One of the most commonly asked questions in an eye exam comes right after the refraction, or glasses prescription check: “What is my vision?”

Almost invariably, people know the term “20/20”. In fact, it’s a measure of pride for many people. “My doctor says I have 20/20 vision.” Or, on the other side of that same coin, having vision that is less than 20/20, say 20/400, can be a cause of great concern and anxiety. In this discussion I will describe what these terms actually mean.

To lay...

Here are 11 bad contact lens habits we eye doctors often see--

#1 Sleeping in your contacts.

This is the No. 1 risk factor for corneal ulcers, which can lead to severe vision loss and the need for a corneal transplant. Your cornea needs oxygen from the atmosphere because it has no blood vessels. The cornea is already somewhat deprived of oxygen when you have your eyes closed all night, and adding a contact on top of that stresses the cornea out from lack of oxygen. You don’t need to...