This is the second biennial interim report for the study titled The Effect of a Monocular Helmet-Mounted Display on Aircrew Health: A Cohort Study of Apache AH Mk 1 Pilots. The principal aim of this occupational health study is to determine if the use of the monocular Integrated Helmet and Display Sighting System (IHADSS) helmet-mounted display (HMD) in the British Army's Apache AH Mk 1 attack helicopter has any long-term ...