There is a reservation of about 5% seats in IIT for PWD students. To avail the benefits of low vision PWD in JEE, candidates must have 40% of disability as defined by the Right of person with Disability act.

If you have 40% of vision disability, you can avail the benefits in JEE like lower admission fee, little lower cut off marks , lower admission fees etc.

To know more about this, you can visit career 360 website

https://search.app?link=https%3A%2F%2Fengineering.careers360.com%2Farticles%2Fjee-main-reservation-criteria&utm_campaign=aga&utm_source=agsadl2%2Csh%2Fx%2Fgs%2Fm2%2F4

To be eligible for benefits under the Persons with Disabilities (PwD) category in JEE exams, a student with low vision needs to have a disability percentage of 40% or more as certified by a medical board; this means they must be classified as having a "low vision" disability that constitutes at least 40% impairment.

Total of 5 percent reservation given to each category of PWD students.candidates can claim reservation according to the guidelines given by JEE exam.

To understand reservation criteria you can refer link

https://engineering.careers360.com/articles/jee-main-reservation-criteria