Optical Coherence Tomography (OCT) is a revolutionising imaging technique of the retina, and can be considered an optical analogue of ultrasonography. It is a non-invasive, fast diagnostic technique. Pauline Kok demonstrates that optical illusions also occur in OCT images. The image quality and interpretation of OCT therefore needs critical evaluation. Her aim is to investigate misinterpretation of OCT scans and measurements due to loss of image quality. Furthermore, the clinical interpretation of OCT retinal (layer) thickness measurements is demonstrated in two ophthalmological diseases.