The sodium pertechnetate Tc 99m content in the tears of 32 patients receiving intravenously administered pertechnetate Tc 99m for brain scan was studied. This study sought to provide a more quantitative measure than the Schirmer test of lacrimal secretory function. It also sought to determine the potential for scan artifacts due to pooling of radioactive tears.
Radioactivity of tear samples was determined. Results were expressed in terms of average total activity and average activity per volume, at various times after injection. Both sets of data had large standard deviations.
It was thought unlikely that Sjögren syndrome and other hypofunctions of lacrimation could be diagnosed by this method owing to the very low activity present in some presumable normal tears. Brain scan artifacts due to the extracranial accumulation of tears can be produced by the pooling of as little as 0.4 ml of tears.
O'Nan WW, Wirtschafter JD, Preston DF. Sodium Pertechnetate Tc 99m in Lacrimal Secretion. Arch Ophthalmol. 1974;91(3):187-189. doi:10.1001/archopht.1974.03900060195007