Nasal Ocular Reflexes Contribute to Eye Symptoms
Condition: Rhinitis, Allergic, Seasonal
MeSH terms: Rhinitis; Rhinitis, Allergic; Rhinitis, Allergic, Seasonal
Study type: Interventional

Summary: 
      Eye symptoms of tearing, redness and itching frequently occur in patients with allergic
      rhinitis or hayfever. The purpose of this trial is to study whether placing an allergen (a
      substance that causes allergies) directly in your nose can cause you to have eye symptoms as
      well as nasal symptoms.
    

Detailed description: 
      Symptoms of conjunctivitis (tearing, redness and itching) frequently occur in patients with
      allergic rhinitis. The pathophysiology underlying these symptoms remains to be elucidated.
      The symptoms probably arise via a combination of mechanisms including direct contact of
      natural pollen with the conjunctiva and reflex mechanisms originating in the nose.

      Pollen exposure can result from direct hand transfer of pollen to the conjunctiva or,
      conceivably, from the forceful blowing of air, containing nasal secretions with antigen, up
      the nasolacrimal duct. The latter mechanism would be considered extremely unlikely because of
      the location of the nasolacrimal duct under the inferior turbinate (the duct's location is in
      an area with little pollen exposure) and the considerable force of air needed to cause
      reverse flow in the duct. The latter would also be true for topically applied intranasal
      drugs reaching the conjunctiva via the nasolacrimal duct, whereas the administration of
      medications to the conjunctiva frequently results in these medications reaching the nose via
      the nasolacrimal duct.

      In support of direct contact of pollen as a source of ocular symptoms in patients with
      allergic rhinitis is the observation that pollen can be washed out of the conjunctiva on
      windy days, although the amount is 10 fold less than the amount of pollen recovered
      simultaneously from the nose. Additionally, beginning with Noon in the early 1900s, and
      subsequently shown by others, direct conjunctival challenges induce ocular symptoms. Thus,
      direct contact is a plausible explanation, but its relative contribution to eye symptoms in
      allergic rhinitis is unknown. Since topical intranasal steroids are known to reduce eye
      symptoms and the chance of them reaching the eye by systemic absorption or directly when
      administered intranasally are very slim, the investigators would postulate that direct
      allergen contact at the conjunctiva is a small contributor to the overall ocular symptom
      complex.

      Reflex mechanisms within the nose have been shown to occur universally in response to nasal
      challenge with antigen. Nasal challenge with antigen induces a reflex in the contralateral
      nasal cavity, known as the nasonasal reflex. This reflex can also be initiated by nasal
      challenge with cold, dry air and histamine. The contralateral response to antigen, cold dry
      air and histamine is blocked by topical anticholinergic agents applied to the contralateral
      side, suggesting that the efferent limb is parasympathetically mediated. Histamine is only
      released on the side of challenge with antigen but oral H1 antihistamines reduce the
      contralateral response to unilateral nasal allergen challenge, suggesting that histamine
      contributes to the initiation of the reflex. The eye is richly innervated by parasympathetic
      nerves which enter the eye after running in conjunction with the parasympathetic input to the
      nasal cavity. The investigators, therefore, hypothesize that the conjunctiva will respond to
      nasal allergen in a manner similar to the contralateral nasal cavity.

      Purpose: The investigators will study whether antigen-induced nasal reflexes cause eye
      symptoms. The investigators suspect that reflexes occur between the nose and the eye, and
      contribute substantially to eye symptoms in allergic patients during the allergy season. The
      investigators propose to demonstrate that nasal challenge with antigen leads to increased
      lacrimation.
    

Intervention name(s): Azelastine nasal spray
Intervention type(s): Drug
Intervention MeSH terms: Azelastine
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic
Keywords: allergic rhinitis