I must draw a tangent from the subject of the eye, if only for a moment, to describe a relevant scientific phenomenon which involves the adaptatory
mechanisms of human and most animal muscle. Imagine holding a twenty pound dumbbell in a curl. At first it seems alright, your arm is bent and you're
feeding energy to your bicep in order to keep it contracted. As you start to run an oxygen deficit, your body starts producing energy anaerobically,
through the fermentation of lactic acid. This acid begins to burn your muscle, and you begin to feel pain. But let's say you don't care, and you're
going to keep the dumbbell. Let's say through sheer force of will, you kept it up for three or four hours, and once bored, you try to let it
down...but you can't. You attempt to extend your arm downwards, but are met with huge pain and actual physical resistance. You are forced to let the
weight slide off your fingertips and crash into the ground. You see your muscle, realizing you weren't going to let it relax chose to do the only
thing it could to prevent itself from forcefully relaxing and having the weight fall onto your toes; it shortened itself...it changed the structure of
it's fibres to become shorter, so that the position it was in; contracted, became its new base, requiring very little energy to maintain. For the man
with the dumbbell, hours will pass before his muscle will start to lengthen again due to simple effort and the disappearance of the weight, and within
a day or two, he'll be back to normal. Unfortunately, the same cannot be said for all muscles, as we'll soon see.
Back to they eye! Before we get straight to the point, I must first explain when you are focussing and when you are not. Case 1: A man looking into
the distance, dreaming about where he could be, what he could do, and why he hasn't gone there and done these things yet. Is he focussing; that is,
are his cillary muscles contracting? No, they are not. For a person with 20/20 vision, optical infinity; that is, the distance at which the cillary
muscles are completely relaxed, is 20 feet, and presuming “the distance” is further than 20 feet, his cillary muscles are completely relaxed.
Case 2: A man is watching a television, ten feet away. In this case, he is focussing...his cillary muscles are in a contracted state. Let's give this
level of contraction a value of 100.
Case 3: A man is reading a book, 8 inches away, In this case, his cillary muscles are much more contracted than when he is watching a television set
10 feet away. His cillary contraction level is over 100.
Case 4: A man who has 20/40 vision is watching a television 10 feet away. He is NOT focussing. His cillary muscles are NOT contracted. His optical
infinity is 10 feet away, since he has half the visual acuity of the man with 20/20 vision. Remember this
What does this mean exactly. Since the cillary muscle is attached at two points, the eyeball structural components, and the lens, it is pulling on
both with equal force when it chooses to contract. The harder it is contracted, the more force is imparted upon these two sides. Now taking the story
of the man with the dumbbell into account, imagine a person reading a book for 2 or 3 hours, or using a laptop, or what have you. What is the state of
the cillary muscle after this? In order to adapt to the constant pressure, it has adopted a new, squished shape. This is why even a normal sighted
person will have their vision blurry after doing near work for a significant period of time. Even when they stop doing whatever it was they were
doing, the cillary muscle is still contracted, and the eye is focussing on far away stuff as if it is focussing on closer stuff, leading to a blur,
since the whole mechanism with which the eye focusses lightwaves perfectly onto the retina is thrown off by this temporary condition of the cillary