We are so accustomed to using optical biometry that sometimes we don’t know exactly what to do when the cataract is so opaque that it blocks our measurements. In the photo above, it is evident that an optical method to measure the axial length simply will not work. We can’t even see the retina and must resort to performing an ultrasound B-scan. Similarly, to measure the axial length, we may need to use the ultrasound A-scan but how can we ensure a high degree of accuracy? And what about cases where there is a dense central PSC cataract but the rest of the lens is less affected? Should we measure just the one affected eye or both? What if the two eyes end up having different measurements? How can we ensure that our technique was correct and that we are not stuck with operator error? Ahhh, so many questions. Luckily, I have so many answers. This video gives you my very best pearls using three of my own cases as examples.