Reading Glasses
"Reading" glasses differ from traditional prescription glasses in that they're not intended for full-time use, but rather to aid people with vision problems in reading materials that are close to them. They're sold at drug stores and other retail outlets, are inexpensive and may be the choice you're looking for if you can't afford an eye exam or prescription glasses for your visually-impaired child as he learns to read.
Increase Light
In simple terms, the eye functions to capture light and images so that the brain can interpret them. Increasing light also increases the percentage and detail of a certain image the eye can capture. This technique isn't going to solve your child's vision problems completely, but he'll be able to read more easily if lighting is optimal.
Braille Supplements
If your child's vision is extremely poor, consider speaking with her teacher and enrolling her in resource classes where she can supplement regular reading classes with braille instruction. Although braille is usually the choice of blind individuals, using braille to reinforce your child's reading ability before you're able to fully address vision issues can ensure she acquires reading skills regardless.
Print Size
For documents printed from an electronic form or short ones that aren't difficult to re-type, consider enlarging the font or print size to make it easier to see. Alternatively, you can use a copy machine to enlarge the copy, although the latter technique may be limited unless you have a range of paper sizes.