Evaluation of a portable manual stretching device to simulate accommodation

Purpose To evaluate the performance of a manual lens stretching device using clinical scanners to analyze variations in lens topography and cross sections. Methods The stretching device consists of 6 pulling elements, attached to an external ring, which act like an aperture. The anterior segment of enucleated eyes from six months old pigs were glued to the device, then the cornea and the posterior segment of the eye were removed; finally, the whole setup was placed inside a container, which controls the stretching process. Different clinical scanners (Casia OCT, Orbscan and Pentacam) were used to analyze variations in lens shape. Calibrations were achieved using an artificial lens of known dimensions and refractive index. Results The device allows for a radial increase of 1.8 mm. Lens topography could be analyzed using the Orbscan and the Pentacam. While lens cross sections were obtained using the Casia OCT and the Pentacam. The posterior surface of the lens could not be correctly visualized. With our tests we observed changes in porcine lens diameter, shape, surface topography and dioptric power during stretching. Conclusions This stretching device allows for the analysis of the anterior surface and cross sections of the lens. Its capabilities are comparable to larger static stretchers, but has the advantage of being portable, allowing it to be used with the clinical scanners the center already has destined to patients, making it a cheaper alternative. However, the forces can't be measured.