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Ophthalmology, Publication of the section

V.I. Shurkin
(Moscow)

ONCE AGAIN ABOUT THE HUMAN EYE ACCOMODATION

(rus. / eng.)

In the article, based on an analysis of the theory of Helmholtz, addressed a number of contradictions to the laws of natural sciences, in accordance with which an attempt was made to define the role of smooth and cross-striped muscles in normal human eye accommodation.

Keywords: cross-striped (CSM), oculo-motor muscle (ОMM), smooth muscle (SM), cyliar muscles (CM), pupil-convergent reflex (PKR), self-regulating and self-tuning function system (SFS), distinctive physiological property, сontradiction, accommodation, the visual fatigue, spasm of accomodation, residual muscle contractures, residual deformations of the sclera.

In visual act of human involves two types of muscles, each with different physiological properties: cross-striped (CSM), provided by oculo-motor muscle (ОMM) and smooth muscle (SM), provided by Iris and cyliar muscles (CM). The latter, according to the Helmholtz, plays a leading role in accomodation act.

The main distinctive physiological property of the SM is as follows:

1) ability to implement the relatively slow movement. Speed reduction SM of different organs is 2-15 cm/s, and most of all - 15 cm/sec is SM of the pupil. For comparison - speed reduction of various CSM is 3.5 -5.0 m/s, and the fastest - inner direct muscle eye - 7.5 m/sec, which is 30-350 or more times the speed reduction is. Especially slow SM relaxation after their reduction;
2) tone and motor functions of the SM are governed by impulses, coming in at parasympatic (autonomous) nerves, therefore they are not bound by the determined efforts of the human, and therefore did not lend themselves to any training;
3) SM come easy long strong reducing condition - plastic tone, with very low energy costs. Therefore SM practically are little tired;
4) physiologically adequate irritant to reduce SM is their rapid and severe distension.
Consider the basic contradictions theory of Helmholtz laws of natural science.

The first Contradiction. Operational "settings" eye on a clear vision of the diversity-remoted objects, as evidenced in our daily experience is implemented synchronously with the eye movements. If this act has SM, then "settings" eyes would be very slow - 30-350 and more times slower than moving the eye. However, in reality we do not have.

The second Contradiction. In humans, there is no physiological act whereby a muscular organ committed to mechanical work on the level of its relaxation. This contradicts the laws of human physiology, and the law of conservation of energy. The latter reads as follows:

1) If multiple bodyes interacting among themselves (sistem bodyes) can make work, say they have energy;
2) mechanical work is performed when the body moves (moves, deformed etc) under the action of external forces applied to it;
3) when performing the work energy of body changes: potential energy into kinetic, kinetic - into potential.

In the model of cyclo-lenticular accomodation of the Helmholtz are also interacting system between bodyes, each with energy, could carry out mechanical work in relation to each other. However, CM , as one of the components of the system of interacting bodies, while in a relaxed state, cannot possess energy, and therefore unable to complete the mechanical work - distort the lens towards the flattening. Following the logic of the law of conservation of energy, CM can perform mechanical work only when its reduction, transforming the potential energy of rest in the kinetic energy of motion - the energy of deformation of the lens. The latter should be a more convex and purchase a stock of potential energy - energy deformations only when directly in contact with CM. In practically, as a result of such contact we could get the clinical picture of cyclo-lenticular block, and healthy eyes we have never witnessed. It becomes quite clear that the theory of the Helmholtz initially enters into irreconcilable contradiction both with the laws of the State of normal physiology and the law concerning the conservation of energy, which determines the unworkable.

The third Contradiction. Normal spherical lenses have feature aiconic action - positive lenses increase and negative lenses reduced the retinal image. Organum of visual are Self-regulating and self-tuning function system (SFS), in which the threshold of 0.2 order incentives are signal errors in the system of dynamic refractive to bring it back to its original state. Signal errors, it would seem, must be followed by a correction reply of the CM to change the curvature of the lens so as to neutralize aiconic action and restore the real retinal image. However, this is not the case, despite an adequate amount for this absolute accommodation of the eye.

Thus, identified by the Helmholtz theory of contradictions discovered, that the CM or so-called "acсomodation muscle", in our view, the eye does not have accomodation and accomodation in Helmholtz is fundamentally impossible. What is the true role of the CM in the eye?

The CM is made up of the following portions of the SM fibers: 1) meridional - muscle Brukke, 2) circular - muscle Mueller, and 3) radial-fan shaped - muscle Ivanov.

The eye is an optical system centered the cornea and the lens axis coincide and form a unified visual axis, strictly focused on central retinal holes. Therefore, any violation of the provisions of the visual axis mutual inevitably would lead to their nonagreement and loss of clarity of the retinal image, for example, under the influence of inertial forces on the mass of the lens with eye movements or sudden and rapid human movements in space (tilt the torso down, jumping, circular rotation, etc.). That is not the case, because SFS eye initiates reflex reduction and tonic radial fibers of muscle Ivanov in the direction opposite to the vector of inertial forces, which is a correction and stabilization of optical components of the visual axis.

Optical system of the eye is not ideal and has varying degrees of manifestation astigmatic fields the cornea and lens. Mismatch between the location of planes these fields can have a negative effect on the quality of the retinal image, especially when abrupt movements of eyes or dramatic and rapid human movements in space. However, and this is not actually. Consider the familiar to all figure, which is a raster pattern, consisting of a regular ring structures incorporating located. Because the orderly layout retina also are a kind of screen when their imposition of a dynamic optical phenomenon, reminiscent of the "consideration" Gajdinger. Recent commit fluctuation amplitude up to 15-20 degrees, which, in our view, can be evidence of mobility around its axis freely suspended cyliar fibres of the lens. The position of the last, and thus his plane on the plane the cornea astigmatic fields may be changed under the influence of inertial forces, hurting the quality of retinal image. SFS eyes and initiates reflex reduction and fan-shaped muscle fibers tonic clonic seizures tenz of muscle Ivanov in the direction opposite to the vector of inertial forces, which is a correction and stabilization of the opposite astigmatic fields.

Thus, muscle Ivanov, as part of the CM, can exercise the function of retinal images during clear of sudden and rapid eye movements, including with the movements of the human in space. This function may be attributed to an act of accomodation of the eye. What is the role in eye accommodation CSM?

The main distinctive physiological property of the CSM:

1) strong and long cut fibers CSM leads to residual muscle contractures, when fibre CSM first relax completely, and their original length is restored only after some time;
2) depending on the conditions under which the reduction CSM, there are two modes of operation - dynamic, the least expensive energy and static, the most expensive energy;
3) tone and motor functions of all CSM are governed by impulses from the somatic subcortical and cortical motor centres, and, therefore, may follow a determined human efforts, and therefore amenable to training;
4) static work CSM helps it working hypertrophy, whereas the dynamic work of muscles to hypertrophy does?nt;
5) as a result of the intensive work of CSM is fatigue - temporary lowering of workable organ, vanishing after a short-time rest. The muscle did not tiring themselves since much earlier to tire their neuromuscular blockade which prevents sinapsy, muscle wasting. Earlier tire subcortical and cortical motor centres (central inhibition by I.M. Sechenov), as evidenced by the significant decrease of efficiency and functional impairments during hard mental work, especially in children.

Let's look at the most likely, in our opinion, biomehanic of accomodation normal eyes with CSM. In this regard, it should be emphasized that the work of the human eye for near are not typical. On the nature of the human eye is arranged in such a way as to provide a clear vision in the range of distances from the tips of fingers outstretched and indefinitely without any stress and fatigue. This was due to the efficiency of visual function to watch in order to preserve the human species.

Normal adult eye is analogous to a simple camera with less than 30 mm short-fokus lens. This optical system even when fully open orifice of diafragm (≥ 10.0 mm) requires almost no interference on the sharpness in the range from 0.6 m to infinity - 1.0 by a large depth of field space objects. Normally, a clear vision of human diversity-remote objects can also come from natural large depth cutting frustum of the optical system of the eye without any participation whatsoever SM pupil and CM, as well as CSM. The pupil, is not so much the diafragming function as a regulator of the intensity of the light falling on the retina of the eye.

To ensure clear vision at smaller distances, ranging from 0.6 to 0.3 m -0.5 -1.0 (optimal area proximate vision - OAPV) - is it necessary to increase the depth of field by reducing the size of the pupil (similar to reduce the orifice in the camera) to 2-3 mm from the friendly pupil-convergent reflex (PKR). The energy costs of convergent group CSM and the SM of the pupil insignificant.

A clear vision to even smaller distances - less than 0.3-0.5 m - extremal area proximal vision (EAPV), in our view, can only be achieved through convergence with the corresponding linear deformation eyeballs in axial direction and offset the retina to back (transformation of the primary form of the eyeball into the secondary), but without the active participation of the pupil, since further reduction of its size in the wild it becomes physiologically impossible. The CSM group OMM is significant of convergent energy costs.

Thus, considered by the biomehanic of accomodation, in our view, the most likely and much in line with the laws of the State of normal physiology, applied and geometrical optics. Act normal human eye accomodation can be implemented and enforced consistently in two visual areas - OAPV (primarily by SM pupil) and EAPV (primarily through the CSM group converged OMM) under the supervision and direction of PKR.

In this topic we would refer to some possible mechanisms of visual fatigue, "spasm of accomodation" and acquired myopia.

The most vulnerable are those with strong fatigue unstable and weak types of higher nervous activity, are more inclined to a variety of stresses and somato-vegetation disorders including disorders of visual functions. This is especially true for children.

On the basis of age-appropriate visual analyzer to solve a task to identify a visualization, it follows that a child have the elementary form of perception, while adult - integrated. During normal vision adult to read one line of typed text book spends 2-3 sec (200-300 words per minute), which is considerably less time reading the same amount of text of the child . Because of the imperfections and gaps of the central nervous system, the child has to closely examine each word to get a holistic picture and identify him. The OMM work dominated in the static mode. The long and intensive visual work in this mode causes a rapid loss of efficiency of muscles, fatigue propulsion points cortex and "the visual fatigue". The latter is accompanied by loss of clarity of vision that encourages child bring the object to the eyes - in EAPV, thereby increasing the volume of convergence and closing the "vicious circle". An adult person during visual work oculo-motor apparatus operates mainly in the dynamic. Therefore, "the visual fatigue" among them is less. Thus, in our view, can develop "the visual fatigue ".

Visually-intensive work CSM, especially in EAPV, it was muscular contractures develop residual, which can significantly slow transformation of the secondary form of the eyeball in the primary, and thus slow down the installation of the optical system of the eye to the clear vision of distant objects. This is especially noticeable for students sitting at her desk in class, the latter indicating short-term impairment when averts on the board after visually-intense work in the vicinity. In doing so, watch the friendly increase pupils as a result of oppression due to fatigue the OKR impellent nervous center. This is functional, transitory and quickly disappears after rest or after all known gymnastics for the eyes. Thus, in our view, could be a "spasm of accomodation" or "false myopia", the most probable cause of residual muscle contractures CSM.

Visually-intensive work CSM, especially in EAPV can lead to accumulation of residual deformations of the sclera and the secondary form of an eyeball with the disagreement of his optical system toward short-sightedness. Clinically this expresses in steady decrease of visual acuity into the distance and comfort (adapted) vision in the vicinity. Thus, in our view, could be the initial stage of true or acquired myopia, which is already irreversible.

Visually-intensive work CSM, especially in EAPV, can lead to overgrowth that against the background of growing child's organism can serve as a stimulus to widen and consolidate the linear deformations of the sclera and the increase of axial size of an eyeball, and hence to the progression of myopia. In this scenario, in our view, acquired myopia can progress.

Conclusions.

1) A clear vision of the diversity of deleted objects in norm by within the naturally large depth cutting frustum of the optical system of the eye. The pupil, is not so much the diafragming function as a regulator of the intensity of the light falling on the retina of the eye.
2) Human eye accomodation act in norm can be realized only in two visual areas - OAPV (primarily by SM pupil) and EAPV (primarily through the CSM group converged OMM). The act of accomodation is under the control and direction of PKR and therefore subject to strong human and susceptible to training efforts.
3) Smooth muscle Ivanov, as part of the CM, can perform the function of adjustment and stabilization of the retinal image clarity during the sharp and rapid eye movements, including with the movements of the human in space.
4) Cause "visual fatigue" may be availability OMM related oppression of cortical and subcortical oculo-motor areas of the brain.
5) "Spasm of accomodation" can be caused by residual muscle contractures CSM convergent group OMM and oppression PKR.
6) Acquired myopia may be caused by consolidating residual deformations of sclera caused by convergent group OMM.
7) Triggering factor in the progression of myopia can be hypertrophy CSM convergent group OMM.

Information about author:

Shurkin V.I. - Ophthalmologist superior

LITERATURE

1. Avetisov E.S. "Myopia". Moscow, 1986.
2. Babskij E.B. etc. "Human physiology". Moscow, Medicine, 1972.
3. Tamickij E.D., Gorbatov V.F. "Training book on photography". Moscow, light industry, 1977.
4. Greenstein A. M., Popova N.A."Vegetative syndromes." Moscow, Medicine, 1976.
5. Davydov V.V. etc. "Psychological dictionary". Moscow, Pedagogy, 1983.
6. Landsberg G.S. "Physics". Moscow, Nauka, 1976.
7. Triumphs A.V. "Topic diagnosis of nervous system diseases". Leningrad, 1964.

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