But why do you bother?

People is getting cures.

Now another friend with CONICAL CORNEA uncorrected even by 6 dioptres
of convex lens has having flashes of NORMAL SIGHT at three meters with
that eye, reading the 10 line at 10 feet on the black chart. The other
eye has 20/10 vision.

This guy is very much intelligent, and after a little bit of
awkwardness at beginning of treatment, he started seriously to exercise
his own imagination and got great progress.

DO you know what is a conical cornea?

To the other super-idiot from China (a great country with many young
children, it is normal that some of them are idiots) I must tell that
the link works very well.

Here is the abstract

Presbyopia: Cause and Treatment
Last Updated: February 21, 2005
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Synonyms and related keywords: vision loss, visual deficit

     AUTHOR INFORMATION     Section 1 of 10    Click here to go to the next
section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

Author: Ronald Schachar, MD, PhD, President and CEO, Presby Corporation

Ronald Schachar, MD, PhD, is a member of the following medical
societies: American Academy of Ophthalmology, American Association for
the Advancement of Science, American Medical Association, American
Society of Contemporary Ophthalmology, Phi Beta Kappa, Sigma Xi, and
Texas Medical Association

Editor(s): Stephen D Plager, MD, FACS, Chief, Department of
Ophthalmology, Dominican Hospital; Assistant Clinical Professor,
Department of Ophthalmology, Stanford University Hospital; Donald S
Fong, MD, MPH, Assistant Clinical Professor of Ophthalmology, Director,
Clinical Trials Research, Department of Ophthalmology, Southern
California Permanente Medical Group; J James Rowsey, MD, Consulting
Staff, Department of Corneal and Refractive Surgery, St Luke's
Hospital; Lance L Brown, OD, MD, Ophthalmologist, Regional Eye Center,
Affiliated With Freeman Hospital and St John's Hospital, Joplin,
Missouri; and Hampton Roy, Sr, MD, Clinical Associate Professor,
Department of Ophthalmology, University of Arkansas for Medical
Sciences

Disclosure
     INTRODUCTION     Section 2 of 10   Click here to go to the previous
section in this topic Click here to go to the top of this page Click
here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

The scleral expansion band procedure for the surgical reversal of
presbyopia (SRP) is a new technique. The scleral expansion band
procedure has been developed for SRP. The effects of the scleral
expansion band are based on a recently developed theory by Schachar
that states that the crystalline lens is under increased equatorial
zonular tension during accommodation. An understanding of demonstrable
clinical effects of the scleral expansion band procedure, based upon
Schachar's theory, requires a revision of historically held views
concerning the mechanism of accommodation.
     HELMHOLTZ'S THEORY OF ACCOMMODATION     Section 3 of 10   Click here to
go to the previous section in this topic Click here to go to the top of
this page Click here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

According to Helmholtz, during accommodation, when the optical power is
greatest, the zonules are relaxed and the crystalline lens can shift.
The lens would not be stable while reading or examining close objects.
The instability of the crystalline lens during near vision did not seem
physically correct. When viewing through an optical system, the higher
the magnification, the more stable the system needs to be.

According to Helmholtz's hypothesis, since the equatorial diameter
increases with age (ie, since the crystalline lens equator is getting
closer to the ciliary muscle), the zonules should relax. As one ages,
the power of the crystalline lens should increase while viewing distant
objects in the accommodated state. One should become more myopic and
the crystalline lens should become unstable, but in fact, one becomes
slightly hyperopic and the crystalline lens remains stable. Helmholtz's
theory also is not consistent with the decrease in spherical aberration
that occurs during accommodation.

Helmholtz attributes the universal linear decrease in the amplitude of
accommodation with age to hardening of the crystalline lens. No tissue
in the body uniformly hardens in a linear fashion with age. During
cataract extraction, it commonly is observed that crystalline lenses
have different degrees of hardness and no uniform loss of water content
of the crystalline lens with age has been demonstrated. Even in those
cataracts that have a hard nucleus, the cortex is soft.
     SCHACHAR'S THEORY OF ACCOMMODATION     Section 4 of 10   Click here to
go to the previous section in this topic Click here to go to the top of
this page Click here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

An outward equatorial displacement of the crystalline lens produces
central steepening. This counterintuitive phenomenon is demonstrated
readily by pulling on the equator of a biconvex air-filled Mylar
balloon and observing that the reflections from the center of the
balloon become smaller, or minify, (see Picture 2), and the reflections
from its periphery enlarge (see Picture 3).

The equatorial displacement of the crystalline lens occurs as a result
of increased tension on the equatorial zonules (see Picture 4),
produced by contraction of the anterior radial muscle fibers of the
ciliary muscle (see Picture 5, Picture 6). Since an active force is
involved in accommodation, the amount of force that the ciliary muscle
can apply is dependent on how much the ciliary muscle is stretched.

The crystalline lens is of ectodermal origin and continues to grow
throughout life. Except for the progressive myope, the dimensions of
the scleral shell do not change significantly after 13 years. The
distance between the ciliary muscle and the equator of the lens
decreases throughout life. Therefore, the effective force that the
ciliary muscle can apply to the lens equator is reduced in a linear
fashion with age. The amplitude of accommodation decreases linearly
with age resulting in presbyopia and is a consequence of normal lens
growth.

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Author Information
Introduction
Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation
Augmentation Of Accommodative Function
Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation
Methods For Treating Presbyopia
Pictures
Bibliography

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     AUGMENTATION OF ACCOMMODATIVE FUNCTION     Section 5 of 10   Click here
to go to the previous section in this topic Click here to go to the top
of this page Click here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

Any procedure that increases the distance between the lens equator and
the ciliary muscle should reverse presbyopia. In the mid 1980s, scleral
expansion was performed based on these concepts by making multiple
incisions in the sclera over the ciliary muscle. The scleral incisions
produced accommodative amplitude increases of only +1.25 diopters (D)
in young presbyopes and the effect regressed. Fukuska independently
confirmed these observations and predictions.

In 1992, the first scleral expansion band procedure was performed using
a plastic polymethyl methacrylate (PMMA) circular band sutured to the
sclera (see Picture 6). The results were dramatic. Presbyopic patients
had as much as 10 D of accommodation. Since that time, the scleral
expansion band procedure has been modified and improved, so that now a
separate PMMA segment is placed in each of the 4 oblique quadrants of
the eye (see Picture 8, Picture 9).

To date, the worldwide experience with the scleral expansion band
procedure for the SRP involves more than 500 eyes with a range of
accommodative recovery of 1.3-7 D with a mean of 3.25 D. In general,
the response has been favorable with no change in distance refraction,
best-corrected visual acuity, or axial length. Common adverse effects
that resolve in 6-8 weeks include subconjunctival hemorrhage, transient
astigmatism, fluctuating near vision, and dry eyes.
     COMPARISON OF THE HELMHOLTZ THEORY AND THE SCHACHAR THEORY     Section
6 of 10   Click here to go to the previous section in this topic Click
here to go to the top of this page Click here to go to the next section
in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

The Schachar theory of accommodation has met considerable reaction and
discussion, especially from those subscribing to the Helmholtz theory.
Many past experiments have been published that are in disagreement with
Schachar's conclusions that the crystalline lens diameter increases
during accommodation. A careful examination of these experiments
reveals that a systematic error exists. Movement occurs between the
imaging device and the eye. Measurement of the thickness of the cornea
in the accommodated and unaccommodated states of these experiments
reveals a change in corneal thickness. Since corneal curvature and
corneal thickness do not change during accommodation, these experiments
are flawed and cannot be used to reveal the mechanism of accommodation.

The recent experiments by Glasser and Kaufman are similarly flawed.
Although they placed sutures in the cornea as a reference point,
neither the sutures, nor the corneal Purkinje images, subtract out of
the overlain accommodated and unaccommodated images, demonstrating that
eye movement occurred between the imaging device and the eye. They
stated that the small amount of eye movement observed in their
experiments cannot account for the changes in the crystalline lens size
and configuration during Edinger Westphal or pharmacologic stimulation;
however, they offer no controls to prove that this statement is true.

Interestingly, when they fixated the lateral rectus, so that eye
movement was reduced, they observed that the crystalline lens equator
moved toward the sclera, with anterior and posterior zonular
relaxation. They state that the movement of the crystalline lens
equator toward the temporal sclera is caused by lateral translation of
the crystalline lens. This is mechanically impossible. Since the
crystalline lens is denser than water and vitreous, when the anterior
and posterior zonules are relaxed, the crystalline lens equator can
only move toward the temporal sclera by an active generated force (eg,
by the pull of the equatorial zonules).

The importance of eye movement relative to the imaging device is
exemplified by MRI studies performed on accommodating patients by
Strenk et al. An MRI image of the patient's eye during accommodation
revealed that the eye is turned nasally and that a change in the
configuration of the orbital bones occurred. Therefore, both the head
and eye moved during accommodation.

Measurement of the transverse diameter of the globe, the corneal
diameter, and the equatorial diameter of the crystalline lens in the
unaccommodated and accommodated states, demonstrate that all these
measurements decrease during accommodation. This means that the image
plane of the eye in the unaccommodated and accommodated states was not
the same. Their observations are due to artifact, and any conclusion
that they make concerning the mechanism of accommodation from this MRI
study is not valid. For example, they conclude that the equatorial
diameter of the crystalline lens does not increase with age. Their
conclusion is contrary to actual histologic measurements.

Linear and nonlinear finite element mathematical analyses have been
performed on the human crystalline lens. Nonlinear finite element
analysis is used routinely to reliably predict reality. The
mathematical analysis demonstrates that only equatorial stretching of
the equator of the crystalline lens by the equatorial zonules can
produce the clinically observed increase in central optical power
accompanied by a decrease in spherical aberration.

Scanning electron microscopy has shown the following 3 types of
zonules: anterior, posterior, and equatorial. The equatorial zonules
act similar to a skeletal muscle tendon and are the components that
transduce the force of the ciliary muscle to change the focal power of
the crystalline lens. The anterior and posterior zonules are tense
during distance vision and relax during accommodation. The anterior and
posterior zonules act similar to the ligaments of skeletal joints and
are stabilizing components, predominately for distance vision.

Since only the anterior and posterior zonules can be visualized with a
slit lamp in vivo during accommodation, it is understandable how
incorrect deductions have been made. Investigators have demonstrated
that the crystalline lens is stable and gravity does not affect the
amplitude of accommodation. The equatorial zonules have a separate and
distinct insertion into the ciliary body. The crystalline lens remains
stable because the anterior zonules maintain the same position on the
anterior crystalline lens surface even though the crystalline lens
equator is enlarging with increasing age.

In vivo measurements of the position of the crystalline lens equator of
young human research subjects during pharmacologically controlled
accommodation using high-frequency, high-resolution anterior segment
ultrasound revealed that the crystalline lens moves toward the sclera
during accommodation. The mean movement was 6.8±1 mm/D. This amount of
equatorial movement during accommodation was consistent with the
prediction of the nonlinear finite element mode and demonstrated that
accommodation is a small displacement phenomenon (ie, <5% change occurs
in the equatorial diameter of the crystalline lens during
accommodation).

The small amount of equatorial crystalline lens movement explains the
problems and the systemic errors that have occurred during previous
experiments that try to determine the position of the crystalline lens
equator during accommodation. Eye movements are much larger than the
movement of the crystalline lens equator; therefore, proper controls
are essential to interpret any measurements.

Table 1. Comparison of the Helmholtz Theory and the Schachar Theory
Test     Helmholtz     Schachar     Observation
Small displacement equatorial stretching of the biconvex deformable
lens     Decrease in central optical power     Large increases in central
optical power     Large increases in central optical power
Effect of gravity on the amplitude of accommodation     Yes     No     No
Effect of accommodation on spherical aberration     Increase     Decrease
    Decrease
Change in refraction following presbyopia     Myopic     Hyperopic     Hyperopic
Anterior disinsertion of the ciliary muscle     Myopic     Hyperopic
    Hyperopic
Change in the circular muscle fibers following presbyopia     Atrophy
    Hypertrophy     Hypertrophy
Change in the anterior radial muscle fibers following presbyopia
    Little or no effect     Atrophy

Atrophy
Theory has widespread and new applications     No     Yes

1. Profile of the ocean tides
2. Effect of a magnetic field on a magnetic fluid
3. The shape of normal spiral galaxies
The effect of tight 12-o'clock position cataract wound sutures on the
central curvature of the cornea     The cornea flattens in the vertical
meridian (against the rule astigmatism)     The cornea steepens in the
vertical meridian (with the rule astigmatism)     The cornea steepens in
the vertical meridian (with the rule astigmatism)

For the first time, the theory has predicted methods to surgically
reverse presbyopia, to produce a single element variable focus lens
that can have rapid large optical power changes from small equatorial
displacement, and to treat and to prevent ocular hypertension and
primary open-angle glaucoma. The continued challenge will be to perform
properly controlled experiments and to see how this theory will provide
new tools and better methods for improving the visual performance of
patients.
     HISTORICAL PERSPECTIVE OF THE THEORIES OF THE MECHANISM OF
ACCOMMODATION     Section 7 of 10   Click here to go to the previous
section in this topic Click here to go to the top of this page Click
here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

The healthy, young human (<40 y) or young primate eye can rapidly focus
on near and distant objects (ie, it can change focus or accommodate).
The mechanism by which the eye can accomplish this amazing task has
been speculated upon for centuries. Initially, it was suggested that
the eye was divinely created; therefore, it did not follow known
physical laws of optics.

In 1619, Scheiner, a Jesuit priest, proved that accommodation occurred
as a result of a change in the optical power of the eye and that the
eye obeyed the laws of optics. His experiment easily is duplicated and
consists of making 2 vertical pinholes in a card, which are separated
by less than the diameter of the pupil of the eye. The observer looks
through both holes simultaneously and focuses on a needle held
perpendicular to the plane of the holes. When focusing on the needle,
it will appear single; however, if the observer focuses on a more
distant or near object, the needle will appear doubled. This simple
elegant experiment demonstrates that the eye functions as an optical
system.

The explanation of Scheiner's experiment is demonstrated in Picture 10.
Consider a point source of light as the object. A convex lens converges
the rays of light to a point. By placing a card containing 2 holes
between the point source and the convex lens, only 2 rays are brought
to a focus. If the power of the convex lens is changed, then the 2 rays
are brought to a focus at a different distance. The point source
appears doubled at all other distances. If the card has 3 or 4 holes,
the point source will triple or quadruple.

Some of the most famous philosophers and scientists were interested in
how the eye accommodates. In 1611, Kepler and others thought the
crystalline lens moved forward and backward. In 1677, Descartes
suggested that the shape of the crystalline lens changed. In 1742, Lobe
postulated that the shape of the cornea changed. Sturm and Listing
believed that the eye elongated.

In 1801, Thomas Young, using ingenious experiments, provided evidence
that accommodation occurs as a result of changes in shape of the
crystalline lens. He had very prominent eyes. Without anesthesia (which
had not been discovered yet) he placed a caliper, that had rings
attached to each side, around his eye. With his eye rotated nasally, he
placed 1 ring on his cornea and the other ring over his macula. He
could see a circular entopic ring induced by the ring on his macula. As
he changed his point of focus, the entopic ring did not change size.
This proved that the eye does not elongate during accommodation.

Next, he calculated the amount the cornea would have to move forward to
account for his accommodative amplitude. Using candles and a front
surface mirror engraved with a scale, he did not observe any corneal
movement as he changed his point of focus. He further proved that the
radius of curvature of the cornea does not play a role in
accommodation. He attached a convex lens possessing the optical power
of the cornea to the bottom of an eyecup. He filled the eyecup with
saline and placed it over his cornea (the forerunner of contact
lenses). The saline in contact with the cornea eliminated the
refractive power of the cornea; yet, he was still able to fully
accommodate.

Young demonstrated that accommodation did not occur in aphakes. He
realized that accommodation had to result from a change in position or
shape of the crystalline lens. He was convinced that accommodation
could not occur because of forward or backward movement of the
crystalline lens. He calculated that the crystalline lens would have to
move 10 mm to account for his amplitude of accommodation. This would be
impossible.

Young observed that spherical aberration decreased during
accommodation. He concluded that accommodation occurs as a result of a
change in shape of the crystalline lens. Since the ciliary body had not
been discovered yet, he postulated that the change in shape of the
crystalline lens is induced by a muscular mechanism within the
crystalline lens.

In 1823, Purkinje noted the reflected images of a candle from the
anterior and posterior crystalline lens surfaces. In 1849, Langenbeck
was able to observe in a patient that the Purkinje image from the
anterior surface of the crystalline lens became smaller during
accommodation by using a candle and a magnifying glass. He correctly
concluded that the anterior surface of the crystalline lens becomes
more convex during accommodation. He proposed that the ciliary muscle,
which had been discovered independently by Bruecke and Bowman in 1847,
squeezes the crystalline lens.

In 1851, Cramer followed up on Langenbeck's observation and improved on
it by making a device that incorporated a telescope to allow accurate
observations of the Purkinje images during accommodation. He observed
that the anterior surface of the crystalline lens became more convex,
but the posterior surface did not change shape.

In 1855, Helmholtz improved on the Cramer device by placing crossed
glass plates between the patient's eye and the telescope, so that the
Purkinje images were doubled and could be measured more accurately. In
addition to observing that the anterior and posterior surfaces of the
crystalline lens became more convex, he noted that the lens became
thicker during accommodation. He hypothesized that the ciliary muscle
relaxes during accommodation allowing the lens to become more spherical
under the influence of its own elasticity. According to his hypothesis,
the equatorial diameter of the lens should decrease as it becomes more
spherical during accommodation. He postulated that presbyopia, the loss
of accommodation with age, occurred as a result of lens sclerosis (ie,
loss of elasticity of the lens with age).

In 1864, Donders studied the change of the amplitude of accommodation
with age. He found that the amplitude of accommodation declined in a
linear fashion with age. This decline occurs universally and
predictably. If patients are corrected properly for distance vision,
their age can be determined within 1.5 years by measuring their
amplitude of accommodation. Donders also observed that patients become
slightly hyperopic when they become presbyopic.

In 1901, Tscherning examined the curvature changes of the anterior
crystalline lens surface by observing the changes in the Purkinje
images when 4 lights are used as objects. He placed the lights so that
2 formed reflected images from the central anterior surface and 2
formed reflected images from the peripheral anterior surface of the
crystalline lens. He observed that the central images moved closer
together during accommodation, while the peripheral images moved
further apart. He concluded that the crystalline lens was becoming more
convex centrally but was becoming flatter in the periphery during
accommodation. This was consistent with Young's observation that the
spherical aberration of the eye decreases during accommodation.

Helmholtz's theory did not explain the peripheral flattening of the
crystalline lens without additional assumptions. For example, the iris
constricts during accommodation and it was imputed to produce the
peripheral flattening of the crystalline lens. However, von Graefe had
demonstrated accommodation in a patient with a total iridectomy.

Tscherning postulated that during accommodation the ciliary muscle
exerted tension on the crystalline lens, pressing the crystalline lens
against the anterior vitreous. The resistance of the vitreous
transmitted sufficient force to effect central bulging of the anterior
surface of the crystalline lens. His theory predicts that the central
thickness should decrease during accommodation. He did not accept
Helmholtz's measurements of increasing crystalline lens thickness with
accommodation. Tscherning thought that presbyopia was the result of
enlargement of the crystalline lens nucleus. All subsequent theories
Gullstrand (1911), Fincham (1937) used Helmholtz's hypothesis that the
zonules are relaxed during accommodation. Helmholtz's hypothesis and
subsequent modifications attribute presbyopia to sclerosis of the
crystalline lens stroma or capsule, atrophy of the ciliary muscle, or
stiffening of the ciliary muscle attachments.

Based on these theories for the mechanism of accommodation, the
amplitude of accommodation could be increased only by softening the
lens stroma and/or capsule, rejuvenating the ciliary muscle by somehow
reversing ciliary muscle atrophy, or reversing ciliary body fibrosis.
Since none of these methods are clinically possible there has been no
surgical therapy for increasing the amplitude of accommodation and
reversing the symptoms of presbyopia.
     METHODS FOR TREATING PRESBYOPIA     Section 8 of 10   Click here to go
to the previous section in this topic Click here to go to the top of
this page Click here to go to the next section in this topic
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

Presbyopia initially was treated with near vision optical aids using
magnifying lenses, reading glasses, and monocles. Patients were
constantly removing reading glasses and losing them because the reading
glasses interfere with vision at all other distances. Benjamin Franklin
fused the distance lens with the near reading lens to give us bifocals
that were later modified to trifocals. The problem with these reading
aids is that they only allow sharp near vision at a given distance and
the near visual field is limited by the lens. Patients must learn to
rotate their eyes downward when reading with bifocals instead of
rotating their head. It usually takes 2-3 weeks for patients to get
used to wearing bifocals. Trifocals can even be more of a problem for
many patients.

To avoid the problems of bifocals and trifocals, bifocal contact lenses
have been developed. The bifocal contact lenses generally have been
unsuccessful because the distance and near powers of the contact lens
must be crowded into an area that can barely cover the pupil. The
patient must learn how to shift the contact lens and to ignore the
distant or near image according to the visual task.

Multifocal glasses and multifocal contact lenses also are generally not
satisfactory. Multifocal lenses produce multiple images at various
focal points. Light reflected or emitted by an object must be dispersed
by the multifocal lens over all the focal points. Therefore, the
intensity at any given focal point will be reduced and the contrast
sensitivity diminished. To avoid prismatic effects, the visual field of
a multifocal lens is reduced. In addition, the patient must learn to
select the appropriate image.

The problems with bifocal and multifocal contact lenses forecast the
problems that have, and will continue to occur, with attempts at making
a bifocal or multifocal cornea using LASIK, or using intracorneal
lenses, or phakic intraocular lenses.

Monovision as a treatment for presbyopia generally is accepted by fewer
than 30% of the population. The loss of stereopsis and learning to
ignore a blurry image from one half of the binocular visual field
easily accounts for the patient's distress with monovision.

Summary

Treatments for presbyopia have not been very good because the
physiological mechanism of the crystalline lens has not been restored.
The Schachar theory of accommodation states the following:

1. Increased equatorial zonular tension occurs during accommodation.

2. Presbyopia is due to a decrease in the effective working distance of
the ciliary muscle as a result of normal crystalline lens growth.

Based on this theory the accommodative amplitude of presbyopes can be
increased.

Any technique that increases the effective working distance of the
ciliary muscle, the distance between the ciliary muscle and the
crystalline lens equator, increases the amplitude of accommodation
physiologically.
Table 2. Comparison of Methods for Treating Presbyopia

Focus at Multiple Near Distances

Full Clear Visual Field

Reversible

Large Range of Correction

Effect Regresses

Normal Stereopsis

Negative Cosmetic Implications

Physiological

Involves a Surgical Technique

Halos at Night

Potential for Serious Complications

Reading glasses

No

No

Yes

Yes

N/A

Yes

Yes

No

No

No

None

Bifocals glasses

No

No

Yes

Yes

N/A

Yes

Yes

No

No

No

None

Trifocals glasses

No

No

Yes

Yes

N/A

Yes

Yes

No

No

No

None

Monovision

No

No

Yes

Yes

N/A

No

No

No

No

No

None

Multifocals glasses

Yes

No

Yes

Yes

N/A

Yes

No

No

No

No

None

Bifocal contacts

No

No

Yes

Yes

N/A

Yes

No

No

No

No

Minimal

Multifocal contacts

Yes

No

Yes

Yes

N/A

Yes

No

No

No

No

Minimal

Intracorneal lenses

No

No

Yes

Yes

No

Yes

No

No

Yes

No

Significant

Intracorneal multifocal lenses

Yes

No

Yes

Yes

No

Yes

No

No

Yes

Yes

Significant

Phakic intraocular lenses

No

No

Yes

Yes

No

Yes

No

No

Yes

Yes

Significant

Phakic multifocal intraocular Lenses

Yes

No

Yes

Yes

No

Yes

No

No

Yes

Yes

Significant

LASIK produced bifocal cornea

No

No

No

Yes

No

Yes

No

No

Yes

Yes

Significant

LASIK produced multifocal cornea

Yes

No

No

Yes

No

Yes

No

No

Yes

Yes

Significant

Scleral incisions

Yes

Yes

Yes

No

Yes

Yes

No

Yes

Yes

No

Minimal

Scleral expansion band

Yes

Yes

Yes

Yes

No

Yes

No

Yes

Yes

No

Minimal
     PICTURES     Section 9 of 10   Click here to go to the previous section
in this topic Click here to go to the top of this page Click here to go
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Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

Caption: Picture 1. Keratoconjunctivitis, Atopic
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Caption: Picture 3. Reflection in the periphery of the balloon
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Caption: Picture 4. In the unaccommodated state, all the zonules are
under tension (a). According to the Schachar theory, in the
accommodated state, the equatorial zonules are under increased tension,
and the anterior and posterior zonules are relaxed (b).
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Caption: Picture 5. Schema of the configuration of the eye in the
unaccommodated state.
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Caption: Picture 6. Schema of the configuration of the ciliary body in
the accommodated state according to the Schachar theory.
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Caption: Picture 7. Polymethyl methacrylate band
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Caption: Picture 8. Incisions for placement of the polymethyl
methacrylate band
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Caption: Picture 9. Placement of the polymethyl methacrylate band
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Caption: Picture 10. Scheiner's experiment
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     BIBLIOGRAPHY     Section 10 of 10   Click here to go to the previous
section in this topic Click here to go to the top of this page
Author Information Introduction Helmholtz's Theory Of Accommodation
Schachar's Theory Of Accommodation Augmentation Of Accommodative
Function Comparison Of The Helmholtz Theory And The Schachar Theory
Historical Perspective Of The Theories Of The Mechanism Of
Accommodation Methods For Treating Presbyopia Pictures Bibliography

   * Atchison DA: Accommodation and presbyopia. Ophthalmic Physiol Opt
1995 Jul; 15(4): 255-72[Medline].
   * Bowman: Lectures on the Parts concerned in the Operations of the
Eye. London: 1849:62.
   * Brown N: The shape of the lens equator. Exp Eye Res 1974 Dec;
19(6): 571-6[Medline].
   * Brucke: Arch Anat Physiol wiss Med. 1846:370.
   * Coulombre JL, Coulombre AJ: Lens development. IV. Size, shape,
and orientation. Invest Ophthalmol 1969 Jun; 8(3): 251-7[Medline].
   * Cramer N: Lancet. Vol 1. 1851:529.
   * Descartes R: Traite de l'homme. Paris: 1677.
   * Donders FC: Accommodation and refraction of the eye. The New
Society. London: 1864:204-215.
   * Duke-Elder S, Waybar KC: Anatomy of the visual system. In:
Duke-Elder, ed. System of Ophthalmology. Vol 2. London: Henry Kimpton;
1962:80-1.
   * Farnsworth PN, Shyne SE: Anterior zonular shifts with age. Exp
Eye Res 1979 Mar; 28(3): 291-7[Medline].
   * Fincham EF: Mechanism of accommodation. Br J Ophthalmol 1937; 8:
5-80.
   * Fincham EF: The mechanism of accommodation. Br J Ophthalmol
[suppl] 1937; 8: 1-80.
   * Fukasaku H: Silicone expansion plug implant surgery for
presbyopia. In: Am Soc of Cataract Refractive Surg Symposium. Boston,
Ma: 2000.
   * Fukasaku H: Surgical Correction of Presbyopia. ASCRS Meeting
Seattle, WA; April 1999.
   * Glasser A, Kaufman PL: The mechanism of accommodation in
primates. Ophthalmology 1999 May; 106(5): 863-72[Medline].
   * Glasser A, Kaufman PL: Letter to the editor. Ophthalmology 2000;
107: 626.
   * Gordon AR, Siegman MJ: Mechanical properties of smooth muscle. I.
Length-tension and force- velocity relations. Am J Physiol 1971 Nov;
221(5): 1243-9[Medline].
   * Gullstrand A: Einfurhrung in d. Methoden d. Dioptrik d. Auges d.
Menschen. Leipzig 1911.
   * Ivanoff A: On the influence of accommodation on spherical
aberration in the human eye: an attempt to interpret night myopia. J
Opt Soc Am 1947; 37: 730-1.
   * Kepler: Dioprice. Augsburg: 1611.
   * Kleinman NJ, Worgul BV: Lens. In: Tasman W, ed. Duane's
Foundations of Clinical Ophthalmology. Vol 1. Philadelphia: 1994.
   * Koomen M, Tousey R, Scolnik R: The spherical aberration of the
eye. J Opt Soc Am 1949; 39: 370-6.
   * Langenbeck K: Opthal. Gottingen 1849.
   * Levy NS: The mechanism of accommodation in primates.
Ophthalmology 2000 Apr; 107(4): 625-6[Medline].
   * Levy NS: Letter to the editor. Comparing MRI's with Movement
Artifact. In: Invest Ophthalmol Vis Sci. 2000; Available at
http://www.iovs.org[Full Text].
   * Lim SJ, Kang SJ, Kim HB: Analysis of zonular-free zone and lens
size in relation to axial length of eye with age. J Cataract Refract
Surg 1998 Mar; 24(3): 390-6[Medline].
   * Listing: Wagner's Handworterbuch d. Physiiologie. Braunschweig
1853; 4: 498.
   * Lobe: Dissertatio de ocula humano. Vol 119. 1742.
   * Marshall J, Beaconsfield M, Rothery S: The anatomy and
development of the human lens and zonules. Trans Ophthalmol Soc U K
1982; 102 Pt 3: 423-40[Medline].
   * Neider MW, Crawford K, Kaufman PL: In vivo videography of the
rhesus monkey accommodative apparatus. Age- related loss of ciliary
muscle response to central stimulation. Arch Ophthalmol 1990 Jan;
108(1): 69-74[Medline].
   * Purkinge: Beobachtungen u. Versuche z. Physiologie d. Sinne.
Prague 1823; 2: 128.
   * Rafferty NS: Structure, function and pathology. In: Masel H, ed.
The Ocular Lens. New York: Marcel Dekker; 1985: 2-5.
   * Sakabe I, Oshika T, Lim SJ: Anterior shift of zonular insertion
onto the anterior surface of human crystalline lens with age.
Ophthalmology 1998 Feb; 105(2): 295-9[Medline].
   * Schachar RA, Anderson DA: The mechanism of ciliary muscle
function. Ann Ophthalmol 1995; 27: 126-32.
   * Schachar RA: US Patent Numbers: 5,354,331; 5,465,737; 5,489,299;
5,503,165; 5,529,076; 5,722,952 . European and other patents pending.
   * Schachar RA: Cause and treatment of presbyopia with a method for
increasing the amplitude of accommodation. Ann Ophthalmol 1992 Dec;
24(12): 445-7, 452[Medline].
   * Schachar RA: US Patent Number 6,007,578 . European and other
International Patents pending.
   * Schachar RA, Huang T, Huang X: Mathematic proof of Schachar's
hypothesis of accommodation. Ann Ophthalmol 1993 Jan; 25(1):
5-9[Medline].
   * Schachar RA, Bax A: The mechanism of human accommodation as
determined by non-linear finite element analysis. (To be submitted).
   * Schachar RA, Cudmore DP: The effect of gravity on the amplitude
of accommodation. Ann Ophthalmol 1994 May-Jun; 26(3): 65-70[Medline].
   * Schachar RA: Zonular function: a new hypothesis with clinical
implications. Ann Ophthalmol 1994 Mar-Apr; 26(2): 36-8[Medline].
   * Schachar RA: Histology of the ciliary muscle-zonular connections.
Ann Ophthalmol 1996; 28: 70-9.
   * Schachar RA, Tello C, Cudmore DP: In vivo increase of the human
lens equatorial diameter during accommodation. Am J Physiol 1996 Sep;
271(3 Pt 2): R670-6[Medline].
   * Schachar RA: Is Helmholtz's theory of accommodation correct? Ann
Ophthalmol 1999; 31: 10-17.
   * Schachar RA, Cudmore DP, Black TD: A revolutionary variable focus
lens. Ann Opthalmol 1996; 28: 11-18.
   * Schachar RA, Cudmore DP, Black TD, et al: Paradoxical optical
power increase of a deformable lens by equatorial stretching. Ann
Ophthalmol 1998; 30: 10-18.
   * Schachar RA: The scleral expansion band procedure for the
treatment of ocular hypertension and primary open angle glaucoma. Ann
Ophthalmol 2000; 32: 87-9.
   * Schachar RA: Pathophysiology of accommodation and presbyopia.
Understanding the clinical implications. J Fla Med Assoc 1994 Apr;
81(4): 268-71[Medline].
   * Scheiner: Oculus. Innsbruck: 1619.
   * Streeten BW: Zonular apparatus. In: Jakobiec FA, ed. Ocular
Anatomy Embryology and Teratology. Philadelphia: 1982:331-53.
   * Strenk SA, Semmlow JL, Strenk LM: Age-related changes in human
ciliary muscle and lens: a magnetic resonance imaging study. Invest
Ophthalmol Vis Sci 1999 May; 40(6): 1162-9[Medline].
   * Sturm JC: Dissertatio de presbyopia et myopia. Altdorfi: 1697.
   * Tscherning M: Physiological Optics. Philadelphia, Pa: Keystone;
1904:160-89.
   * V Graefe: Presbyopia: Cause and Treatment. Arch Ophthalmol 1860;
7: 150.
   * van Alphan GWHM, Robinette BS, Marci FJ: Drug effects on ciliary
muscle and choroid preparations in vitro. Arch Ophthalmol 1962; 68:
111-23.
   * Vanderploeg JM: Near visual acuity measurements of space shuttle
crew members. Aviat Space Environ Med 1985; 57: 492.
   * von Helmholtz H: Uber die akommodation des auges. Albrecht von
Graefes Arch Ophtalmol 1855; 1: 1-89.
   * Young T: On the mechanism of the eye. Philos Trans Royal Soc
1801; 92: 23-88.

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Presbyopia: Cause and Treatment excerpt

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Wow it's the legendary Rishi.  I remember reading some of your stuff.
You're insane.  But I am too.  Your link doesn't work, idiot.  Anyways,
welcome back.  It's a pleasure to meet you.

so it bothers you that noone wants to engage you in irrational
conversation?
you are a sick pathetic old man.  what other psychological problems do
you have-- do you have a fetish for young children?

Were you breast-fed or bottle fed?

-MT