Microstructured optical arrays (MOAs) are instruments for focusing x-rays. MOAs use total external reflection at grazing incidence from an array of small channels to bring x-rays to a common focus. This method of focusing means that MOAs exhibit low absorption. MOAs are used in applications which require x-ray focal spots in the order of few micrometers or below, such as radiobiology of individual cells. Current MOA-based focusing optics designs have two consecutive array components in order to reduce comatic aberration.