As we've launched visor - magnifier app for people with low vision on the iOS platform in late december 2014, we didn't know, if our three button magnifier concept would succeed in the App Store. Of course we've tested our concept with vision impaired people, but how to attract their attention in an AppStore, that has millions of apps and thousands of magnifier apps!?
We didn't have any marketing budget at all — and it still is a no budget marketing. But we have a growing community of people recommending visor and using it every day.
Here are some stats, that you might find interesting.