Retinoscopy

Device is use to check power of the eye

When test your eye power. Are you looking for best machine to test your eye?
These are my answer:
There are two ways to test your power it is either objectively, it mean without your response of seeing we test your eye or subjectively which you need to response to everything you see.
Objectively, your power can be measured using a device called autorefractor and retinoscopy.
What are the difference?
Autorefractor is usually done fully automated by machine which as retinoscopy need a person to look into your eye.
Autorefractor is good in the sense that it is a quick way to measure the power of the eye. But most of the time, the accuracy and the repeatibility of the result is questionable.
Compare to retinoscopy, the examiner can see the state of the person eye whether the person is relaxing or not. Therefore it can easily direct the person to relax. In this case, the result is more accurate and reliable. Unfortunately retinoscopy need a lot of experienced from person to handle it. Because the examiner is viewing the light reflecting from the back of your eye. The light can scatter in every direction esp those who with cataract or cornea problem or even tears problem which can be seen thru this scope. Whereas an autorefractor can only give error result.
Therefore, most optometrist will prefer to use retinoscopy compare autorefractor. Because this is the way the examiner can tell how the light get into your eye.