Dacryoscintigraphy

Abstract

Dacryoscintigraphy is a grossly underutilized nuclear medicine procedure for assessing the patency of nasolacrimal ducts. It is an alternate noninvasive modality requiring no added expertise when compared with dacryocystography, an invasive radiological counterpart. Dacryocystorhinostomy (DCR) is a surgical procedure in which a patent rhinostomy is made so that a low-pressure lacrimal bypass system is created, thus relieving epiphora, dacryocystitis or mucocele. DCR has been accepted as a highly successful procedure in the management of epiphora from nasolacrimal duct obstruction; however, adverse local effects can reproduce epiphora. This study highlights the utility and simplicity of dacryoscintigraphy in the postoperative setting of DCR, apart from showcasing its high sensitivity and accuracy in localizing the sites of lacrimal drainage obstruction. Fifty-five postoperative patients of DCR were screened. Ten volunteers constituted the control group. One drop (10 μl) of technetium pertechnetate (TcO4) was instilled simultaneously in the outer canthus of both eyes (50-100 μCi). Upright dynamic (8 min) and anterior static images of the eyes (up to 20 min) were acquired on a gamma camera fitted with a high-resolution collimator. Physiological interventions that were used in this study were eye blinking, saline intervention, and lacrimal sac massaging. Out of 40 symptomatic DCR patients, 22 had complete obstruction at the presac level and 18 patients had partial obstruction. Quantitative parameters like tear transit time and lacrimal sac half-life were also calculated. After massage of the lacrimal sac, progression of the tracer was observed in five patients. Premassage and postmassage tear column measurements showed a relative increase of 30.1%. Massage of eight clinically normal ducts showed a relative increase of 2.4% (P=0.06). Statistical analysis using the Fisher test shows very significant concordance between clinical symptoms and dacryoscintigraphy findings in postoperative DCR patients (P<0.0001). The modified McNemar's pair test did not show statistically significant differences between dacryoscintigraphy and the syringing irrigation test. Dacryoscintigraphy is a simple and easy-to-perform investigation providing high sensitivity in epiphora detection in patients after DCR. Interventions play a role in further enhancing the sensitivity of the technique. This study demonstrates the utility of dacryoscintigraphy in detecting subclinical and partial lacrimal duct obstruction with good patient compliance. It provides an easy and effective way of screening families, enabling an early diagnosis. During imaging, a high-resolution collimator is found to be an efficient substitute for the conventional pinhole collimator.