The association of radioiodine therapy for the treatment of thyroid cancer with nasolacrimal duct obstruction has been well documented in the medical literature. Prior case reports have documented radioactive iodine detection in the tears of patients following radioiodine therapy. It is possible that radioactive uptake by the cells in the lacrimal sac and nasolacrimal duct lead to inflammation, fibrosis, and obstruction of the tear duct over time. A recent study has shown that the administration of artificial tears decreases the level of detectable radioiodine in the tears of patients undergoing radioiodine therapy for thyroid cancer. The purpose of this study will be to assess whether administering tears after radioactive iodine therapy for thyroid cancer decreases the incidence of nasolacrimal duct obstruction in the two years following radioactive iodine treatment.