COMT Practice Exam 2025 – Complete Resource for Exam Prep

The bearings on which the cross cylinder ride are the parts of the phoropter that can be lubricated for smoother operation. This is crucial because the cross cylinder is a key component used to test and correct for astigmatism during refraction. Lubricating the bearings reduces friction, allowing for a more precise and effortless adjustment of the cross cylinder, which helps in achieving accurate visual assessments.

In contrast, the housing of the device is typically not intended to be lubricated, as it serves primarily as a protective outer shell. Lubricating the dial mechanisms may also interfere with their functionality, as these mechanisms are designed to operate without excess lubrication that could attract dust or debris. Furthermore, the adjustment knobs are generally engineered for a smooth tactile experience without the need for lubrication, ensuring consistent control without the risk of slippage or reduced responsiveness. Thus, the bearings specifically support the movement and functionality of the cross cylinder, making them the focus for lubrication.