Identification of Anomalous Features of Intravitreal Injections Using Micro-Computed Tomography

Purpose: To identify anomalous features that impact drug delivery in the eye as a result of intravitreal injections using micro-computed tomography imaging. Methods: Three-dimensional micro-computed tomography images were acquired following an intravitreal injection of 0.03 mL of contrast agent into ex vivo porcine eyes (n = 24). A baseline scan was acquired prior to injection to detect any abnormalities in the eyes. Acquisition continued at various time intervals up to 230 min post-injection. Results: Air bubbles were clearly visible within the vitreous of 21 eyes following injections. There was a total of 36 air bubbles in the 21 eyes and the volume of the air bubbles ranged from 0.01 mu L to 1.50 mu L. It was found the size of the air bubbles decreased over the scanning period. Furthermore, many of the injected boli in the eye specimens did not have the commonly assumed spherical shape; rather, a variety of other shapes resulted. Conclusion: The presence of air bubbles and inconsistent bolus shapes have indicated that intravitreal injections have high variability. It is only through the realization of these anomalous features that the efficacy of intravitreal drug delivery will be improved through a consistent and accurate injection technique.