Abstract
Purpose :
Ophthalmic surgeries currently rely on highly variable approximations of injection volumes for drug delivery and gene therapy. Here, we demonstrate the need to estimate retinal feature dimensions across different radial distortions due to varying axial eye lengths. We establish a quantitative method for volumetric estimation of subretinal injections using an intraocular reference with known dimensions.
Methods :
Eye models were designed with 2 x 2 mm columns at 19, 23, 25, and 27 mm axial eye lengths to quantify distortion (Fig 1(a)). Similar models with spherical wells were used to simulate subretinal injections across all eye models. A solidifying agar-TiO2 solution was delivered into the wells, weighed to calculate actual injection volumes, and compared to measured injection volumes from segmented iOCT volumes converted to μm using internal reference dimensions of a cannula.
Results :
iOCT imaging was performed on square eye models and injection models over the same fast- and slow-axis scan ranges. Comparison plots (Fig. 1(b)) show an increase in distortion away from the center of field of view across all models and indicate that distortion increases for smaller eyes compared with larger. Pixel-to-μm scaling parameters were calculated from the intraocular reference cannula (Fig. 2 (a)-(d)) and manually segmented injected volumes (Fig. 2 (e)), demonstrating minimal difference in measurement accuracy and robustness across eye models (Fig. 2 (f)).
Conclusions :
We demonstrated the necessity and methods for quantification of retinal feature dimensions and subretinal injections volumes. The examination of differing eye length models showed optical distortion with known feature dimensions. Future integration of the volume injection quantification method with refraction correction methods and expanded injection studies will enable more precise measurement of intraocular volumes.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.