VECAT 2004Low.

Methods	Vitamin E, Cataract and Age‐Related Maculopathy Trial (VECAT). Randomised, double blind, placebo‐controlled trial with parallel group design (two intervention groups).
Participants	Country: Australia. Number of participants randomised: 1193, 44% men and 56% women, aged 55 to 80, mean age 65.7 years. Inclusion criteria: good general health, early or no cataract. Exclusion criteria: prior cataract surgery, advanced cataract in both eyes, glaucoma, known sensitivity to vitamin E, and long‐term treatment with steroids or anticoagulants.
Interventions	Participants were randomly assigned to receive: group 1: vitamin E (natural vitamin E in soybean oil) 500 IU (n = 595). group 2: placebo (n = 598); for four years.
Outcomes	The primary outcome measures were: major age‐related types of cataract: nuclear, cortical cuneiform, and posterior subcapsular.
Notes	Compliance with the trial medication was determined by counting capsules in the returned medication bottles and by measurement of plasma vitamin E levels in a random sample of participants. Overall, 77% of the actively treated group and 79% of those participants randomised to placebo were estimated to have consumed 80% or more of their capsules. After 4 years of follow‐up, 74% of the vitamin E group and 76% of the placebo group remained on their assigned medication and participated in the annual reviews. Among the remaining 25% of the participants, 12% in each group ceased taking the assigned medication but continued participating to have their eye examined. Overall, 60 participants from the placebo group and 58 participants from the vitamin group withdrew from the trial. The trial was funded by Smith and Nphew, Australia, Henkel, Australia.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Sequence generation was achieved using computer random number generation.
Allocation concealment (selection bias)	Low risk	Allocation was controlled by a central and independent randomisation unit, so that intervention allocations could not have been foreseen in advance of, or during, enrolment.
Blinding (performance bias and detection bias) All outcomes	Low risk	The trial was described as blinded, the parties that were blinded, and the method of blinding was described, so that knowledge of allocation was adequately prevented during the trial.
Incomplete outcome data (attrition bias) All outcomes	Low risk	The numbers and reasons for dropouts and withdrawals in all intervention groups were described.
Selective reporting (reporting bias)	Low risk	Pre‐defined, or clinically relevant and reasonably expected outcomes are reported on.
Other bias	Low risk	The trial appears to be free of other components that could put it at risk of bias.