The typical procedure involves use of
Technetium-99mcolloid, or in some cases
pertechnetate. The colloid is prepared with an activity of approximately 20
megabecquerels in 1
millilitre (ml). Patients place their head in a support and chin rest and a single drop of 0.01 ml is delivered to each eye. Imaging with a
gamma camera commences immediately, with a number of images acquired over 15 minutes.[1][2]
DSG allows
quantification of tear turnover and drainage.[4] Various quantification models have been developed, which must account for the variable drainage of
asymptomatic systems.[5] Some drugs administered to the eye via
eye drops, such as
beta blockers for
glaucoma, can be hazardous if quickly drained and absorbed through the
nasolacrimal duct. DSG is considered the best method to quantitatively assess the proportion of the dose drained in this way.[6] It can also be useful in assessing functional problems, where the lacrimal system appears unobstructed, and for
post-operative progress.[7][8]
Advantages of DSG over
dacrocystography include better functional information and a lack of
injection.[9] DSG does not provide precise localisation and may not be useful in cases of complete obstruction.[10]
^Tomlinson, Alan; Khanal, Santosh (April 2005). "Assessment of Tear Film Dynamics: Quantification Approach". The Ocular Surface. 3 (2): 81–95.
doi:
10.1016/S1542-0124(12)70157-X.
PMID17131012.
^Wilson, Clive G (August 1999). "Assessing ocular drug delivery with lachrimal scintigraphy". Pharmaceutical Science & Technology Today. 2 (8): 321–326.
doi:
10.1016/S1461-5347(99)00176-5.
PMID10441276.
^Chan, WengOnn; Malhotra, Raman; Kakizaki, Hirohiko; Leibovitch, Igal; Selva, Dinesh (September 2012). "Perspective: what does the term functional mean in the context of epiphora?". Clinical & Experimental Ophthalmology. 40 (7): 749–754.
doi:
10.1111/j.1442-9071.2012.02791.x.
PMID22429759.
S2CID20761303.
^Rossomondo, R. M.; Carlton, W. H.; Trueblood, J. H.; Thomas, R. P. (1 November 1972). "A New Method of Evaluating Lacrimal Drainage". Archives of Ophthalmology. 88 (5): 523–525.
doi:
10.1001/archopht.1972.01000030525010.
PMID4634791.