Sorry to hear that your chameleon is unable to use its eyes. Are you sure it is blind? or is it just unable to open its eye? Have you sought a second opinion from a vet familiar with chameleons?
If it is in fact blind, I wouldnt assume it is having a bad life. So long is it is getting water when it needs it, food when it needs it, is able to somehow navigate towards and away from heat....
That makes me wonder, does it seem to know where the basking spot is? that would suggest it still senses the light through closed lids.