Methods: 63 adults with ocular symptoms (itching, red eyes or tearing) were selected and tested for allergy to house dust mites and grass pollen by skin prick tests (ALK Abelló) and serum specific IgE (Immunocap-Phadia). They were considered atopic if these tests were positive to at least one allergen and non atopic if tests were negative. HCPT with 10-fold serial diluted glucose solutions was performed in all subjects until it produced conjunctival redness. Digital images were analyzed by two investigators (MD and technician) registering redness of the challenged eyes in red and the total area of contra-lateral eyes in blue using the fine brush tool (software GIMP 2.6.5). The number of red dots of the affected eye (%) was compared to the number of blue dots of the control eye.
Results: TPCH was positive in 33/38 atopic subjects (87%) and in 4/25 non atopic (16%). Most reactions occurred at the 40% glucose solution. Sensitivity was 87% and specificity 84% (p<0.0001). There was a significant correlation (96.5%, Pearson, p<0.0001) between the number of red dots reported by investigators in 23 digitalized images.
Conclusions: TPCH identifies CHR in both atopic and non atopic subjects. Atopic subjects exhibit CHR more frequently than non-atopic subjects. Digital images may be useful for grading ocular hyperemia in TPCH.