If you're thinking about buying an eye refraction machine, there are a few things you should know first. The type of machine you buy depends on your needs and the type of eye examination you're doing. 

Some basic types of machines include manual and automated machines. Manual machines require a doctor or technician to run the machine, while automated machines do the work for you. There are also computerized machines that use software to perform the examination.

You can also buy an eye refraction test machine online via https://www.ai-optic.com/product.

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The type of eye examination you're doing is also important to consider. For example, if you're buying an automated machine for your regular checkups, you may want to choose a model that has features that allow you to customize your examination. This will help ensure that the exam is accurate and consistent, no matter who is performing it. 

Another thing to keep in mind when buying an eye refraction machine is the price range. You don't need a high-end model to get good results; in fact, some of the lowest-priced models are just as effective as more expensive models. 

However, if you plan on using your machine regularly, it's worth investing in a more expensive model that will last longer and offer better performance.