 2 mechanism ( antibody-dependent cell killing )
25
Q

what are allergic eye disease caused by ?

A
  • caused by type I or type IV hypersensitivity reactions
26
Q

what is an example of type I hypersensitivity reaction?

A
  • acute allergic conjunctivitis

- seasonal allergic conjunctivitis

27
Q

what is an example of mixed type I and type IV reactions?

A
  • giant papillary conjunctivitis

- vernal

28
Q

what is an example of type IV reaction?

A
  • conjunctival medicamentosa
29
Q

what is cause of infection ?

A

bacteria , HSV ( herpes simplex virus ) , VZV ( varicella zoster virus ) , protozoa , fungi

30
Q

what pathogens cause infection in the uvea?

A
  • bacteria , CMV, VZV , protozoa
31
Q

what pathogens cause infection in the endophthalmitis ( affect the whole eye) ?

A

bacteria , fungi

32
Q

what pathogens cause infection in lids and conjunctiva ?

A

bacteria , chlamydia , HSV , VZV , adenovirus

33
Q

what pathogens cause infection in the orbital ?

A

bacteria

34
Q

what are certain risk factors that predispose to infection ?

A
  • immune status
  • ocular morbidity
  • contact lens wear
35
Q

what are peri-ocular infections ?

A

infections that affect the eye-lid , conjunctiva and lacrimal system

36
Q

what are example of peri-ocular infections in the eyelid ?

A
  • external hordoleum ( stye )- produce swelling of lid margin
  • canused by an infection of ciliary sebaceous gland ( Zeis)
  • typically caused by a bacterium staph. aureus
  • treated by topical antibiotics if needed
37
Q

what are pre-septal infection ?

A
  • infection of the superficial eyelid.
  • the inflammation remain confined to the sift tissue layers superficial to the orbital spetum and ocular function remains intact
38
Q

what are orbital cellulitis infection ?

A
  • infection of the soft tissues in the orbit posterior to the orbital spetum. usually occurs secondary to bacterial sinusitis
39
Q

why are orbital infections life threatening ?

A
  • direct communication between orbital and cranial cavity via the optic cannel
  • infections can track from orbit into the brain
40
Q

what is orbital septum ?

A
  • membrane that stretches from tarsal plate within the lid
  • holds back orbital contents
  • anything behind the orbital septum is an orbital cellulitis and is potentially serious
41
Q

why is it important to differentiate between pre-septal cellulitis and orbital cellulitis ?

A
  • anything behind the orbital septum is an orbital cellulitis and is potentially serious
  • this is because there is a - direct communication between orbital and cranial cavity via the optic cannel
  • infections can track from orbit into the brain
42
Q

why is it difficult to differentiate between pre-septal cellulitis and orbital cellulitis ?

A
  • because it affects children as examining children is difficult
  • most common in children
    75% < 5yrs
43
Q

what is the epidemiology of pre-septal and orbital cellulitis ?

A

pre-septal ( 94%) : orbital cellulitis ( 6% )

44
Q

how to diagnose pre-septal cellulitis/orbital infection ?

A

CT most helpful

45
Q

what is the treatment of pre-septal ?

A

antibiotics

46
Q

what is the treatment of orbital cellulitis ?

A

antibiotic / surgery

47
Q

what is conjunctivitis ?

A
  • most common eye infection
  • can be caused by virus , bacteria or chlamydia
  • viral conjunctivitis doesn’t have a drug that can treat it
  • not serious
48
Q

what is keratitis ?

A
  • infection of cornea
  • can be serious
  • can be caused by bacteria , virus , fungal , protozoal
49
Q

what is Uveitis caused by ?

A
  • infects the back, front or middle or all of uvea
  • usually autoimmune disease
    or no particular explanation
  • rarely infection
  • anterior uveitis - mostly caused by autoimmune
  • caused by HSV or VZV
  • posterior uveitis - 50% infectious and 50% autoimmune
  • caused by toxoplasmosis, toxocara, syphilis , CMV
50
Q

what is endophthalmitis ?

A
  • very serious
  • usually bacterial and acute
  • most cases exogenous
  • can happen after surgery / trauma

Neural Biology 1 (58 decks)

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