It is used to disposition product as the acceptance criteria is a visual attribute noted/or not noted at 10 x.
The answer is yes
Whatever your "visual attribute" is that you are verifying through the microscope needs a device that if fit for use and compliant with industry standards. Operator training goes hand in hand but operator's eyesight health (is unique & different) on top of using an optical instrument that is not properly maintained will exponentionally increase variability & inconsistency in your acceptance criteria procedure.
The instrument is used to make a decision of pass vs. fail therefore it should be reliable & reproducible. If equipment is not maintained regularly & consistently, this is a big gap in your quality system & someone will easily figure it out & find it. I look at critical steps in a process, then I look at how are these steps controlled & look deeper into those steps and go even deeper until there is a clear logical description & proof that it is followed every single time during production. If I don't see evidence of it, then it is a non-conformance & I flag it.
Basic preventive maintenance & calibration services can be scheduled from an external vendor annually, you get your paper work and then your are set.
The decision is good for your quality system and the quality of your product but a business decision as well.