I had laser eye surgery a decade ago, but in recent years my eyesight has become significantly myopic. I consulted an ophthalmologist to see if this was eye strain because I work at computers a lot, or part of a natural degradation of the eye over time, or both. My ophthalmologist seems to believe that in my case I'm youngish enough that the natural degradation with age is minimal, and that it's mostly eye strain that is my problem. She believes I can get my eyesight back to roughly 90% of my post-surgery sight ability, if I can reduce eye strain. She gave me some eye drops to help with dryness, and recommended various ways to for me to help my eyes recuperate.

I decided to look into eye strain to learn more about what conditions cause it and what can alleviate it. What I learned is that the lens of the eye needs to be flatter to accommodate focusing on far objects, and rounded to focus on near objects. The way the lens becomes flat is by using spring-like connective tissue called choroids that pull it taught. Attached to these choroids are muscles called ciliary muscles that stretch the choroids out when they contract. This action causes the choroids to stop pulling on the lens, and the lens will retract into a more rounded shape. So, when the ciliary muscles are relaxed, you can see far. When the ciliary muscles are contracted, you can see close up. This diagram from the York University website was the clearest explanation I have come across:

ciliary muscles and choroids

Thus, the reason for my current inability to focus on far objects is that so much focusing on close objects, mainly computer monitors, is straining my eyes. In order to regain the ability to focus on far objects, I need to reduce strain and allow the muscles to relax. If they relax, the choroids can pull the eye to the flatter shape needed to see far.

However, I can't reconcile that model with how I understand the mechanics of the other muscles in my body. If I go to the gym and run or lift weights, or in any way expose my muscles to work, they respond by getting stronger without sacrificing the ability to stop contracting. The muscles in my body don't lose the ability to relax, no matter how much I train them. I have never heard of anyone who worked out too hard or too long such that their bicep would remain in a permanent state of contraction.

In fact, in my experience, after a hard workout, it's impossible to prevent my muscles from relaxing and resisting doing more work. When I do a bicep curl at the gym, and I do it to the point that I can't lift the weight anymore, my muscle gives up and I drop the weight. Similarly, if I've spent a long time looking at close up objects, shouldn't my ciliary muscles give up, allowing the choroids to take over, making clear far vision the unavoidable outcome?

The idea that my ciliary muscles need to relax in order to see far also seems to contradict my personal anecdotal experience. Sometimes I am able to see far away, but I can't hold it for more than a few seconds. If I try to maintain focus on far objects for too long, I get an uncomfortable feeling in my eyes that is hard to describe, but it's a form of pain that forces me to give up. My vision goes blurry, and I can only see close objects again. If my bicep worked the same way, it would be as if it hurt to let my arm hang straight down with a weight, and the only way to alleviate it would be to raise the weight, which makes no sense. I feel like the effort is in seeing far, and that when I'm tired, I can only see close up.

It's not that the case that I think that all medical research on the eye has it backwards, it must be that there is some aspect of this that I am not seeing (pun intended).

How can it be that the ciliary muscles, unlike other muscles, lose their ability to relax?

Why is it that my ciliary muscles don't become exhausted and allow the choroids to take over by default?

  • $\begingroup$ Regarding focusing on far away objects - perhaps that is unrelated to the distance? I imagine you would "stare" at the objects with intense concentration, rather than gazing casually, and would probably blink less and move your gaze direction less, fatiguing the retina. $\endgroup$
    – Superbest
    Apr 21, 2014 at 20:49
  • $\begingroup$ To relax the eye muscles and prevent eyestrain, you can follow the 20-20-20 rule: every 20 minutes look at something at least 20 feet away for at least 20 seconds. That should work for problems that aren't pathological at least but I'm not an expert so take the advice with a grain of salt (the rule is a sound one but the later half of my answer is just my opinion). $\endgroup$
    – user13129
    Jan 21, 2015 at 6:22

5 Answers 5


First of all, I should correct some points that were misunderstood. Don't change the question because this will lead to confusion.

"The way the lens becomes flat is by using spring-like connective tissue called choroids that pull it taught."

In classic ophthalmology you don't need to think about choroid in direct relation to accommodation: choroid is a sponge-like layer between the sclera and retina and in general it is consisted of blood vessels. The anterior part of the choroid continues anteriorly to became a ciliary body which in turn contains ciliary muscle - one circular muscle per eye. From the ciliary body/muscle spread zonules (zonule fibers) and they are fixed on the lens equator.

Physiology: contraction of ciliary muscle causes zonules to became loosen and "free" the lens to became more convex and move the focus anteriorly (not choroid contracts itself). If the ciliary muscle relaxes then zonules are tighten up and the lens consequently becomes more flat (less convex) moving the focus posteriorly. In other words you can say it in the terms of depth of focus - convex lens gives less depth, less convex gives more depth of focus.

Thus, the classical choroid layer does not perform any action (look at your choroid related link - there are almost nothing about accommodation).

"Permanent state of contraction" can be physiological (=normal) as well as abnormal one, and it is very common in some conditions (muscles spasms). One example is priapism, where corporal smooth muscle contraction causes permanent and dangerous penile erection which can be medical emergency (priapism is by far more complex, so take the explanation like a metaphor).

If we refer to "accommodation spasm" there is analogy to "muscle spasm" (and partially to priapism), but I should state we believe that spasm of ciliary muscle exists - since we don't see it directly. Probably (and take this sentence as speculation, since I cannot give you reference right now) the causes of this is not a muscle spasm itself, but the state of zonular fibers which cannot come back to their base state. I like the example with iron rod - if you will contract it fast and many times, at some point it can be "loosen" as well as fractured (and probably it does happens to zonules too). Probably (I say "probably" to underline the point we do not exactly know this), the "accommodation spasm" is partially misname and in future the investigations will clarify that.

Probably, you will learn some interesting facts from definition of "pseudoexfoliation" syndrome, but I do not explain it here because it is not related directly to the question. From wiki "has been known to cause a weakening of structures within the eye which help hold the eye's lens in place, called lens zonules"

Another example for analogy for continued "spasm" is the situation when one should care something heavy for a long distance without releasing the grasp - finally one can get not only spastic contraction but also severe ischemic damage to the fingers.

Considering your case, you should know about pathological (degenerative) myopia where the eye expands posteriorly and consequently the focus is before the retina which should be corrected by minus lenses. It is well known fact that myopic eyes have longer axial length then normal eyes. Probably, it is your case.

So, as you can see, the answer to your question is not a clear cut, but assumption. The ciliary muscle does can relax, but probably the problem is more complex then only ciliary muscle related issue.

PS The image you reposted is a little bitconfusing one and is not exact. This one is classical and gives better understanding of the anatomy -

enter image description here


I'm not a eye doctor but I do workout. I would like to say something about your metaphor or comparison from the ciliary muscle to the body muscles.

Let's look at a workout. In a workout, you strain the muscle then relax the muscle repeatedly until you exhaust the muscle. Another part of the exercise is stretching. If you don't stretch, you will lose full range of motion. For instance, if I were to do a regiment of bicep curls for the first time, and I slept that night with my arm cocked, it would be a painful effort to straighten it the next day. If I don't stretch it my arm would stay in that position having limited motion. The muscle is relaxed but it's range has changed. Another example would be, when I was a teen, I did karate and could do the splits. Now-a-days I can not do the splits no matter how much my muscles are relaxed.

Looking at the computer all day isn't comparable to working out a muscle because you don't contract and relax repeatedly. You only contract.

Now let's look at the body muscles in a more relevant metaphor - Tension. Tension is an involuntary reaction. Because you hold the muscle in a contraction state for such a long time, it tends to want to stay contracted without you making the effort. A lot of people hold tension in their neck and shoulders and no matter how much pain it causes them, they can't relax it voluntarily.

Muscles have a mind of there own (muscle memory). To assume you have complete control over them is wishful thinking. I assume that the ciliary muscle is no different.

  • $\begingroup$ Can you please add some references to your answer? $\endgroup$
    – Chris
    Jun 28, 2016 at 20:53

There are a few more things that need to be considered to get a better understanding of the physiology.

The ciliary muscles are not skeletal muscles (voluntary muscles that you can control) but smooth muscles (involuntary muscles which are under the control of the autonomous nervous system, which is self regulated by the parts of brain not under the conscious control). This has several deep implications.

  1. Smooth muscles do not hypertrophy - grow and become thick like skeletal muscles - They are more or less constant and their growth/strengthening is more related to hormones than regular contraction/relaxation exercises

  2. Smooth muscles are supplied by autonomic nervous system - Parasympathetic system is the main supply. Recently evidence for sympathetic innervation of ciliary muscles has been found.

Generally, there is a balance between the sympathetic and parasympathetic, the balance being driven by the need brain perceives. An imbalance in these systems can cause accommodation problems

  1. This point is speculation based on proved biological laws: Law of tension-stress: This states that if under constant tension, the biological systems grow.

Gradual traction on living tissues creates stress that can stimulate and maintain the regeneration and growth of certain tissues. Slow, steady tension of tissue causes them to become metabolically activated, resulting in an increase in their proliferative and biosynthetic functions. These processes are dependent upon two main factors:

  1. The quantity and quality of blood supply to the tissue being mechanically stressed and
  2. The stimulating effects of tensile forces acting along the lines of muscular contractions because collagen fibers are generally aligned parallel to the vector of tension-stress. source:http://jontristermd.com/for-physicians/the-tension-stress-effect-on-the-genesis-and-growth-of-tissue-2

This may cause changes in the choroid that may reduce the tension on the zonules causing a semi-permanent/permanent myopia.

  • $\begingroup$ Thank you for responding. I think there's some interesting and useful information here in your answer. However, you've used a lot of deeply technical terminology that makes it very hard to follow and understand. If you could rephrase your answer with a non expert audience in mind, I think it would be a lot more informative and helpful. $\endgroup$
    – Questioner
    Jun 30, 2016 at 5:03

After reading various theories of how the ciliary muscle body works, I came across a convincing new theory by Dr Goldberg, one of reciprocal action. In other words, the lens is only under posterior (rear-inner side) tension when focusing on near objects, but anterior (front-outer side) tension when focusing on distant objects. In both cases the lens is under a form of zonular tension. The ciliary muscle moves forward (near focus) and backward (distant focus), actuating the zonular strings and circular apparatus accordingly. As I have witnessed how I sometimes have to force myself to focus in the distance, I am inclined to believe that relaxation of the ciliary body only leads to a medium focus, and while contraction, either forward and backward, for near and distant focussing respectively. In other words, the ciliary body would also contract slightly for a distant focus, but this contraction would be in opposite direction. There's a video illustrating Dr Goldberg's theory: https://www.youtube.com/watch?v=1yIpyitm6eE I must add that there are theories saying that the zonular fibre gets stretched (permanently longer) when using too much near-vision, so that when ciliary muscle body relaxes, the lens is not held taut enough, causing it to be always convex (nearsighted).


The ciliary muscle is made of smooth muscle rather than skeletal muscle. These two types of muscles have different mechanisms for contraction and relaxation. Skeletal muscle is relaxed unless it is stimulated by a nerve. Smooth muscle is able to lock itself into a contracted state through a chemical reaction (phosphorylation). It then does the reverse chemical reaction (dephosphorylation) to relax. This is important because smooth muscles do things like keep the urine in your bladder (urinary sphincter), and you don't want that muscle getting tired and giving up.

  • 1
    $\begingroup$ Can you add references or other credible sources to allow others to background read on your answer? $\endgroup$
    – AliceD
    Jul 21, 2017 at 3:59

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