Even though I wear Bi-focal Custom Subscription sunglasses, hark ye to this - Although dark, the upper part (above the spilt) is additionally silvered for greater light reduction, the lower part is not.  Why, you might ask?  Because sometimes I want to also read a chart and the deep light reduction of a silvered area unduly inhibits one's ability to read charts.  Note That I agree with Speedy Larry that polarized lens will make any LCD display unreadable.