Wilsher v Essex Area Health Authority [1988] AC 1074 is an English tort law case concerning the "material increase of risk" test for causation.
The defendant hospital, initially acting through an inexperienced junior doctor, negligently administered excessive oxygen during the post-natal care of a premature child who subsequently became blind.
On the "balance of probabilities" test, the hospital would not be liable, since it was more likely that one of the alternate risks had caused the injury.
The Court of Appeal applied the "material increase of risk" test, first espoused in McGhee v National Coal Board.
The House of Lords found that it was impossible to say that the defendant's negligence had caused, or materially contributed, to the injury and the claim was dismissed.