Vision impaired students should obviously be given appropriate tools to overcome their disabilities. iI think the posts below have done a good job addressing this.

If a student struggles with reading, due to either a learning disability or a lack of instruction in reading, I think it is important for a teacher to make sure he or she is getting adequate instruction in reading. If the science teacher cannot provide the help needed, many schools offer reading specialists and other programs for struggling students. I agree with other posters that school should prepare a student for a future career, and leaving reading based activities out of the science curriculum is doing the child a disservice.

Within a science classroom I think teachers should provide audio and video aids for students. For example, a quick google search turns up many videos illustrating many topics. An animation of the process of transcription and translation could help to clarify a concept that is difficult for students to comprehend from text alone. Embedding such animations in class notes or posting them to a class website will help all students, regardless o their reading ability.

Evaluating the learning of these students is a challenge. Traditional tests may be hard for students, so they must be given adequate time and encouraged to ask for clarification of questions if they do not understand. students may be allowed to answer essay questions with speech recognition technology typing for them, or evaluated using projects or portfolios instead of tests.

I think it is important to include practice in reading during instruction, but it is unfair to the student if their ability to communicate their understanding of the subject matter is hampered by a disability. They must be evaluated in a way that measures their gains in knowledge of science, not their ability to transmit it on paper.