I 've had several students with partial sight. Here are some strategies
that may help. Use bright colored materails with different textures to
make examples and for students works. Mylar, bright colored papers of
different textures, string, twine, yarn, and beads, mosaic materials, and
natural materials are easy to obtain.
For gradation, you could correlate texture and size of materials to
gradations in value. For example, make examples with sand, rice, pea
gravel, and so on to show gradation of color value and texture. The
students could use those same materials to create art that shows changes
in value or gradation.
To teach about 2 point perspective you could make a poster sized
"touchy-feely" example emphasizing textures of a city scape drawing or a
copy of a famous painting. Use heavy string where the lines of the
building and glue lines to go to the vanishing points. The students could
trace the lines with their fingers. Even kids with good vision will be up
there touching your example.
There is an interactive website that teaches the concepts of perspective.
If your visually impaired student has access to a computer with a large
screen she could work with the program. The site is :