Volume and Composition of Reflux After Intravitreal Injection

PURPOSE: 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. METHODS: 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. RESULTS: 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%. CONCLUSION: 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.