conjunctivitis

Introduction

bilateral red eyes tend to be more likely due to either conjunctivitis, welder flash burns - UV keratopathy (photo keratitis), or chemical burns, the latter two generally also cause keratitis

if only one eye is red, take special care to exclude other important pathologies - see acute atraumatic painful red eye(s)

conjunctivitis may be caused by highly contagious organisms such as adenovirus, Haemophilus influenzae, etc - wear gloves and wash hands!
- spread is usually via direct contact and indirect contact (eg. toys, door handles, etc)
- a person with infectious conjunctivitis will remain infectious as long as there is a discharge from their eye
  - children with infectious conjunctivitis should be kept home from child care, kindergarten or school until the discharge from the eyes has cleared¹⁾
  - regularly wash hands thoroughly to prevent the infection spreading to others
  - use a clean pillowcase and towel to use each day to prevent the infection spreading to the other eye if only one is affected
  - breastmilk used on the eyes does not treat conjunctivitis and there is no benefit to using it on your baby’s eyes
- in addition, respiratory viruses are spread by droplets / aerosol from sneezing or coughing
those who wear contact lenses should not use them until their conjunctivitis has cleared up

in Australia, pharmacists can prescribe and dispense chloramphenicol eye drops to those over age 2yrs - under 2yrs requires a doctor's script

usually present with bilateral itchy, mildly painful eyes with swollen, injected conjunctiva
visual acuity may be affected if there is a lot of tearing
infective causes generally start in one eye and spread to the other eye
bacterial causes tend to have a purulent discharge

adenovirus
respiratory viruses - common cold, influenza, COVID-19 coronavirus (2019-nCoV / SARS-CoV-2)
enteroviruses
picornaviruses

Staphylococcus aureus
- common in adults; spreads easily via skin-to-eye contact
Streptococcus pneumoniae
- frequently causes outbreaks among children
Haemophilus influenzae
- highly transmissible, especially in daycare and school settings
gonococcus
- esp. neonatal

hay fever sufferers often develop bilateral conjunctivitis
- in addition to exposure from allergens, symptoms will vary according to genetic makeup, with at least 34 genes identified to be associated with symptoms²⁾

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²⁾