(n.) Failure to cognize, apprehended, or notice.

albinism astigmatism astigmia bad eyesight blurred vision deafness defect of vision dim-sightedness dogmatism double sight double vision faulty eyesight imperceptiveness impercipience imperfect vision incognizance incomprehension insensibility mindlessness nearsightedness nonrealization nonrecognition nonunderstanding nystagmus partial blindness positiveness purblindness reduced sight shortsightedness tunnel vision unapprehendingness unawareness unconsciousness undiscerningness unmindfulness unperceptiveness unpersuadableness unwittingness