W7 keratitis

Question 1

Ocular defences:

Answer 1

Lids: physical/flushing
Tear film: IgG/A, lactoferrin, lysozyme
Cornea epith.: immunoglobins (IgG/A) defer microbe adhesion
Mucin: trap microbes
Innate immune: complement protein system
Tight junctions: prevent passage

Question 2

CL risk of keratitis:

Answer 2

1/proportional to Dk/t value
Least with RGP lenses
From hypoxia reducing epithelial adhesion > CLARE > keratitis
Usually gram- psuedomonas aeruginosa

Question 3

Antigen-antibody immune response:

Answer 3

Pathogen recognition > neutrophil/machrophage influx > bacterium phagocytosis > stromal infiltrate
Bacterial proteases degrade stroma > stromal loss > corneal perforation

Question 3

Risk factors for keratitis:

Answer 3

CLs
Sx/trauma
DED/bleph
Co-infection (acanthamoeba/HSV)
Blink dysfunction
Immunosuppression
Immune loss (DM/malnutrition)

Question 4

Signs/symptoms of bacterial keratitis:

Answer 4

Pain: severe / increasing
Epithelial defect: boggy edges (stromal oedema)
Discharge: mucopurulent
Ant. Chamber response: hypopyon
Location: central, away from limbal vessels
Size: larger than 2mm

Question 5

Fungal keratitis types:

Answer 5

Mold (filamentous): fuscarium, aspergillus
Yeast: candida albicans

Question 5

Management of bacterial keratitis:

Answer 5

Fluoroquinolone mono w/ciprofloxacin 0.3%
Q10m for first hour > qhour for 24h > review > qhour for 24h > q2hour
Unresponsive/complex needs referal

Question 5

Acanthamoeba patho:

Answer 5

Corneal epith. irritation > mannose glycoprotein upregulation > Acan. trophozoites adhere via acanthapodia > protease MIP133 release > epith. Cytolysis > stromal invasion / degregation
Immune neutro/macro. Influx > immune proteases > ring infiltrates
Acan. Cluster nerves > immune/anti-microbial response > form dormant cysts

Question 5

Fungal keratitis risks

Answer 5

Trauma (esp vegetables)
Biogel formation
Tropical climate
Immunosupression
Hydrogel CLs

Question 6

Acanthamoeba keratitis risks:

Answer 6

Present in water sources
Poor CL use > biofilm build up
Secondary to damage/HSV

Question 6

Acanthamoeba treatment:

Answer 6

Cease CLs and see ophthal.
Cocktail of polyhexamethylene biguanide (PHMB) with chlorhexidine 0.02% or Brolene 0.15% tapered from hourly>quaterly from 2-6 months

Question 7

Symptoms of acanthamoeba keratitis:

Answer 7

FBS
Severe Pain
Hyperemia
Epiphora
Epitheliopathy > Stromal radial infiltrates
Ant. Chamber inflammation

Question 7

Fungal keratitis patho:

Answer 7

Ahesion following epith. Dysfunction > proteolytic enzyme release > epith. Necrosis > stromal collagen dissolution
^size > poor neutophil phagocytosis
Usually present with bacterial co-infection

Question 8

Symptoms of fungal keratitis:

Answer 8

Filamentous: feathery infiltrates > ant. Chamber reation (hypopyon)
Yeast: Button infiltrate > epith. Ulcer

Question 9

HSK treatment:

Answer 9

Self limiting in 3w
Aciclovir 3% ointment 5/day for 2w minimises scarring

Question 10

Fungal keratitis treatment:

Answer 10

Ophthal referal
Topical natamycin 5% per hour for 24h then qid for months
Paired BS antibiotics prevent co-infection
Never steroids (increase fungal replication)

Question 11

Symptoms of HSK:

Answer 11

FBS, photophobia, epiphoria, blur, hyperemia
desensitisation
Dendritic lesion
IOP increase (trabeculitis)
Lid HSV vessicles

Question 12

HSK corneal lesion:

Answer 12

Small opaque epith. Cells > desquamation of central cells > punctate erosions progress/branch
Terminal bulbs contain swolen virus laden cells.
NaFL stains central desquamation
Lissamine stains damaged bulbs

Question 13

HZO keratitis process:

Answer 13

Varicella zoster initial infection (chickenpox) > rash, flu, pneumonia
VZV moves to dorsal root and cranial nerve ganglia (retrograde transport)
Reactivation > shingles(skin) / HZO(CNV1)

Question 14

HZO symptoms and treatment:

Answer 14

Punctate epith. Keratitis
Skin rash (nose)
Aciclovir 800mg 5/day for 10d

Question 15

CL complication patho:

Answer 15

Dt/k more than 87(overnight) or 24(daily) > Poor O2 diffusion > hypoxia > anaerobic metabolism > ATP decrease / lactic acid increase > pH decrease / ion pump loss > oedema / immune loss

Question 16

Symptoms of CL edema (hypoxia):

Answer 16

Acute:
Pain, blur, photophobia, tearing
Diffuse epithelial superficial keratopathy
Chronic:
No pain, light blur, endoth. Blebs.
Corneal neovasc:
Vessel presence

Question 17

CL associate dry eye patho:

Answer 17

CL causes pre-corneal tear film instability > PCTF disruptions > tear thinning > mucin increase > tear osmolarity
Poor CL hydration > dehydration

Question 18

CL keratopathy staining:

Answer 18

Scattered dots: Dot toxicity
Superior (epith. Arcuate) lesion: tight lid hyopxia (SEALs)
Diffuse spread: CL overwear
3/9 ‘oclock: RGP poor size

Question 19

Tight lens syndrome:

Answer 19

CL drying > tightening > ocular ahdereance > impaired tear flow > circulation loss > hypoxia with epith. Loss