Geerling studied medicine at the medical school of the RWTH Aachen University and in England.
From 1997 until 2000 (funded by the DFG and Special Trustees) and in 2003 he worked at Moorfields Eye Hospital and the associated Institute of Ophthalmology, University College London receiving subspecialist training from John KG Dart, J Richard O Collin and Geoffrey E Rose in corneal and oculoplastic surgery.