Vertical Center an Image Within a Link (or Div)

How to vertically center an image within a div:

<style>
    .valign-helper{
        display: inline-block;
        height: 90px;
    }
    a img{
        display: inline-block;
        vertical-align: middle;
    }
</style>

<a title="my title" href="#">
    <span class="valign-helper"></span>
    <img src="image-path" />
</a>