Dependence of radioactive iodine-131 capture by the lacrimal ducts on the tear production level

Purpose: Secondary acquired lacrimal duct obstruction (SALDO) is one of the complications of radioiodine therapy. SALDO is formed a few months after therapy if there is a sufficient uptake of radioactive iodine by the nasolacrimal duct. To date, risk factors leading to SALDO are unclear. The objective was to determine the correlation between the tear production level and radioactive iodine-131 uptake in the lacrimal ducts. Methods: Basal and reflex tear production was studied in 64 eyes prior to the therapy with radioactive iodine-131 after drug-induced hypothyroidism. The condition of the ocular surface was assessed using the Ocular Surface Disease Index (OSDI) questionnaire. Seventy-two hours after the radioactive iodine therapy, scintigraphy was performed, which determined the presence or absence of iodine-131 in the lacrimal ducts. T-statistics and the Mann–Whitney criterion were used to identify the differences between the groups. The differences were considered significant at P ≤ 0.05. The current tear production level in patients receiving radioiodine therapy was determined using a mathematical model. Results: A statistically significant difference between the basal (p = 0.044) and reflex (p = 0.015) tear production levels was found in cases with and without iodine-131 uptake by the lacrimal ducts. The probable current tear production level corresponds to the sum of basal and 10–20% of reflex tear production. The uptake of iodine-131 was found regardless of the OSDI results. Conclusion: The probability of iodine-131 uptake by the lacrimal ducts rises as the tear production level increases.