As shown by the declension table for the noun version of слепой here: https://en.m.wiktionary.org/wiki/слепой this word apparently is a noun (blind person) but declines like an adjective (prepositional case is слепом and not слепое* as I would expect under the rules I've seen, yet this is not marked as irregular on Wiktionary). Why? Is this a special case where an adjective can act as a noun but stays declining as an adjective?
There are some adjectives that have become nouns as a result of dropping the nominal part of the noun phrase. These adjectives have the semantic meaning of the noun phrase and retain the gender of the dropped noun, but keep their adjectival declension.
Русский,больной, ученый,мороженое,рабочий, насекомое, животное, шампанское.