Previously, researchers thought that, when reading, both eyes focused on the same letter of a word. But a UK team has found this is not always the case. In fact, almost 50% of the time, each of our eyes locks on to different letters simultaneously.

At the BA Festival of Science in York, the researchers also revealed that our brain can fuse two separate images to obtain a clear view of a page. Sophisticated eye-tracking equipment allowed the team to pinpoint which letter a volunteer’s eyes focused on, when reading 14-point font from one metre away.
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The team’s results demonstrated that both eyes lock on to the same letter 53% of the time; for 39% of the time they see different letters with uncrossed eyes; and for 8% of the time the eyes are crossing to focus on different letters. A follow-up experiment with the eye-tracking equipment showed that we only see one clear image when reading because our brain fuses the different images from our eyes together.