conjunctivitis%20-%20allergic,%20seasonal%20-and-%20perennial
CONJUNCTIVITIS - ALLERGIC, SEASONAL & PERENNIAL

Conjunctivitis is the inflammation of the conjunctiva.

Allergic conjunctivitis happens when the direct exposure of the ocular mucosal surfaces to the environment causes an immediate hypersensitivity reaction in which triggering antigens couple to reaginic antibodies (IgE) on the cell surface of mast cells and basophils, leading to the release of histamines that causes capillary dilation and increased permeability and thus conjunctival injection and swelling.
Seasonal allergic conjunctivitis is the most common form of allergic conjunctivitis in temperate climates. It usually occurs and recurs at a certain period of the year (eg summer).
Perennial allergic conjunctivitis manifests and recurs throughout the year with no seasonal predilection. It is most common in tropical climates.

Pharmacotherapy

Antihistamines (Ophthalmic)

  • Eg Emedastine, Levocabastine
  • Compete for the histamine receptor sites
    • In human conjunctiva, stimulation of H1 receptor mediates symptoms of pruritus while H2 receptor is involved in vasodilation
  • Reduce itching & vasodilation
    • Emedastine was shown to be more effective than Levocabastine in decreasing chemosis, eyelid swelling, & other signs & symptoms of seasonal allergic conjunctivitis
    • A selective H1 antagonist with no adrenergic, dopaminergic or serotonergic effect
  • Provides immediate ocular relief as compared to oral antihistamines
  • May be used as monotherapy or in combination with decongestants/vasoconstrictors in treating signs & symptoms of allergic conjunctivitis
    • Antihistamine with decongestant/vasoconstrictor should not be used for >2 weeks without medical advice
  • Should not be used for >6 weeks without medical advice
    • Prolonged use of antihistamines that are nonselective may cause ciliary muscle paralysis, mydriasis, & photophobia, especially when used by patients with lighter irides
    • May also cause angle-closure glaucoma particularly in patients who are at risk (ie history of narrow-angle glaucoma, patients with narrow angles)

Antihistamines (Oral)

  • May be used as adjunctive therapy for moderate to severe allergic conjunctivitis
  • Useful in cases accompanied by non-ocular allergies (eg allergic rhinitis)
  • Inferior to ophthalmic antihistamines primarily due to 1- to 2- hours delay from systemic administration to delivery to ocular tissues but has longer duration of action
  • More likely than topical antihistamines to cause side effects
    • May be associated with drying of mucosal membranes & decreased tear production, especially in patients with concomitant dry eye

Antihistamines/Mast Cell Stabilizers (Ophthalmic)

  • Eg Azelastine,Bepotastine besilate, Epinastine, Ketotifen, Olopatadine
  • Have both mast-cell stabilizing & antihistaminic activity
    • Bind to H1 & H2 receptors, stabilizes mast cell, & down-regulates inflammatory markers that affects early & late phases of the conjunctival allergic response
  • May be used for either acute or chronic diseases
    • Relieve acute symptoms (eg ocular itchiness & redness) & prevent recurrence of allergic conjunctivitis
  • Fast-acting, effective & generally well tolerated

Corticosteroids (Ophthalmic)

  • Should be given and supervised by an ophthalmologist
  • May be considered for use in the treatment of severe & chronic ocular allergy
    • Block inflammatory pathways that perpetuate the persistent & chronic forms of ocular allergy
  • May be used when patient’s symptoms have not responded to other agents
    • 1-2 weeks course can be added to antihistamine/mast cell stabilizers if symptoms were not controlled
    • Lowest potency & frequency that relieves the patient’s symptoms should be given
  • Should only be used for a short period of time (≤2 weeks)
    • Chronic use of topical steroids is associated with glaucoma, cataract formation, & infections of the cornea & conjunctiva
  • Inappropriate use in herpes simplex, fungal, & other viral or bacterial keratitis may cause complications that may threaten vision eg corneal melting, perforation, & scarring

Lubricants (Ophthalmic)1

  • Consist of saline solution combined with wetting & viscosity agents, which is used 2-6x/day as needed
    • Non-preserved formulations are recommended if will be used frequently to prevent allergic reactions secondary to preservatives
  • Assist in the removal & dilution of allergens that come in contact with the eye surface
    • Do not alter the pathophysiology of the disease but treat co-existing tear deficiency
  • Numerous lubricants that differ by class, osmolarity & electrolyte composition are available

Mast Cell Stabilizers (Ophthalmic)

  • Eg Cromoglicic acid, Lodoxamide, Nedocromil, Pemirolast
  • Inhibit degranulation of mast cells which limits the release of inflammatory mediators & platelet-activating factor
  • Used for prevention of symptoms & for conditions that are recurrent or persistent
    • Have slower onset of action as compared to antihistamines
    • Requires multiple applications everyday to show effects
    • Most useful in the seasonal management of chronic allergic diseases of the eye
  • Effects of Cromoglicic acid are evident 2-5 days after the initiation of the therapy with maximum improvement of ocular symptoms after 15 days
  • Usually given to patients with moderate symptoms, after an ophthalmic decongestant have been administered to provide immediate relief
  • Studies have shown that Lodoxamide is more effective than Cromoglicic acid in reducing eosinophil activation, & clinical signs & symptoms
  • Pemirolast was shown to specifically inhibit mast cell degranulation, preventing the release of chemical mediators like histamine
  • May also help in improving symptoms of allergic rhinitis
  • Generally well tolerated & may be used as long as needed

Nonsteroidal Anti-inflammatory Drugs (Ophthalmic)

  • Eg Ketorolac
    • Inhibits the activity of cyclooxygenase blocking the production of prostaglandins
    • Helps reduce ocular signs & symptoms like itching or conjunctival hyperemia
    • Do not mask ocular infections, affect wound healing or intraocular pressure, nor contribute to cataract formation
Vasoconstrictors (Ophthalmic)
  • Eg Naphazoline, Phenylephrine, Tetrahydrozoline
  • Sympathomimetic agents
  • Decreases vascular congestion & eyelid edema but do not affect allergic response
  • Usually used in combination with ophthalmic antihistamines
    • Have been shown to have synergistic effect
    • Based on studies, Naphazoline plus Antazolin or Pheniramine were comparable in decreasing the signs & symptoms of allergic conjunctivitis
  • Chronic use (>10 days) may cause conjunctivitis medicamentosa

Immunotherapy

  • Used in patients with atopic disorders like SAC, PAC, allergic rhinitis, or asthma
  • Desensitizes a patient against a specific allergen
    • However, ocular symptoms takes longer than nasal symptoms
  • Cyclosporine A limits type IV allergic response thereby reducing infiltration of eosinophils
  • Tacrolimus reduces action of T cells
    • Giant papillae & corneal lesions as well as total sign & symptom scores are reduced in refractory disease
  • Needs careful monitoring by a specialist
1Many ophthalmic lubricants are available. Please see the latest MIMS for specific formulations.

Non-Pharmacological Therapy

Identification of Trigger Factors
  • Trial of avoidance may identify antigens
  • Skin testing or allergen challenge may be useful for identifying specific problematic antigens but are rarely needed

Avoidance of Trigger Factors

  • Eg closing windows, filtering air, removing pets & stuffed toys, vacuuming & dusting regularly, etc
  • Mainstay of managing allergic conjunctivitis
  • Use of goggle-type glasses are recommended during pollen-flying period
  • Reduce or avoid use of contact lens during seasonal flare-ups
  • House mites are a common allergen & can be reduced by using dust mite-proof encasings on pillows & mattresses, & washing sheets in hot water
    • Washing clothes frequently & bathing before bedtime may be of help
  • Sensitive patients should attempt to limit exposure to outdoors during times of high pollen count or other allergen counts

Cold Compress

  • Causes vasoconstriction which can improve patient comfort by reducing itching
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