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Retina. 2014 Jul;34(7):1473-6. doi: 10.1097/IAE.0000000000000098.

Volume and composition of reflux after intravitreal injection.

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*Scheie Eye Institute, Department of Ophthalmology, Perelman School of Medicine, †Penn HHMI-NIBIB Interface Program in Biomedical Imaging, Department of Bioengineering, and ‡Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania.



To quantify the amount of drug loss from cadaveric human eyes, which are injected via the pars plana with a known volume of dye at variable intraocular pressures.


Eight cadaver eyes were divided into 2 intraocular pressure groups: normal (15 mmHg; 4 eyes) or high (30 mmHg; 4 eyes). Each eye was injected with 50 μL of hematoxylin dye, and the subsequent reflux was immediately collected on a Schirmer's test strip. The test strip was scanned and digitally analyzed to determine the area of saturation and total color intensity present. Using a previously established equation, total volume of reflux and the amount of dye within that reflux were calculated.


The average total volume of refluxed fluid was 1.68 μL (median, 0.62 μL), with a range of 0 μL to 8.05 μL. The average volume of refluxed dye was 0.37 μL (median, 0.08 μL), with a range of 0 μL to 2.15 μL. On average, only 0.74% of the original 50 μL of injected dye was lost (median, 0.15%), with a range from 0% to 4.30%.


Although the presence of subconjunctival bleb formation after intravitreal injection may be a concern to the clinician, data from the present study shows that only a very small amount of the injected therapeutic agent is lost in the reflux.

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