Depends: The needed light amount will vary with the individual as there are no standards for this. It also depends upon the distance of the light from your eyes and whether or not you need reading eyeglasses. There is no app to measure lumens and devices to do this are expensive. A photography light meter would be a less costly option. Trial and error is the best for this.
Answered 12/10/2017
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7 doctors weighed in across 2 answers
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