A base support arm is provided for an ophthalmic instrument with a moveable optics head. The base support arm is configured so that the support arm must be deployed to stabilise the instrument before the instrument head can be moved sideways in a manner that could otherwise destabilise the instrument. In addition, an angled chin-rest assembly pivot axis is provided that moves the chin-rest assembly from a compactly folded shape into a position that is suitable for supporting the patients head. The support arm is linked to the chin-rest assembly pivot by a linkage or other mechanism so that movement of the support arm also unfolds the chin-rest assembly and ensures that the chin-rest assembly cannot be unfolded without deploying the support arm.
