Effect of Lachrymatory Factor from Onion on Tear Secretion in Patients with Tear Deficient Dry Eye

Abstract

Abstract: : Background: Reflex tear secretion is known to reduce in tear deficient dry eye (TDDE). This study aimed to investigate the effects of synthesized onion lachrymatory factor (Thiopropanal S–Oxide) on reflex tear secretion in patients with TDDE. Methods: Enrolled were 16 patients with TDDE [15 eyes of 15 females and one eye of one male, aged 61.3±10.1 (mean±SD)]. Patients were classified into two groups according to the severity of dry eye [M group (10 eyes): mild to moderate dry eye; S group (6 eyes): severe dry eye]. Patients in M group had been treated only with eye drops and patients in S group had received punctal plugs both on upper and lower puncta. As control, six healthy volunteers [V group (six eyes): all males, aged 21.7±1.7] were enrolled. Their eyes were exposed to the 3µl lachrymatory factor instilled on to paper in a specially designed eyecup until their limit in endurance against irritation was reached (no longer than 60 seconds). After exposure, the following examinations were performed: 1) measurement of time until the feeling of irritation (TFI, seconds), 2) measurement of tear volume increase by measuring the increase in the tear meniscus radius (mm) [ΔR (t)=R (t minutes after the exposure, t=1 to 5, every one minute) – R (baseline)] using a video meniscometer (Yokoi, Cornea, 2000) at the central lower lid margin, and 3) scoring of ocular irritation [0 (none) to 4, according to the severity] once at the longest exposure and once more just after the end of examination. Results: TFI in M and S groups were 18.8±9.3 and 21.4±9.8, respectively, which were significantly longer (both p<0.05) than that of healthy eyes (9.8±1.5). Delta R (t) reached the maximum at Δ (2) [0.034±0.03 and 0.00042±0.04 in M and S groups, respectively and they were significantly smaller (p<0.05) than that in V group (0.25±0.14)] and the baseline at around Δ (5). Averaged scores of ocular irritation in M and S groups at the longest exposure were 1.8, and 1.7, respectively and they were significantly smaller (p<0.05) than that in V group (3), and all returned to 0 soon after the end of examination. Conclusions: The lachrymatory factor from onion could yield transient tear volume increase in patients with mild to moderate TDDE, but not in those with severe TDDE. This indicates the possible application of lachrymatory factor to tear secretion test or treatment for TDDE.

Keywords: cornea: tears/tear film/dry eye • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials • cornea: clinical science