Electronic Devices With Adjustable Eye Relief

A head-mounted device may include optical assemblies for presenting images to a user. Each optical assembly may have a support with first and second portions that move relative to each other. A motor in each optical assembly may move the second portion of that optical assembly relative to the first portion of that optical assembly. The optical assemblies may each have guide rods along which the second portion of the optical assembly slides relative to the first portion. A lens in each optical assembly may be used to convey an image from a display in the optical assembly to an eye box for viewing by a user. The lens and display may be mounted to the second portion. Face bumpers may be mounted to the first portion. To adjust eye relief, the motor of each optical assembly may move the second portion relative to the first portion.