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Sudhir Rachapalle, Subashree Murugan, Prema Padmanabhan, Dr. Pavani Murthy, Uday B Kompella, Sangly P Srinivas; Ocular spot fluorometer equipped with a lock-in amplifier for measurement of aqueous flare. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4216.
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To evaluate a custom-made ocular fluorometer for detection of intensity of light scatter (ILS) from the anterior chamber (A/C) as an objective measure of aqueous flare.
The fluorometer, equipped with a lock-in amplifier and having an axial resolution of 250 mm, was employed in the scatter mode to measure ILS (expressed in mV) from the A/C. Measurements were performed with two illumination slit widths of 0.5 and 0.25 mm. Healthy and pseudophakic eyes, who show Grade 0 of aqueous flare as per the Standardization of Uveitis Nomenclature (SUN), were employed as control subjects. ILS was also recorded in a cohort of patients who had undergone phacoemulsification and showed Grades 1+ or 2+ on postoperative days 1 and 4.
The inter- and intra-observer variabilities in the measurement of ILS were insignificant (inter-observer: p = 0.99 for 0.5 mm and 0.97 for 0.25 mm; intra-observer: p = 0.09 for 0.5 mm and 0.59 for 0.25 mm). In post-cataract patients, ILS was significantly higher on Day 1 (0.24 ± 0.11; n = 94) relative to healthy eyes (0.15 ± 0.03; n = 46). By Day 4, ILS (0.19 ± 0.07; n = 40) decreased significantly and was only marginally different from ILS in quiet pseudophakic eyes (0.17 ± 0.10; n = 42) or healthy eyes. Eyes with higher SUN scores showed proportionately increased ILS with both 0.5 and 0.25 mm (Fig.). The receiver-operator-characteristic analysis indicated no advantage in using the smaller slit width in discriminating ILS at different SUN scores although smaller slit width provided significant increase in axial resolution.
The lock-in based spot fluorometer is reliable for measurement of ILS with high precision and accuracy. The measured ILS correlates linearly with SUN scores and can be used to provide a higher granularity for recording aqueous flare. The instrument can be used in clinical management of uveitis and drug development towards uveitis.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
ILS values Vs Sun scores for different slit widths
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