Background The allergic reaction taking place in the nasal mucosa can induce a secondary ocular (keratoconjunctival) response of an immediate (SIOR), late (SLOR) or delayed (SDYOR) type in some patients with keratoconjunctivitis (KC).

Objectives To investigate the concentration changes of histamine, tryptase, eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), eosinophilic peroxidase (EPO), leucotrienes (LTB_4, LTC₄, LTE₄), prostaglandins (PGD₂, PGE₂ and PGF_2α), thromboxane B₂ (TXB₂), myeloperoxidase (MPO), interferon-γ (IFN-γ) and interleukins (IL-2, IL-4 and IL-5) in tears during the SIOR, SLOR and SDYOR.

Methods 19 SIORs (p<0.001), 28 SLORs (p<0.001) and 10 SDYORs (p<0.05) recorded in 57 KC patients following nasal challenges with allergens (NPT) and 57 phosphate-buffered saline (PBS) control tests were repeated and supplemented with determination of the mediators in tears.

Results The ocular response types were associated with significant changes (p<0.05) of mediators in tears as follows: (1) SIORs: histamine, tryptase, ECP, LTC₄, PGD₂, PGF_2α, IL-4 and IL-5; (2) SLORs: histamine, ECP, EDN, LTB₄, LTC₄, PGE₂, MPO, IL-4 and IL-5; (3) SDYORs: LTB₄, TXB₂, MPO, IFN-γ and IL-2. No significant changes of these factors were measured in tears during the 57 PBS controls (p>0.1).

Conclusions These results demonstrate a causal involvement of nasal allergy in some KC patients, inducing a secondary keratoconjunctival response of an immediate (SIOR), late (SLOR) or delayed (SDYOR) type, associated with different inflammatory mediator profiles in the tears, suggesting participation of different hypersensitivity mechanisms. These results also emphasise the diagnostic value of nasal challenge with allergen combined with monitoring of ocular response in KC patients, responding insufficiently to the usual ophthalmologic therapy.