Ever been watching a scary movie and wished you could shield your eyes from what’s on the Big Screen without the shame of actually having to shield your eyes? For some people, not seeing what’s in front of them is a simple case of relaxing the ciliary muscle, but not everyone can blur their vision on command.
The ciliary muscles help your eyes to focus by changing the shape of the lens. When it’s relaxed, it pulls on fibers that cause the lens to flatten and thin out. When they contract, the opposite happens, releasing tension on the lens so it becomes fatter and rounder.
Our focusing power is strongest when the lens is spherical rather than flat because it’s better able to bend and refract light so that it’s focused on the retina, meaning contraction of the ciliary muscle improves the clarity of our vision. When it’s relaxed, things get a bit blurry.
Curiously, some people appear to be able to voluntarily relax the ciliary muscle so that their vision becomes unfocused. It’s a skill Dr Karan Raj describes as “the world’s most useless superpower," but not everyone has it. Excuse us while we enroll in Godolkin University.
And to make it even more useless, it seems doing it too often can get you in trouble.
“Excessive unfocusing can lead to visual strain and fatigue,” says Raj. “Constantly shifting between focused and unfocused states might overstimulate the ciliary muscle and the eye’s focusing mechanism. Repeating this divergent squint too often could disrupt your normal binocular vision, coordination between the eyes, and eye alignment.”
Voluntary relaxation of the ciliary muscle isn’t the only visual phenomenon that’s not shared by everyone. About 76 percent of all non-visually impaired people experience something known as "floaters". These appear as moving structures, like little worms, that sometimes appear in your field of vision if you are staring at something bright and uniform such as the sky, snow, or a white screen.
Their scientific name is Muscae volitantes, or "flying flies" – but they are not insects. As an excellent TED-Ed video explains, they are tiny objects within your eyes. They could be bits of tissue, red blood cells, or protein clumps floating in the vitreous humor. This is the gel-like substance between the lens and the retina that keeps the eye in shape.
It’s a reminder that there are all sorts of subtle ways in which our perceptions of the world around us can vary. And when it comes to interpreting those perceptions? Well, don’t even get us started on aphantasia.