Allergic conjunctivitis

The patient with allergic conjunctivitis presents with: (1)

• intense itching
• conjunctival oedema
• apparent enophthalmos - the eyes sink into the surrounding oedematous tissue
• hyperaemia may be relatively mild
• allergic eye disease is generally seasonal

There are six recognised types of allergic conjunctivitis: (2)

• atopic
• seasonal
• perennial
• drug-induced
• contact lens-induced
• vernal

Management principles: (3)

• avoidance of allergen if known
• pharmaceutical management options include:
  • topical mast cell stabilisers (4)
    • for example sodium cromoglycate
      • use throughout a period of allergen exposure
      • newer agents (e.g. lodoxamide and nedocromil) may be effective in those with an inadequate response to sodium cromoglicate
        
        
  • topical antihistamines may be useful (4)
    • azelastine may also have additional mast cell stabilising properties
    • not a therapeutic option that is appropriate for prolonged use (no longer than six weeks)
    • not an appropriate treatment option in contact dermatoconjunctivitis
      
      
  • oral antihistamines such as loratadine or chlorphenamine may be used (1)
    • especially useful when there is associated allergic rhinitis
    • can cause drowsiness, especially the older compounds such as chlorphenamine - patients need to be cautioned regarding this
    • the newer-generation oral antihistamines are preferred because they are less sedating
      
      
  • in general, corticosteroid containing ointments or drops should be avoided unless the prescriber is able to monitor accurately for adverse effects e.g. glaucoma, cataract - and also should only be used if certain of the diagnosis of allergic conjunctivitis. Topical corticosteroids should never be initiated in primary care, and never be given for an undiagnosed red eye, if visual acuity is impaired, or if there is a previous history of ocular herpes simplex. (5)
    
    
  • diclofenac eye drops - these are licensed for seasonal allergic conjunctivitis (1)
  • intranasal corticosteroids have been shown to reduce ocular symptoms (6)

References:

1. Azari AA, Barney NP. Conjunctivitis: a systematic review of diagnosis and treatment. JAMA. 2013 Oct 23;310(16):1721-9
2. What sets vernal keratoconjunctivits apart form other allergic conditions, and how to create targeted treatments for it. Review of Ophthalmology, 2012
3. American Academy of Ophthalmology. Conjunctivitis preferred practice pattern. Nov 2018 [internet publication]
4. Castillo M, Scott NW, Mustafa MZ, et al. Topical antihistamines and mast cell stabilisers for treating seasonal and perennial allergic conjunctivitis. Cochrane Database Syst Rev. 2015 Jun 1;(6)
5. Bielory BP, Perez VL, Bielory L. Treatment of seasonal allergic conjunctivitis with ophthalmic corticosteroids: in Curr Opin Allergy Clin Immunol. 2010 Oct;10(5):469-77.
6. Origlieri C, Bielory L. Intranasal corticosteroids: do they improve ocular allergy? Curr Allergy Asthma Rep. 2009 Jul;9(4):304-10.