The Cause of Cataracts P.4



                                                                                                                                                                                                                                                                                                                          

CONTENTS of this PAGE

 

Results

 

 

 

(3) Accommodation causes destruction of a human lens.

 

 

 

1. A somewhat deep understanding of accommodation of the eye

 

 

2. “Excessive accommodation”

 

 

3. “Unreasonable accommodation”

 

 

4. The first incident brought about by the EXCESSIVE: Worsening of myopia

 

 

5.  The last result of the EXCESSIVE:
  The “distorted lens”

 

 

6.  The UNREASONABLE POWER causes
  wedge-shaped cataract
.

 

 

<The power of the ciliary muscle>

 

 

<The power of the capsule>

 

 

<The power of the capsule at the age 8 and
   at the age 60>

 

 

<The UNREASONABLE POWER works
   on the equator.>

 

 

(3) Accommodation causes destruction of a human lens.

 

1. A somewhat deep understanding of accommodation of the eye

 

The word “accommodation” in ophthalmology means “adjustment,” especially that of the eye for various distances (see illustration).1” The word “accommodation” generally means “a place for someone to stay.” In this paper, I use only the word “accommodation” in the specialized meaning. I try not to use other words such as “accommodative,” “accommodate.” By the way, now I am planning to stay in Göteborg at a hotel which accommodates only twenty guests.

 

Fig.3-1 Changes during accommodation1 from DORLAND'S ILLUSTRATED MEDICAL Dictionary

 

John Parr describes the lens. (Fig.3-1) “The lens provides the adjustable part of the eye's refractive power. It lies behind the aqueous and in front of the vitreoustogether with its suspensory zonule and the ciliary body.” “It is about 9 mm in diameter, about 5 mm thick.5” Vitreous : Glasslike or hyaline; often used alone to designate the vitreous body of the eye.1

Vitreous body: The transparent gel that fills the inner portion of the eyeball between the lens and the retina.1 Ciliary body: The thickened part of the vascular tunic of the eye.1 Zonule: A ciliary fiber.1

Robert A. Moses explains the mechanism of accommodation of an eye, as follows.

“The lens capsule tends to mold the lens to a spherical shapebut this is opposed by the tension of the zonular fibers that suspend the lens from the ciliary body. Traction of the zonule on the lens capsule flattens the lens. The ciliary body is stretched backward and outward along the sclera by the elastic choroid. Contraction of the ciliary muscle pulls the choroid forward and the ciliary attachment of the zonule inward toward the lens reducing the tension in the zonule and allowing the lens to increase in convexity,” and “increase in convexity of the lens increases its dioptric power and allows near objects to be imaged clearly on the retina.6” (Fig.3-2)

Sclera: The tough white outer coat of the eyeball.1 Choroid: The thin, pigmented, vascular coat of the eye.1 Dioptric: To more convex shape. Zonular fiber: Zonule.1

The zonula, or the ciliary fibers, are in the zonular spaces. (Fig.3-3) The ciliary body links to the choroid which is located between the sclera and the retina. The ciliary muscle in the ciliary body surrounds the lens like a ring.

 

Fig.3-2 The ciliary muscle by Robert A. Moses6

 

 

If the muscle tenses, the ciliary fibers relax. Accordingly, the thickness of the lens increases. As a result, the eye is focused on a nearby object. In the state of accommodation, the powerful ciliary muscle pulls the choroid toward the lens. The whole of the ciliary body itself moves toward the lens with the choroid. (Fig.3-2)

If the muscle relaxes, the ciliary fibers tense. Accordingly, the lens flattens. As a result, the eye is focused on a distant object. In non- accommodation, the choroid pulls the whole of the relaxed ciliary body and the powerful capsule via its strong contraction.

 

Fig.3-3 A horizontal section of an eyeball by Moses7

 

 

It is necessary to understand the structure of a human lens. (Fig.3-4) The capsule envelopes the entire lens. An epithelium of the lens is beneath the anterior capsule, but no epithelium is under the posterior capsule. The cortex of the lens is composed of lens fiber cells. The center of the lens is the nucleus. The cortex envelops into the nucleus.

Anterior epithelium cells repeat cell divisions over again, and they advance toward the equator of the lens by degrees. Around the equator, the epithelium cell begins to transform into a fiber cell. In the process of transformation, the cell loses mitochondria and other organelle.

Mitochondria: Small spherical to rod-shaped components found in the cytoplasm of cells They are the principal sites of the generation energy (ATP).1 Organella: A specific particle of membrane-bound organized living substance present in practically all cells.1 ATP: adenosine triphosphate, a nucleotide compound occurring in all cells, where it represents energy storage.1

Fiber cells lose those nuclei finally. In this course fiber cells go deep into the cortex by degrees. In this way, the lens fiber cells go on accumulating toward the nucleus.

 

Fig.3-4 The lens by Richard S. Snell and Michael A. Lemp7

Ciliary fibers attach to the equator region of the capsule. Because of the strong elasticity of the capsule, when the zonule relaxes, the thickness of the lens increases. The capsule tends to warp by its own elasticity. Ciliary fibers attach to the ciliary body between the ciliary processes.7

 

We do accommodation unconsciously. When we look at an object naturally, there must be no problem for the accommodation. However, in some conditions, problems arise with the accommodation. Because of it, the eye will be destroyed. I named that “prohibited accommodation.”

I think there are two kinds of prohibited accommodation. I called the first prohibited accommodation “excessive accommodation.” I named the second “unreasonable accommodation.”



2. “Excessive accommodation”

 

 This is the accommodation when a person looks at an object at a distance nearer than 30 cm at an age under about 40.

The distance of 30 cm, or about 1 foot, is a very important distance for an eye. When an eye looks at an object at this distance, its accommodation power of 3.3 diopters is used. The power of 3.3 diopters of the eye is converted into 3.0 diopters of spectacles optically. “Diopter” is “the refractive power of a lens with a focal distance of one meter.1

That is,

Diopter = 100 cm / focal length cm

From now, we use the abbreviation D for the unit of “diopters.” In a myopic eye, the (-) sign is put before the number of diopters. In case of a small number of farsighted eyes, the (+) sign is put before the diopter number. Since near vision is talked about in this paper, the (+) sign is put before all numbers of diopters. But I will omit all those signs.

At the distance of 30 cm, the eye can see the detail of the object sufficiently, because it is not too distant. Besides, the eye can get enough of the area of the near object into view, because the distance is not too near. It is a suitable distance for the eye to see a wide area of the near object. The distance of 30 cm is the perfect distance to see nearby objects in both minute detail and as the whole. Therefore, the distance of 30 cm must be a very important distance for the eye.

 When the eye looks at an object nearer than 30 cm, it uses accommodation power of more than 3.3 D. This is “excessive accommodation.” From now on, we will refer to “excessive accommodation” as “EXCESSIVE.”

 

3. “Unreasonable accommodation”

 

This is the accommodation in the age of presbyopia when a person looks at an near object at a distance of 30 cm or more without proper reading glasses. In the reprinted diagram Fig.3-5, maximum accommodation power decreases with age. The “amplitude of accommodation” in Fig.3-5 means the range of the maximum accommodation power at each age, and the “mean” in the diagram is median maximum accommodation power. I added a line labeled 3.3 D to the original diagram Fig.3-5. From now on, we will refer to “accommodation power” as “POWER.”

At the age of 41, if the eye still has a maximum POWER of more than 3.3 D, the eye can still look at an object at the distance of 30 cm. However, if at the age of 41 the eye has a low maximum POWER of just 3.3 D, then it can barely see an object at the distance of 30 cm. After that age, the POWER continues decreasing. Presbyopia is the situation where an eye cannot see an object at the distance of 30 cm or less. I define presbyopia as this. Therefore, we call the age of 42 or older, “the age of presbyopia.”

 

Fig.3-5 Amplitude of accommodation by Robert A. Moses6

The maximum POWER at each age will never mean always permissible volume of accommodation. In Fig.3-5 by Robert A. Moses, for example, the median maximum accommodation power at the age of 20 is 12 D. But, if a 20-year-old person continues looking at objects using a POWER of 12 D, her eye's load gets extremely heavy. This is because 12 D is the power an eye uses when it looks at an object at the distance of only 8 cm. The normally usable POWER is considered at most 3.3 D. From now on, we will call the “median maximum accommodation power” “MmPOWER.”

In Fig.3-5, the power of accommodation decreases rapidly with age. At the age 46, the MmPOWER falls to about 3.3 D. After that age, the power of accommodation decreases more, and at the age of 50, the MmPOWER decreases to 2.0 D far less than 3.3 D. When we see how human POWER decreases, it is conceivable that the expected life span of the human lens is about 50 years.

 

In the age of presbyopia, the accommodation to look at an object at the distance of 30 cm or less is “unreasonable accommodation.” At an age over 41, we should not use this “unreasonable accommodation.” This causes problems for the eye. Even if the eye attempts this “unreasonable accommodation,” it cannot accomplish accommodation. The eye only uses its power, and it is unable to see the object which it has attempted to see. Therefore, I call the power the “unreasonable power of accommodation.” This causes problems.

 

4.  The first incident brought about by the EXCESSIVE: Worsening of myopia

 

In diagrams Fig.3-6 and 7, arrows indicate the pressure on the lens caused by the capsule. In the EXCESSIVE, as an eye looks at an object at a distance nearer than 30 cm, the lens capsule presses the lens excessively. The pressure working in this accommodation is “excessive pressure.”

 

Fig.3-6 The lens capsule presses the lens. (a side view)


Fig.3-7 The lens capsule presses the lens. (a front view)

Pressure has no direction, it only has strength. But in most cases in this paper, I use the word “pressure” as a pressing power which has a direction.

In a human lens, the nucleus gets harder with age. Accordingly, it gets difficult to return from the state of increased convexity by near vision.  As a result, myopia of the eye gets worse. This process is the cause of worsening of myopia at the age of 16 or older.

In childhood, between the ages of 6 and 15, myopia worsens because the length of the eye ball increases with age. It is only growth of the eye. Including age-related cataract and myopia, the affairs which concern human lens are full of riddles. Therefore, the investigation of myopia is in chaos, like with cataracts. I think the cause of worsening of myopia in a person over the age 15 is the change of the lens shape by the EXCESSIVE. If the refractive power of a human lens increases drastically from the excessive PRESSURE, in the situation that a lens nucleus hardens, it becomes difficult for the lens to return to the original shape. I think this is adult myopia. In this way, the EXCESSIVE worsens the myopia.



5.  The last result of the EXCESSIVEThe “distorted lens”

 

The lens nucleus becomes hard with age. KR Heys said as follows.  “There was a pronounced increase in lens stiffness over the age range from 14 to 78. In the nucleus, stiffness values varied almost 1,000 fold over this age range, with the largest change observed in lenses between the ages of 20 to 60.8” The lens nucleus goes on stiffening steadily with age. By the EXCESSIVE, if the convexity of a human lens continues to increase for a long period of time, adult myopia worsens and, last of all, the lens loses the shape of an optical lens. It is what I call a “distorted lens”. In this state, the shape of the lens has been broken down, and it is in the terminal point of adult myopia. Because the lens cannot be focused on anything, the eye will not get enough sight even if corrected by eyeglasses.

It is assumed that when a change of the lens shape has gone beyond its limit by the worsening of myopia, a “distorted lens” occurs. This comes after the lens had become hard to change the shape for seeing near objects. When an eye develops to a “distorted lens” by the EXCESSIVE, as the eye seems to have no remarkable disorder, ophthalmologists diagnose the eye's low vision as “an unknown cause.” And next, the ophthalmologist diagnoses the low vision as nuclear cataract. The eye will be operated as a cataract.

 We must avoid the EXCESSIVE.

 

Fig.3-8 Human lens growth with age by Harding3

 

Although the size and volume of a human lens changes with age, it is strange that the lens seems to keep its shape and that the degree of refraction does not alter with age. (Fig.3-8)

 

 The “distorted lens” comes about mainly by the EXCESSIVE, and the unreasonable power of accommodation also leads to this state. From now on we call the “unreasonable power of accommodation” “UNREASONABLE POWER.” We consider the cause of the “distorted lens” in the age of presbyopia is the UNREASONABLE POWER.

 After the age of 60, in a human lens which cannot get enough visual acuity, a border between the lens cortex and the nucleus sometimes forms a bumpy, brown membrane. I think it is the wrinkled surface of the nucleus. It must be a symptom of the “distorted lens.” It suggests that even a considerably hardened nucleus has been distorted by the PRESSURE. Thus, the PRESSURE destroys the lens.

 

6.  The UNREASONABLEPOWER causes wedge-shaped cataract.

 

<The power of the ciliary muscle>

After the nucleus has increased stiffness with age to a certain degree, the UNREASONABLE POWER begins to cause an incident other than the “distorted lens.” This is the “destruction of the lens.” It is the wedge-shaped cataract.

The lens cortex is sandwiched between the capsule and hardened nucleus. If an eye at the age of presbyopia looks at an object at the distance of about 30 cm without reading glasses, the lens cortex is pressed by excessive power from the capsule. This power is the UNREASONABLE POWER.

The lens nucleus continues becoming increasingly stiff, meanwhile the power of the capsule, or the elasticity of the capsule, decreases with age. Though, it is conceivable that the ciliary body keeps its power through the life. In this situation, even if the ciliary muscle tenses excessively, the required change to a more convex shape of the lens cannot be accomplished.

Moses writes as follows.

 Measurements of ciliary body movement in accommodation appear to show that the same movement is required per diopter of accommodation at all ages tested.6

E.A. Hermans et al. wrote as follows. Preservation of the net force delivered by the extralenticular ciliary body indicates that the causes of presbyopia must be ascribed to lenticular changes.9” Lenticular: Pertaining to the crystalline lens.1

   The power of the ciliary muscle does not decrease.

 

<The power of the capsule>

R. F. Fisher states, “in childhood Young's Modulus of elasticity is about 6 x 107 dyn/cm2 and decreases to 3 x 107 dyn/cm2 at 60 and 1.5 x 107 dyn/cm2 in extreme old age.10

Although the elasticity of the lens capsule decreases with age, the power of the capsule will be strong.

 

<The power of the capsule at the age 8 and at the age 60>

The Young's Modulus of elasticity value at the age of 60 is 3 x 107 dyn/cm2. The value at the age of 8 is about 6 x 107 dyn/cm2. We assume the child is 8 years old. In the diagram Fig.3-5 by Moses, the MmPOWER at the age of 8 is about 14 D. It is conceivable that if the lens does not increase in stiffness, the MmPOWER might be in proportion to the Young's value at each age. Therefore, as the value at the age of 8 is about 6 x 107 dyn/cm2 and that at the age of 60 is 3 x 107 dyn/cm2, if the MmPOWER at the age of 8 is about 14 D, the MmPOWER at the age of 60 must be 7 D.

If the lens does not increase in stiffness, a person at the age of 60 must be able to look at an object at the distance of 14 cm with the power of 7 D. Though, in the diagram Fig.3-5, at the age of 60 the real power of accommodation is almost zero. This fact says that, although a 60-year-old eye cannot look at an object at the distance of 30 cm, the eye uses the maximum power of accommodation of 7 D. This power will destroy the eye. This is the UNREASONABLE POWER.

 

  <The UNREASONABLE POWER works on the equator.>

In the eye of the age of presbyopia, the accommodation corresponding to the power does not work. But the power of accommodation continues to be used by the capsule. This power is the UNREASONABLE POWER. In a young eye, the pressure put on the lens in accommodation will disperse into the whole of the lens. This is because the lens of a young eye is still soft. However, the lens of an aged eye has become hard. Therefore, in the aged eye, the cells on the equator receive all of the pressure.

Wedge-shaped cataracts occur in such circumstances. The immoderate PRESSURE, or the UNREASONABLE POWER brings about crush of the cells on the equator.





The Cause of Cataracts P.4