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Repeating KHIO 1 > 7 Contact lens infections > Flashcards

7 Contact lens infections Flashcards

1
Q

Microbial/infectious keratitis:

A

Inflammation of cornea by bacteria, fungus, protist
Often following CL wear/corneal damage

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2
Q

Microbial keratitis risks:

A

CL overnight/extended wear
Inadequate hygiene
Ocular/systemic disease (diabetes/mellitus)
Extended corticosteroid use
Surgery / trauma

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3
Q

Acanthamoeba keratitis:

A

Rare protist corneal infection
Present in air, soil, fresh/tap water, hospital equipment, chlorinated pools
80% from CL wear (night/extended/submerged)

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4
Q

Acanthamoeba structure:

A

The ancan. Trophozoite has amoeboid shape with spike acanthopodia

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5
Q

Acanthamoeba protist survival:

A

Phenotypic switch into cyst form withstands environment (feeding /replication stage)
Extreme conditions (antimicrobials) > double walled cyst (no metabolism)
Difficult treatment

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6
Q

Acanthamoeba keratitis clinical presentation:

A

Extreme pain, redness, epiphora, FBS, photophobia
Progression > ring infiltrates (inflammtory in stroma) > Corneal ulceration /stromal abscess > enucleation

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7
Q

Acanthamoeba pathogenesis:

A

Adhesion to cornea epithelium
Cytopathic desquamation of epithelium > bowman’s penetration
Stromal invasion via collagenolytic enzyme
Neuritis (focus nerve damage)

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8
Q

Acanthamoeba adhesion

A

Binding to mannose glycoproteins via adhesin expressed on trophozoite mannose-binding protein
Abrasion / CLs increase mannose expression

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9
Q

Acanthamoeba Cytopathic effect

A

Cytolysis, phagocytosis, apoptosis of corneal epithelium
Inhibition of proteins > increase Ca channel activity

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10
Q

Acanthamoeba Stromal invasion:

A

Collagenolytic enzyme (serine/MMPs) release, damage collagen type 1
Causes corneal lesions, stromal ring infiltrates

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11
Q

Acanthamoeba treatment:

A

Topical drug cocktail against cysts
Biguanides (polyhexamethylese: PHMB) + diamidines (Hexamidine)
Hourly 0.2% of each then tapered

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12
Q

Mycotic keratitis

A

Corneal fungal infection of damaged epithelium
Filamentous (tropical): Fusarium
Yeast like (temperate): Candida

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13
Q

Mycotic keratitis risks:

A

CLs, Agriculture, defective eye closure, systemic diseases (diabetes)

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14
Q

Mycotic keratitis clinical presentation:

A

Abrupt pain, photophobia, discharge, blur, ulcer, feathery satellite infiltrates
IOP increase from iris fungal mass

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15
Q

Mycotic keratitis mechanism:

A

Adhesion to damaged epithelium via adhesins
Invasion past immune via fungal load
Morphogenesis to evade antimicrobials
Toxigenicity via mycotoxin production

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16
Q

Mycotic adhesion

A

Adhesins bind to cells/glycoproteins via mannoprotein
Glycoproteins upregulation by epithelium damage

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17
Q

Mycotic keratitis treatment:

A

Chemotherapy (topical + systemic)
Antifungals:
Polyenes (Natamycin)
Azoles (Triazoles)
Fluorinated pyrimidines (Flucytosine)
Dangerous in developing countries

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18
Q

Bacterial keratitis:

A

90% of microbial keratitis, mainly from CLs
Caused by Pseudomonas aeruginosa (most common), Strep p. (ulcer in developing countries), Staph a. , serratia

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19
Q

Bacterial keratitis clinical presentation:

A

Pain, redness, photophobia, ulceration
Ring infiltrates
IOP increase / glaucoma

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20
Q

Bacterial keratitis mechanism

A

Adhesion via adhesins
Invasion via proteases
Cytotoxic cornea damage
Stromal Necrosis and ring infiltrates

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21
Q

Bacterial keratitis adhesion:

A

Flagella mobilize microbe (non-virulent without)
Pili / Fimbriae > bind damaged epithelium carbohydrates/proteins
Staph a. > MASCRAMMS bind to collagen

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22
Q

Bacterial keratitis invasion

A

Exotoxin proteases degrade basement membrane
Metalloprotease and immune stimulation > RO presence
P Aeru. Contains many proteases which melt cornea

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23
Q

Bacterial keratitis drug treatments:

A

Broad spectrum antibiotics
Analgesics for pain
Cycloplegics for ciliary spasm
Antiglaucoma for IOP
Therapeutic CL for ulceration
Avoid NSAIDs (risk corneal melting)

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24
Q

Bacterial keratitis antibiotic treatments:

A

Broad spectrum antibiotics > Fluroquinolone mono/combination therapy
Aminoglycosides > gram-neg
Cephalosporin > gram-pos
Fluroquinolones > both bacteria via DNA/topisomerase inhibition

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25
Q

Bacterial keratitis treatment procedure:

A

Broad-spec antibiotics every half hour for a day
Severe cases use loading doses 5 minutes for 30 minutes

26
Q

Innate defences of cornea:

A

Tears > lactoferrin/lysozyme, immunoglobins (IgA/G), filtration
Epithelia > Cytokine secretion (IL-a) on damage > immune response
Keratocytes > IL-6 synthesis > anti-microbial / healing
Corneal nerves > sensory reflex via substance P/Calcitonin > IL-8 > Neutrophils
Complement > Protein cascade in limbus
Interferons (IFN) > Antiviral proteins

27
Q

Interferon corneal defence:

A

IFN-a from leucocytes
IFN-b from fibroblasts
IFN-y from T/NK cells
MHC assist IFNs
IFN-a/b activate NK cells to target viral cells

28
Q

Cells of innate immunity:

A

Neutrophils
Eosinophils
Macrophages
NK cells

29
Q

Neutrophils:

A

Pass endothelial cells via diapedesis (adhesion receptors on endothelum)
Phagocytoses microbes

30
Q

Eosinophils:

A

With IgE receptors and complement components
Activated via IL-3/5 > granulation

31
Q

Macrophages in corneal defence:

A

Phagocytic / antigen presenting / Cytokine secretion

32
Q

NK cells in corneal defence:

A

Large granular lymphocytic cells without antigen receptors
Recognize MHC1 > inhibition
Lyse cells poorly expressing MHC
Secrete TFN-a / IFN-a

33
Q

Cells of acquired immunity

A

Langerhans cells
Cytokines

34
Q

Langerhans cells of cornea:

A

Antigen presenters with MHC-2/1 antigens in limbal cornea
Recognize nonself antigen > processed > MHC transport to surface > T cell activation
MHC1 > CD8+ Cytotoxic T cell (kill microbe)
MHC2 > CD4+ T Helper cell (secrete cytokines)

35
Q

Cytokine release in cornea:

A

TH1 > IL-2 / IFN-y, IgG/M/A synthesis
TH2 > IL-4/5, IgE synthesis

36
Q

Immunologic differences from limbus to central cornea:

A

Peripheral: Langerhans / IgM / C1 (complement cells)
Antigen-antibody complexes activate complement easier in periphery

37
Q

Immune response to pseudomonas aeruginosa:

A

Bacterial lipopolysacchride (LPS) presence > Toll receptor 4 activation > Platelet adhesion molecule > increased diapedesis of neutrophils

38
Q

Contact lens complications:

A

Hypoxia
Microbial keratitis
Allergic / Toxic reaction
CL DED/Discomfort
CL-induces papillary conjunctivitis
Mechanical damage

39
Q

Corneal oxygen supply with CLs:

A

Disrupts O2 (Dk/t) / nutrient flow from tear film
Disrupts tear flow
Exacerbated by poor fit/extended wear

40
Q

CL Hypoxia induced changes:

A

Ocular/limbal erythema (redness)
Stromal oedema, vascularization, epithelial thinning, endothelial polymegethism (change in cell size), weakened immune defence.

41
Q

Treatment for CL hypoxia:

A

Silicone hydrogel / rigid gas-permeable CL change
Intermittent wear, CL discontinuing

42
Q

Inflammatory CL changes/clinical presentation:

A

CL infiltrative events (CIE)
Contact lens-induced red ere (CLARE)
Pain, photophobia, keratitis, peripheral ulcers

43
Q

Risk of non-infective CL inflammation:

A

30 day extended wear, Silicone hydrogel CLs, poor eye closure, tight lenses
Smoking > Infiltrates
Toxicity from CL solution

44
Q

Non-infective CL inflammation treatment:

A

Self resolving in 21 days after cessation
Corticosteroids / antibiotics increase speed
CL hygiene education

45
Q

CL induced papillary conjunctivitis (CLPC) types:

A

Local > CL too thick > chemotactic factor release > inflammatory response
Generalized > denatured tear film > lens deposits > antigenic stimulus

46
Q

CL induced papillary conjunctivitis CLPC risks:

A

Soft CLs (silicone-hydrogel)
Mechanical stimuli from poor CL fit
Long term wear > accumulation of lens deposits

47
Q

Cl induced papillary conjunctivitis (CLPC) clinical presentation:

A

Papules, palpebral conjunctival erythema (redness)
Itching, mucus discharge

48
Q

CL induced papillary conjunctivitis (CLPC) treatment:

A

Daily CL change
Hydrogen peroxide CL solution
Enforce rinse-rub cleaning
Topical mast cell stabilizers / antihistamines > steroids
Cessation of CLs

49
Q

Allergic / Toxic reaction to CL pathophysiology:

A

Uptake of small molecules from hydrogel material and CL solution > immune response

50
Q

Manifestations of allergic / toxic CL reaction:

A

Toxic keratitis / conjunctivitis with conj. Hyperemia, corneal irritation/infiltrates
Pain, CL intolerance, photophobia, tearing
Leads to Limbal stem cell deficiency (LSCD) and limbal corneal staining (after 2-4h)

51
Q

Causes of allergic / toxic CL reaction:

A

Irritate / cause LSCD / Stain limbal cornea
Preservatives (Thiomersal)
Overnight wear/hypoxia

52
Q

Definition of CL related discomfort and dryness

A

Episodic or persistent adverse ocular sensation related to lens wear
Symptoms must subside after cessation, unlike DED

53
Q

Physical clinical signs of CL related discomfort/dryness:

A

Lid wiper epitheliopathy and lid parallel conj. Folds

54
Q

Lid wiper epitheliopathy

A

CL friction on blink > palpebral conj. Irritates > abrasion on blink with ocular surface/CL > lissamine stain parallel to marx’s line (lid rim facing eye)

55
Q

Lid parallel conj. Folds

A

Bulbar conj. Stretching and folding at lower lid margin
At 4 and 8 o’clock on bulbar conj.

56
Q

CL wear and dry eye

A

12 fold risk factor, 50% CL users experience EDE symptoms
Caused by meibomian blockage via mechanical trauma

57
Q

Treatment of CL related discomfort/dryness

A

EDE treatment > lipid lubricant, lid hygiene, compress, suppliments
Without EDE > Daily CL change, non-preseritive solution, manage Demodex

58
Q

Mechanical changes with CLs:

A

Blinking / eye rubbing / CL dislocation / insertion / removal / CL damage
Long term wear > Corneal sensitivity loss (with low O2)
Sup. Epithelial arcuate lesions (SEAL) > upper cornea lesion
Corneal warpage from poor fitting hard CLs

59
Q

CL microbial keratitis epidemiology and risk

A

Risk increases 80 fold, 2-5 per 10000 users
10% with MK lose 2 lines of vision
Smoking, poor hygiene, unlicensed lens use

60
Q

Treatment of CL microbial keratitis:

A

CL cessation, broad spectrum antimicrobials, cycloplegics (synechiae prevention), doxycycline (corneal melting prevention)

61
Q

Types of microbes in CL related microbial keratitis:

A

Bacterial > most common Pseudomonas sp.
Fungal > commonly in tropical and agriculture
Acanthamoeba > Protozoan in water

Repeating KHIO 1 (15 decks)

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