In 2009, McConnell began working with William Bradshaw Amos and built a new lens, Mesolens, that can allow 3D imaging with a depth resolution of a few microns for objects up to 6 mm wide and 3 mm thick. The Mesolens is a giant optical microscope objective supported by the Medical Research Council (MRC). It can be used to image large biomedical specimens, including embryos, tumours and areas in brain, as well as scanning large areas of samples in a short amount of time. The lens has 260 megapixal effective camera and a magic ratio of 8:1, which can even resolve individual bacteria. As the photometric volume can sample such a large area with sub-cellular detail, the Mesolens may allow for the imaging of rare events. Mesolens became a University spin-off, but McConnell decided to stay in academia to explore the physics of biomedical processes. The Mesolens generates such large amounts of data that McConnell became interested in computational biology. The Mesolens was selected by Physics World as one of the top achievements of 2016. She discussed the Mesolens on the podcast Not Exactly Rocket Science.