26 Infections of the eye Flashcards
Eye divided in to 4 layers -
- conjunctiva
- cornea
- vitreous humour
- retina
Surface of eye exposed to external environment, so at risk of infection. Eyelids also create warm, moist environment. Conjunctiva is hot spot. Eyelids and tears are main protection, so any damage to this increases risk of infection
Conjunctivitis can be caused by bacteria or viruses.
What are most common bacterial causes?
Most common -
S aureus
S pneumoniae
H influenzae
Chlamydia trachomatis
Neisseria gonorrhoea - infection of newborn via birth canal
Bacterial tends to have purulent discharge, with no systemic features. Require treatment to improve quicker
Chlamydia/ gonorrhoea/ HSV always require treatment
Other bacteria can be self-limiting
Conjunctivitis can be caused by bacteria or viruses.
What are most common viral causes?
Viruses cause 90% of infections
- Adenovirus - most common
- Measles - via bloodstream
- HSV - reactivation of opthalmic division of trigeminal ganglia cuases corneal lesion
- VZV
- Enterovirus 70 - acute haemorrhagic conjunctivitis
- Coxsackie A24 - acute haemorrhagic conjunctivitis
Invade superficially, via blood, or via nervous system
Viral tends to have watery eye, with systemic features viral illness. No treatment required, except for HSV
Chlamydia trachomatis has specific surface molecules for binding to conjnctiva. Causes inflammation of eye-lids, which scars and contracts lids, which then pulls back eye lashes which grow inwards. This causes abrasion of cornea and blindness
Tyes A/ B/ Ba/ C - trachoma
Types D-K - inclusion conjunctivitis
200 million people worldwide affected by trachoma, with 2 million visually impaired
What is transmission method?
Via contaminated flies, fingers, towels
Due to poor hygiene, preventing regular washing of hands/ face
Some chlamydial strains can infect urogenital tract, as well as conjunctiva.
Newborn infaant can have conjunctival/ pulmonary infection with chlamydia
How to diagnose chlamydial eye infections?
What is prevention/treatment?
Usually clinical if endemic area
Chlamydia PCR
Topical or oral antibiotics e.g azithromycin, doxycycline
Improved sanitation - fly control
What infections are infants at risk of during birth?
S aureus
Neisseria gonorrhoeae - opthalmia neonatorum
Chlamydia
What disease is associated with wearing contact lenses?
Acanthamoeba can multiply in unchanged lens cleaning fluid
What is treatment for HSV dendritic ulcers?
Can be easily seen on fluorescein dye staining
HSV dendritic ulcers can lead to corneal scarring and neovascularisation, resulting in sight loss
Aciclovir/ famciclovir
Steroids
Corneal transplant
Infection of deeper layers of eyes can occur. trauma to eye can facilitate this.
What are bacteria/ viral causes of deeper eye infections?
Pseudomonas - foreign body/ trauma
CMV - chorioretinitis. Infection in utero/ immunocompromised
Rubella - cataracts/ micropthalmia. Infection in utero
Chorioretinitis is inflammation of choroid (thin vascular coat of eye) and retina
What are protozoal causes of deeper eye disease?
Hydatid disease - disruption of eye by growth of larval tapeworm in cyst
Loaisis
Onchocerca - chorioretinits
Taenia solium - chorioretinitis
Toxocara canis - chorioretinits
Toxoplasm gondii - chorioretinitis
How is toxoplasma chorioretinitis transmitted?
Ingestion of oocysts by infected cat faeces or eating meat contaminated by tissue cysts
- Pregnancy - tachyzoites cross placenta. Can invade eyes and all of CNS
- Reactivate in immunosuppressed
- need clinical suspicion i.e neonate or immunosuppressed patient. Check IgG levels, but does not confirm active infection.
How is onchocerca transmitted?
Called river blindness as flies develop in fast flowing rivers
Simulium flies which take up microfilariae larvae from skin of infected hosts, and reintroduce the larvae after they have fully developed to become infective
Adult worms live in subcutaneous nodules, and are usually harmless
Larvae mgirate through subcutaneous tissue, and can invade eye
What is treatment/ prevention of onchocerca?
Ivermectin
Vector control
Blindness is irreversible
What is presentation of ocular shingles?
Affected individuals typically present with unilateral pain with lesions on the forehead
and periocular area. Cutaneous vesicles at the side of the tip of the nose (Hutchinson’s
sign) indicate nasociliary nerve involvement and a greater likelihood that the eye will be
affected, although eye involvement can still occur without this sign.
Ocular involvement includes the following: Mucopurulent conjunctivitis
Associated with lid vesicles
Usually resolves within one week
May be associated with a secondary bacterial conjunctivitis
Episcleritis
Scleritis
Keratitis
How to diagnose ocular shingles?
Clinical diagnosis often
Swab for viral PCR
Treatment ocular shingles?
Aciclovir 800mg 5xday, for 7 days
Prednisolone accelerates rate of skin healing lesion, but does not affect outcome. Can give 40mg OD 7 days
