there are some solutions for it.
get a certificate from the doc which says u r allergic to sun rays. apply to ministry of interior for tints supported by the certificate. ministry will issue the permit stating ur name, father name, address, car make, model, number etc authorizing you to use the tints. this permit is valid for 6 months and can be reissued.
apply to home department/ministry of interior with a copy fir if you have security threats.
for the above solutions, you need to have the right contacts and even the federal capital police does not stop such vehicles.
a source of a friend has imported some setup which tints the windows without using paper. i have seen a car whose windows were tinted using that technology and it looks as if the car originally came with those tints. tints are see through. i would say they are 25 or 50% tints. perfect match. he is not doing it for commercial purposes yet. will ask if anyone frm islamabad is interested.