elf's description of the eye brightener says it will "perk up those eyes & diminish the appearance of dark shadows" you can buy this from http://www.eyeslipsface.co.uk/ for £3.00
I did look at youtube videos before i purchased to get a general census and i must say i got a few mixed reviews, but i thought I'd give it a go anyway and I'm glad i did as in my opinion this is a very good product.
I've only used it under my eyes but e.l.f says you can use it anywhere you want to brighten and as a
NO BRIGHTENERWITH BRIGHTENER
As you can see the eye brightener really makes a difference to the dark lines around my eyes (NOTE: i have no other make-up on) and it blends in very well with my own skin tone i applied it with a blending brush in outward strokes from my inner corner to my outer eye.
VERDICT: 8/10 because I don't know if this would suit darker skin tones but for me it's very very good and a repurchase item
(I payed for this item myself)