What are the essential conditions for claiming deduction in the case of permanent physical disability?

Deduction in the case of permanent physical disability (including blindness) [Sec.
80U]
In computing the total income of an individual who is suffering from permanent physical
disability, etc., deduction under section 80U will be allowed if certain conditions are
satisfied.
Essential conditions for claiming deduction under this section :
(1) The deduction is available to a resident individual.
(2) Such individual should be suffering from a permanent disability (physical or mental).
(3) The disability should be to the extent of 40% or more.
(4) In order to claim the deduction, the individual should produce a certificate from a
medical authority.
Quantum of Deduction : Fixed deduction of ` 50,000 is available. A higher
deduction of ` 1,00,000 is allowed in respect of a person with severe disability (i.e.
having any disability of 80% or more).