<prompt> Keratoconus is associated with all except-Downs syndromeEhlers-Danlos syndromeMarfans syndromeUshers syndrome  <response>: Keratoconus may be associated with : Ocular conditions e.g. ectopia lentis, congenital cataract, aniridia, retinitis pigmentosa, and vernal keratoconjunctivitis VKC.Systemic conditions e.g., Marfans sysndrome, atopy, Downs syndrome, Ehlers-Danlos syndrome, osteogenesis imperfecta and mitral valve prolapse. Reference:Comprehensive ophthalmology,AK Khurana,4th edition,page no.120 