It is about time someone protests against the praise, honor, and glory given Helmholtz, on his theory of accommodation of the human eye.
As Tscherning violently disagreed with the Helmholtz theory then, I violently disagree with it now. I challenge all who believe the Helmholtz theory of accommodation to give some thought as to whether or not it is even reasonable to believe.
It is not that another theory of accommodation would change eye work as it is being done today, but it could lead to a new understanding of refractive and muscular eye troubles, and might improve the eye work of today and tomorrow. It did this for me over the last forty years.
The crystalline lens of the human eye has little or no elasticity in the first place. Therefore, it could not be the media of accommodation in the second place. Certainly it does not have enough elasticity to focus the human eye, instantaneously, as fast as I can accommodate my own eyes from far to near and near to far. Yet we know that the human eye does have the ability to accommodate instantaneously, for any and all distances.
Then the question arises - if the crystalline lens is not the media of accommodation, what is it there for, and what is the media of accommodation???
The crystalline lens is the core of the eyeball, suspended taut in place in its capsule by the suspensory ligaments, which in turn are connected to the circular ciliary muscles of accommodation. Instead of the crystalline lens becoming more or less convex, as per Helmholtz, under accommodation, it becomes held more or less taut in place, under accommodation.
Under the Helmholtz theory, the crystalline lens would be held less taut in place, and of its own weight it would sag or tip, instead of becoming more or less convex. Its curved surfaces, having a power of 16 to 19 diopters, are more or less neutralized by the curvature of the humors, making the power of the crystalline nil and useless as a refracting media. As a refracting media, eyes could do without the crystalline lens, if internal tone and pressure were not lost in its removal. Suspended taut in its place, it serves as a solid to steady the action of the circular ciliary muscle, and to help keep the eyeball round.
In the act of accommodation, as I see it, the circular ciliary muscle acts in "shoelace" fashion, contracting in itself, drawing the crystalline lens taut and at the same time, making the cornea more or less convex, thereby making the cornea the media of accommodation, instead of the crystalline lens. It has to be that way; it cannot be any other way. At least that way is more believable than the old Helmholtz theory of accommodation. But there is more to say about the cornea, and its power and action under accommodation.
The cornea has more than enough power to do all the focusing for a normal human eye. It is so powerful that it bends all rays, incident on the cornea, directly through even a pinpoint pupil, straight on through the aqueous humor, the crystalline lens and the vitreous humor to the retina. It must be remembered and kept in mind that the point of reversal takes place in the pupil.
Considering a pinpoint pupil, the anterior surface area of the crystalline lens is so small and neutralized by the aqueous humor, that it could have little or nothing to do with refraction. That alone cuts the power of the crystalline lens in half. Then also, the incident and emergent rays pass through the curvatures of the crystalline lens at an almost perfect right angle to its curvatures, on their way to the retina, without being refracted by the crystalline lens, and just as if the crystalline lens was not there.
In the act of accommodation, the cornea becomes more or less convex by the action of the ciliary muscle. The act is so minute that it is not detectable, even with the ophthalmometer. It should be realized that the eye being examined, while looking into the aperture of the ophthalmometer, is under accommodation for the distance it is looking. This gives the corneal curvature under accommodation at that distance. If it were possible to take the corneal curvature with the ophthalmometer while the eye was looking at infinity, it might show less corneal curvature, depending on the type of eye being examined. While there may not be very much difference, this could prove that the cornea is the media of accommodation. I can accommodate either one of my eyes at will. My vision blurs, and I can actually feel the action of the ciliary muscle making the cornea more convex. I can accommodate so strenuously that the object I look at shakes, meaning that my eyeball quivers, but only in the horizontal, as in nystagmus. If I force my accommodation with both eyes together, my vision blurs up to a certain point; then my eyes turn inward, and I see blurred and double. If I then ease up a little in my over-accommodating at will, I still see blurred, but single. If I ease up all the way, I see clear and single.
In my over-accommodating at will, with one eye or both, I am actually making my eyes nearsighted. This means that with my naked eyes, I would see blurred. If I placed a minus lens before my eyes, I would see clear. Doing this under the Helmholtz theory of accommodation, I would be forcing my crystalline lens to bulge into becoming more convex by its own supposed elasticity. If I believed in the old Helmholtz theory of accommodation, I would not dare do that with my own eyes. Not believing in it, and believing in the cornea as the media of accommodation, I do not fear doing it, and overdoing it, if I please, as a matter of experimenting with my own eyes. Since the crystalline lens has little or no elasticity, some other media has to have a lot of elasticity to perform the instantaneous act of accommodating. That other media can only be the cornea. No other media could have such flexibility and elasticity.
Under the old Helmholtz theory, a farsighted eye would mean a lack of convexity of the crystalline lens, and a nearsighted eye would mean an over-convexity of the crystalline lens. This is not even reasonable to believe, but we know it has to be something. If the cornea was the media of accommodation, a farsighted eye would lack convexity of the cornea, and a nearsighted eye would mean an over-convexity of the cornea. That is more reasonable to believe. On close observation of the corneas, one will find that farsighted eyes have a shallow cornea and anterior chamber, while nearsighted eyes have an over-convex cornea and more anterior chamber, with usually large pupils, a glassy and starry-eyed look, and a bulgy eyed appearance.
Under the Helmholtz theory, presbyopia is supposed to be the physiological hardening of the crystalline lens. Since the crystalline lens has little or no elasticity, this theory of presbyopia also is not even reasonably believable. With the cornea being the media of accommodation, presbyopia has to be the loss of power or action of the ciliary muscles, or loss of flexibility of the cornea, or both. It seems that it has to be a loss of power of the ciliary muscles. It is not reasonable to believe that the cornea could have such a fault, or have anything to do with it.
Going beyond what is or is not the theory of accommodation, the crystalline lens and ciliary muscles have another duty to perform. They not only serve to help keep the eyeball round, but all extrinsic muscles oppose each other through it. Without them, the extrinsic muscles could pull the eyeball out of round. The crystalline lens and ciliary muscles could perform such duty better with the cornea being the theory and media of accommodation, than with the old Helmholtz theory.
Any theory of accommodation would be hard to describe. If one would imagine the crystalline lens as a solid suspended in place, the ciliary muscles as a muscular ring, and the extrinsic muscles attached to it under tension, one would have a better picture of the cornea as being the media of accommodation.
One has to have a strong imagination to picture the act of accommodation under the old Helmholtz theory. One may not be able to catch the cornea becoming more or less convex in the act of accommodation, but that does not mean that anyone has ever caught the crystalline lens becoming more or less convex, in the same act. What proof is advanced, in an attempt to prove the crystalline lens as the media of accommodation, could be credited to the act of the cornea. In fact, as stated previously, the act of accommodation in the human eyes is so minute as to be beyond detection, whether the media be the cornea or the crystalline lens. However, in either case it takes the action of the ciliary muscles, which in normal eyes should be as active as the hairspring of a watch, to activate accommodation. Whatever the media of accommodation, it has to be fast and instantaneous. In any case, as I see it, it can only be the cornea.
With the theory of the cornea being the media of accommodation in mind, I was able to go even farther into the cause and condition of all refractive and muscular eye troubles, especially in cases of children and young people, and do something about it. This I could not have done under the old Helmholtz theory. If others would do as I did and do some thinking, they might run into the same thing. If they did, they would find it as revolutionary as I did.
Right now I only wish to establish a change in the theory of accommodation, from that of Helmholtz to what it should have been all these years. Once and for all, I would like to see the old Helmholtz theory of accommodation thrown overboard, and establish the cornea as the media of accommodation of the human eye. In doing that I would discredit Helmholtz, as he should have been discredited years ago for holding back advancement in thinking, in eyework, for all these years.