Very difficult to tell exactly what could be the reason behind this. I n my opinion, as you belong to South Africa where Oncocerciasis ( Also called as River blindness
) is common, you might had bite with black fly. Basically in this disease after the bite Oncocerca volvulus ( Parasite) enters in the subcutaneous space ( Skin) ( The reason you had redness
). It may involve any (from cornea
) part of the eye subsequently ( The reason why your eye might have turned red) and lead to subsequent blindness. It could have been prevenyed if you had would have used drug called Ivermectin
Its a public health problem in your area and there is a separate programme for it ( Oncocerciacis control programme) You will get further details online. I hope this solves your query.
Wish you good health