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Vernal keratoconjunctivitis (VKC) is an allergic ocular disease in children and young adults. It is linked to atopy but it is characterized by typical inflammatory changes of ocular tissues. The conjunctiva often shows hyperplasia, with infiltration of lymphocytes and eosinophils; also mast cells, confined to the substantia propria in normal subjects, invade the epithelium in VKC. Both mucosal (MC(T)) and connective tissue (MC(TC)) types of mast cell can be found in the conjunctival tissues of VKC patients, whereas MC(TC) predominate in the normal eye. Much of the damage caused to the surface of the eye in VKC appears to be due to cytotoxic factors released from the invading eosinophils. Ongoing studies of cell/mediator interactions involved in the inflammatory process are contributing to the understanding of VKC and other allergic eye diseases also providing the rationale for effective treatment which may be found by blocking the immunological inflammatory network at specific points. Therapeutic studies with nedocromil sodium have shown encouraging results. For example, a six-week placebo comparison in Italy found nedocromil sodium eye drops to be efficacious in reducing hyperaemia, eye itching and inflammatory cells present in tears. Similarly, a four-week trial in Egypt showed this drug superior to sodium cromoglycate using the same q.i.d. regimen.

The purpose of this study was to describe the pattern of the ocular late phase reaction in patients with ocular hay fever. The authors monitored the clinical and cytological conjunctival response after topical allergen challenge. A conjunctival provocation test was performed in six ryegrass-sensitive patients and six healthy volunteers with 320,000 Biological Units (Pharmacia, Uppsala) of ryegrass antigen, diluted in albumin, in one eye; albumin diluent alone was used in the second (control) eye. Clinical symptoms were evaluated before challenge after 20 min, then hourly for 12 hours and 24 hours after challenge. Cell counts in the tear fluid were performed at the same time interval The results obtained show a significant clinical reaction during the entire period, differing in peaks in individual cases. This reaction was associated with a persistent inflammation, with neutrophils in the early phase and eosinophils and lymphocytes in the late phase period The data thus show that ocular challenge with high allergen doses induces clinical and cellular evidence of an ocular late phase reaction and suggest that the conjunctival provocation test may be used for a better understanding of the pathogenesis of mild but persistent ocular inflammation in ocular hay fever.

The authors report a series of conjunctival provocation tests in a single allergic patient indicating that tears collected during the late phase of a conjunctival reaction induced by allergen challenge, can act as inducers of a new late-phase reaction when applied again to the eye of the same patient. This short report is aimed at stimulating more extensive investigations to confirm the authors' observation and to prove the hypothesis here suggested that soluble mediators present in tears during the late-phase conjunctival reaction can act as inducers of a de novo recruitment of inflammatory cells.