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Quantitative lacrimal scintillography, using 99mTc sulphur colloid, a high resolution gamma camera, and quantification using a digital computer, is a highly effective way of assessing lacrimal physiology, and of establishing normal flow and drainage values against which pathological cases may be compared.

• In a study of 100 asymptomatic lacrimal systems, we have found that quantitative lacrimal scintillography provided a sensitive and reproduceable test of canalicular function. This technique, at the present time, appears to have no role in the clinical evaluation of tear passage through the nasolacrimal duct to the nose. A revision of the currently accepted theory of lacrimal drainage is proposed. Lacrimal drainage is best approached as a bimodel system. The first part, from conjunctiva to lacrimal sac, is dependent upon the "lacrimal pump." The second part, by which tears drain from the sac to the inferior meatus of the nose at basal tearflow levels, is dependent on gravity and the resistance of the nasolacrimal duct.

Using a gamma camera and specially developed micropinhole collimator, the dynamics of the lacrimal drainage apparatus in man were studied in vivo with a radioactive tracer for the first time. Because of the much lower dosage of radiation and the more physiologic nature of demonstrating the lacrimal apparatus, this technique is suggested as an adjunct or replacement for the radiopaque dye studies (dacryocystogram). This first reported use of microscintigraphy suggests applications in other medical disciplines.

Epiphora is commonly caused by a relative or complete occlusion in the lacrimal drainage system (LDS), principally a nasolacrimal duct obstruction (NLDO). Dacryoscintigraphy (DSG), an extensively assessed imaging technique in diagnosing its abnormalities, can provide only planar images, according to which it needs to be improved. Our aim was to evaluate clinical utility of simultaneous DSG and single-photon emission computed tomography/computed tomography (SPECT/CT) combined with computed tomographic dacryocystography (CT-DCG) in the evaluation of LDS. Dynamic imaging with DSG was performed, and tracer radioactivity was detected by a gamma camera. Successively, SPECT/CT images of the involved region were gained, followed by CT-DCG, during which a contrast medium was syringed into the affected LDS, and finally contrast CT scans were obtained again from the same region. Fifty-seven patients, mean age 54.25 (± 18.26) years all with unilateral NLDO and 32 control subjects, all with patent LDS, mean age 49.88 (± 18.61) years were evaluated in the study. Delayed outflow of tearing eyes was exposed to DSG compared to the fellow and control eyes. The highest value for sensitivity was observed for SPECT/CT, followed by CT-DCG and DSG techniques, while combining DSG with SPECT/CT, DSG with CT-DCG, and SPECT/CT with CT-DCG, the sensitivity increased to 96.49%, 92.98%, and 94.73%, respectively. Although DSG is a sensitive nuclear medicine method, it only provides useful clinical data when simultaneously supplemented with SPECT/CT and CT-DCG trials as they jointly can offer valuable information about the localization of an abnormality and verify stenosis or obstruction.