I have two sons who struggled to learn to read. When the one hadn't learned to read by winter break in first grade, I bought "Hooked on Phonics" and taught him myself. The "learn to read by osmosis" approach in his school just didn't work for him.
Through our quest to address the boys' learning needs, the teacher who worked with them at Jefferson Academy noticed they had tracking problems. This was demonstrated in their difficulty in copying problems from the board. Their eyes didn't follow the line and then go to the next line of text. This was addressed by having them do eye exercises and finding sequential letters in random letters representing "words." One of the eye exercises involved my son laying on his back and me standing above him with a tennis ball suspended on a string. I'd move the ball in a circle and watch his eyes track it. His eyes would jump around rather than making a smooth circle. This meant I'd have to slow the ball until his eyes followed it smoothly. We did this every day for a long time and it, along with everything else we were doing at home and at school, made a difference. Additionally, the eye doctor prescribed reading glasses for my son so his brain wouldn't have to strain as much to read/see text and could instead focus on comprehension.
Years later several charter schools starting purchasing and using a Visograph. The Visograph is a computer with "goggles" attached. I did the examination myself to see what it was like. I read a paragraph, with the goggles on. The computer got data from the movement of my eyes to show how many regressions I had (didn't track to the end of a line before jumping to the next line), how fast I read, and numeorus other data. After reading the paragraph I answered 10 comprehension questions on the computer. After analysis and diagnosis, the Visograph programs offers computer-based therapies. For example, the text on the screen may be in different colors for students who find they can read better with a yellow overlay. Another program only shows one word, or phrase, at a time to teach the student to read every word in the line before going to the next line.
Oftentimes students have a physiological reason for an inability to read. Whether it's their eyes, how they process auditory information, how their brain receives and transmits oral/auditory information or some other reason, this physiological barrier--if not addressed--changes their lives forever.