Very good material that covers optics, refraction, retinoscopy, prism, lenses, refractive errors, estimating refractive errors, refining the data and add powers. It provides a wonderful review of each topic and the speaker builds on top of the previous topic explaining how one works with the other. She gives great examples as needed for each category. I gained a better understanding with some of these areas plus the lecture gave me an overall review that I needed.