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>