conjunctivitis%20-%20allergic,%20seasonal%20-and-%20perennial%20(pediatric)
CONJUNCTIVITIS - ALLERGIC, SEASONAL & PERENNIAL (PEDIATRIC)
Allergic conjunctivitis is the direct exposure of ocular mucosal surfaces to the environment that 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.
Nerve endings are also stimulated causing pain and itching.
Seasonal allergic conjunctivitis is the most common form in temperate climates. It usually occurs and recurs at a certain period of the year and subjectively more severe than perennial allergic conjunctivitis.
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, Nedocromil
  • 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 and vasodilation
    • Emedastine was shown to be more effective than Levocabastine in decreasing chemosis, eyelid swelling, and other signs and 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 and 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, and 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)

  • Eg Cetirizine, Chlorpheniramine, Hydroxyzine, Loratadine 
  • 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 and decreased tear production, especially in patients with concomitant dry eye

Antihistamines/Mast Cell Stabilizers (Ophthalmic)

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

Corticosteroids (Ophthalmic)

  • Used for the treatment of severe and chronic ocular allergy
    • Block inflammatory pathways that perpetuate the persistent and chronic forms of ocular allergy
  • 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 and frequency that relieves the patient’s symptoms should be given
  • Relieve symptoms fast
  • Should only be used for a short period of time (≤2 weeks) and under the guidance of an experienced ophthalmologist
    • Chronic use of topical steroids is associated with glaucoma, cataract formation, and corneal/conjunctival infection
    • Lowest potency and frequency that relieves patient’s symptoms should be given

Lubricants (Ophthalmic)

  • Consist of saline solution combined with wetting and viscosity agents, which is used 2-6 times per day as needed
    • Non-preserved formulations are recommended if will be used frequently to prevent allergic reactions secondary to preservatives
  • Assist in the removal and 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 and electrolyte composition are available
  • Many ophthalmic lubricants are available. Please see the latest MIMS for specific formulations.

Mast Cell Stabilizers (Ophthalmic)

  • Eg Cromoglicic acid, Lodoxamide, Nedocromil, Pemirolast
  • Inhibit degranulation of mast cells which limits the release of inflammatory mediators and platelet-activating factor
  • Used for prevention of symptoms and for conditions that are recurrent or persistent
    • Have slower onset of action as compared to antihistamines
      • Effects of Cromoglicic acid are evident 2-5 days after the initiation of the therapy with maximum improvement of ocular symptoms after 15 days
    • Requires multiple applications everyday to show effects
    • Most useful in the seasonal management of chronic allergic diseases of the eye
  • 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, and clinical signs and 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 and 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 and 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 and 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 and symptoms of allergic conjunctivitis
  • Chronic use (>10 days) may cause conjunctivitis medicamentosa

Non-Pharmacological Therapy

Identification of Trigger Factors
  • Trial of avoidance may identify antigens
  • Skin testing or allergen challenge (serum antigen specific IgE antibody measurements) may be useful for identifying specific problematic antigens but are rarely needed

Avoidance of Trigger Factors

  • Eg closing windows, filtering air, removing pets and stuffed toys, vacuuming and 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 and can be reduced by using dust mite-proof encasings on pillows and mattresses, and washing sheets in hot water
  • 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

Immunotherapy

Principles of Therapy

  • Repeated administration of specific allergens in patients with IgE-mediated conditions to provide protection against allergic symptoms associated with exposure to these allergens
  • Only intervention that alters the natural history of allergic rhinoconjunctivitis
  • Activates regulatory T cells, thereby altering humoral response to allergens by increasing CD8+ T cells and IL-10, and reducing IL-13 production
  • Indicated for patients with the following:
    • Evidence of specific IgE antibody to allergen (positive allergy test results)
    • Any of the following:
      • Clinically diagnosed with both allergic rhinoconjunctivitis & asthma
      • Required medications
      • Poor response to avoidance measures
      • Adverse effects to medications
  • Initial dose should be performed in a medical facility by a trained personnel 
  • Recommended course is usually 4-5 years

Subcutaneous Immunotherapy (SCIT)

  • Efficacy is comparable to that of nasal glucocorticoids
  • Limited by frequent injection on regular basis and small risk of anaphylactic reactions

Sublingual immunotherapy (SLIT)

  • A more viable treatment compared to SCIT as self-administration is encouraged with this form
  • Use should be limited to those who can tolerate systemic reactions and its treatment 
  • Auto/self-injectable Epinephrine should be prescribed to all patients receiving SLIT
  • Has been associated with mild oral & GI symptoms & less risk for anaphylaxis compared to SCIT
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