Purpose To investigate the effects of lacrimal drainage obstructions on the lacrimal gland activity and if there exists a potential link between the two.

Methods Direct assessment of the lacrimal gland activity from the palpebral lobe was performed in consecutive patients diagnosed with unilateral primary acquired nasolacrimal duct obstruction (PANDO), along with Ocular Surface Disease Index (OSDI), non-invasive tear break up time (NIBUT; Oculus K5M), tear meniscus height and Schirmer I. The primary outcome measure was the difference in the tear flow rate between the eye with PANDO and the contralateral uninvolved eye.

Results Thirty patients (median age, 45.5 years; 25 females) with unilateral PANDO had epiphora for a mean duration of 20 months. The mean OSDI score was 6.3. NIBUT (mean 11.56 vs 11.58 s; p=0.49) and Schirmer I values (mean 18.83 vs 19.4 mm; p=0.313) were not significantly different between PANDO and non-PANDO eyes. The morphology of the palpebral lobe (size 29.3 vs 28.6 mm², p=0.41) and the number of lacrimal ductular openings (median 2 vs 2.5) were similar between the two eyes. The mean tear flow from the lacrimal glands of the PANDO side was significantly reduced compared with the contralateral uninvolved side (0.8 vs 0.99 µL/min; p=0.014)).

Conclusion Tear flow rate from palpebral lobes of patients with unilateral lacrimal outflow obstruction shows a significant reduction compared with the contralateral side. The potential ways of communications between the tear drainage and the tear production mechanisms need to be explored further.