For line skipping and visual tracking more generally, try BeeLine Reader. [1] It is used as a speed reading tool by some, but is also used as an assistive technology by people with visual tracking issues, attention issues, and dyslexia. The Chrome extension has a 2-week free trial, and the iOS extension is completely free. It's also now available on textbooks, though may not be available on medical textbooks.
Disclosure: I am the founder (and am happy to send you a free pass to our Chrome extension, if you find it helpful).