Assessment of conjunctivitis

Conjunctivitis is inflammation of the conjunctiva. It is a very common clinical presentation. There are numerous causes, including viral and bacterial infections, and allergy; viral conjunctivitis is most common and does not require antibiotic therapyWatson, 2018. Symptoms and signs can help to differentiate between the causes and avoid unnecessary use of antibiotics – see Comparative features of types of conjunctivitis. For indications for a conjunctival swab, see Indications for a conjunctival swab in patients with conjunctivitis.

Note: Most cases of conjunctivitis are caused by a viral infection and do not require antibiotic therapy.

Prompt referral to an ophthalmologist is required for conjunctivitis that is associated with severe or worsening symptoms (eg significant pain, reduced vision or photophobia) to exclude more serious diagnoses such as keratitis.

Note: Pain, reduced vision or photophobia require prompt referral to an ophthalmologist.

Table 1. Comparative features of types of conjunctivitisPrintable table
Type of conjunctivitis	Clinical features	Aetiology
Allergic conjunctivitis	symptoms are usually bilateral in seasonal and perennial conjunctivitis symptoms may be unilateral in contact hypersensitivity symptoms include itch, watery or mucoid discharge	local response to an allergen, including: seasonal (typically spring and autumn) perennial contact (eg preservatives in eye drops, contact lens solutions)
Bacterial conjunctivitis	acute onset of symptoms symptoms initially unilateral but can become bilateral symptoms include conjunctival injection (red eye), purulent discharge, crusting of the eyelids	can be primary or secondary (eg nasolacrimal duct obstruction) pathogens include Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae
Chlamydial conjunctivitis	acute or subacute onset of symptoms symptoms usually unilateral symptoms include conjunctival injection (red eye) and mucopurulent discharge may also be chronic conjunctivitis; see Trachoma	Chlamydia trachomatis
Gonococcal conjunctivitis	acute onset of symptoms symptoms are severe and include copious green hyperpurulent discharge, swollen eye lids ulceration and rapid perforation of the cornea and blindness can occur in neonates, usually presents in the first 2 to 5 days of life, and sometimes at birth	Neisseria gonorrhoeae
Viral conjunctivitis	symptoms initially unilateral but often become bilateral within days symptoms include conjunctival injection (red eye), watery or mucoid discharge, irritation	frequently associated with a viral upper respiratory tract infection and preauricular lymphadenopathy most commonly caused by adenovirus

Children aged 2 to 12 months with sticky eyes often have blocked lacrimal (tear) ducts rather than conjunctivitis, and the accumulated material is mucus from the tear film rather than pus. If the conjunctiva is not inflamed, treat as for Epiphora.

Indications for a conjunctival swab for Gram stain, culture, sensitivity and pathogen-specific nucleic acid amplification testing (NAAT) (eg polymerase chain reaction [PCR]) in patients with conjunctivitis include those outlined in Indications for a conjunctival swab in patients with conjunctivitis.

Figure 1. Indications for a conjunctival swab in patients with conjunctivitis

(CARPA), 2022 (RCPA), 2024 Azari, 2013 Drew, 2015

children younger than 2 months – request NAAT (eg PCR) for Chlamydia trachomatis and Neisseria gonorrhoeae

persistent eye discharge – perform bacterial and viral conjunctival swabs to identify atypical or resistant organisms

persistent conjunctivitis – perform bacterial and viral conjunctival swabs to identify atypical or resistant organisms; request NAAT (eg PCR) for Chlamydia trachomatis, adenovirus and HSV

recurrent conjunctivitis – perform bacterial and viral conjunctival swabs to identify atypical or resistant organisms

suspected chlamydial conjunctivitis– request NAAT (eg PCR) for Chlamydia trachomatis

suspected gonococcal conjunctivitis – request culture, Gram stain and NAAT (eg PCR) for Neisseria gonorrhoeae

conjunctivitis not responding to appropriate therapy – perform bacterial and viral conjunctival swabs to identify atypical or resistant organisms

Note:

HSV = herpes simplex virus; NAAT = nucleic acid amplification testing; PCR = polymerase chain reaction