Long-term impairment of the lacrimal glands after radioiodine therapy: a cross-sectional study
Impairment of the lacrimal glands after external radiation has been well documented, but there are only a few reports on the effects of radioiodine therapy on the lacrimal glands. Long-term effects of high-dose radioiodine therapy on tear secretion have not previously been studied. We investigated 175 eyes of 88 patients with a history of radioiodine therapy for thyroid carcinoma (68 females, 20 males; mean age 55±16 years, range 17–81 years) and compared them with a sex- and age-matched control group (n=39). All patients had been given at least 2.96 GBq iodine-131 (maximal administered activity 22.3 GBq 131I). An ophthalmological investigation was performed 64±71 months (range 3–317 months) after initial radioiodine therapy by a single ophthalmologist. Lacrimal gland function was evaluated with three different function tests. External eye morphology was considered, and detailed ophthalmological history-taking was performed. Patients with factors known to affect lacrimal gland function (contact lenses, autoimmune disorders, history of additional radiation exposure) were excluded from the study. A total of 81 patients (92%) had at least one abnormal function test indicating impaired lacrimal gland function. Schirmer's tear test was decreased (<10 mm/5 min) in 47 of the 88 patients and definitely abnormal (<5 mm/5 min) in 35 patients. A tear film break-up time of <10 s was found in 78 patients, and 62 patients had a definitely abnormal break-up time of <5 s. The lacrimal lipid layer was impaired in 43 patients. The function tests were all significantly altered in the study group as compared with the controls (P<0.005, P<0.001, P<0.001, respectively). Both subjective symptoms of dry eye (P<0.01) and changes in the external eye morphology (P<0.001) were significantly more prevalent in the study group. Our findings suggest that in the majority of patients, lacrimal gland function may be permanently impaired after high-dose radioiodine therapy. All three layers of the tear film are involved and there is a pronounced long-term effect on the tear film stability.