A person who is registered as blind in a register compiled by a local authority under section 29 of the National Assistance Act 1948 (welfare services) or, in Scotland, has been certified as blind and in consequence he is registered as blind in a register maintained by or on behalf of a regional or islands council, but a person who has ceased to be registered as blind on regaining his eyesight shall nevertheless be treated as so registered for a period of 28 weeks following the date on which he ceased to be so registered.