Natural Vision Improvement V1.1

 
[5.0] THE PROBLEMS

[5.1] What is myopia?

Also called shortsighted, or nearsighted. Myopia is the
inability to see distant object clearly. The physiology is that the
image produced by the eye focuses just short of the retina, leaving a
blured image to fall on the macula.

Textbooks say the physiology can vary, the axial length from the
lens to the retina is too long, or the lens is over
accommodating, or the curvature in the cornea has changed, or the
lenticular curvature has changed. The lens itself may by
displaced of its own accord or the inter occular pressure is too
great. Diabetes is known cause of myopia and general ill health;
stress, emotional problems can bring on temporary conditions.
Some very rare cases result from a genetic pigmentation problem with
the retina.

Conventional optometry regards myopia as a hereditary problem
contrary to evidence to suggest a strong enviromental factor.
COnventional Optometry treats myopia by the use of stronger and
stronger presrciptions.

Behavioral optometry regards myopia as a symptom of vision
imbalance which is often responsive to vision therapy.

Mypoia is measured in negative spherical diopters. ie -1 D. one
diopter is the power of a lens which will focus parallel rays at a
distance of one meter.




[5.2] What is astigmatism?

Astigmatism is the condition where a point focus can not be
formed on the retina. The refraction of light is unequal in
different meridians. This means lines in one one direction may be
blurred while others are not. Astigmatics often report double vision
(diplopia) or even multiple images (polypopia) in both eyes or even
a single eye.

The physiology is as uncertain as that of myopia. The cornea or
lens may not be rotationaly symmetrical, or the eye itself by be
assymetric. The extraocular muscles are sometimes
responsible for deforming the shape of the eye. Conventional
optometry treats astigmatism throught the prescription of
lenses. Behavioral optometry regards astigmatism as correctable with
vision therapy.

Elliot Forrest O.D. found a relationship between head movement,
posture and visual scanning. If you use a computer or read a lot then
you will tend to scan from along the horizontal meridian and neglect
the vertical meridian, with a resultant astigmatism in that
meridian.

Astigamtism may also result from a twisting of the spine, pelvis or
neck. Astigmatics often have a tight or restricted posture and
movement.

You can quickly tell if you are astigmatic with the astigmatic mirror
section [9.21]

[5.2.1] What is the notation for astigmatism?

Astigmatism is measured in cylindrical diopters. Three numbers are
needed. The first number is the power of a spherical lens. The
second is the power of cylindrical lens and the last number is the
principal meridian in degrees for that lens. Facing a patient: 0
degree or 180 degree is horizontal, 90 degree is vertical, 45 is
up right to down left, and 135 degree is up left to down right.

Optometrist usualy use "minus" notation eg +2.25 -0.75 x 175 and
ophthalmologist use "plus" notation eg +2.25 +0.75 x 5 These are the
same measurement.

so is -1.00 +1.00 x 135 and -1.00 -1.00 x 45

The average astigmatic usually has the horizontal meridian
flatter than the vertical meridian.




[5.3] What is hypermetropia?

Also farsighted or longsighted or hyperopia. Hypermetropia is the
condition where the eye tends to focus behind the retina.
Hypermetropia is usually not a problem as small amounts can be
overcome by accommodation. Indeed the majority of people are born
hypermetropic.

The physiology is as poorly understood as with all vision
problems. The eye may be considered too long, the retina may have
detached, accommodation may be insufficient. etc etc etc.


[5.4] What is presbyopia?

Also old age sight. Presbyopia is a failure in accommodation with the
onset of age. It mostly affects near vision, but distance vision is
also sometimes affected.

The physiology of presbyopia is considered to be from change in the
shape and or structure of the lens are commonly blamed. Less commonly
the strength of the ciliary is at fault.

As with all sight problems this is poorly understood.


[5.5] What is emmetropia?

Emmetropia is the ideal eye where a relaxed flattened lens
focuses exactly on the retina. Commonly emmetropia is another word
for normal sight. The emmetropic eye is fully rested and display
no signs of stress when looking at the far point or the near point.

No eye is perfectly emmetropic all of the time.

The opposite of emmetropia is called ammetropia.


[5.6] What is strabismus?

Also "cross-eyes" or, less commonly "squint". A rare condition where
the eye turns in, out, up or down. That is the eyes are no longer
working as a team. Behavioral optometry beleives that the cause
being at a cortical level is treatable. Untreated the condition
lead to many emotive dificulites.

[5.7] What is amblyopia?

Also "lazy eye". A condition where one eye apparently looses
clear sharp vision which cannot be compensated for with
corrective lenses. A condition best diagnosed by a professional.


[5.8] How accurate are visual measurements?

Not very. Vision changes continuously and the autorefraction and
subject refraction tests performed by optometrists and
opthalmologists give only a "snapshot" of your current accuity.
Autorefraction gives a sort of "at rest" measurement and
subjective refraction measures your ability (some people say
"under pressure to perform") to discern what the eyes present to yourmind. A score of 20/20 does not include your acuity at the near
point.

Many other measurements are not covered by a standard optometry
test.

Eye-movement skills, the ability to quickly focus from one
object to another.

Eye-teaming skills, converging and diverging, the ability to turn
the eyes inward and outward in a coherent way.

Eye focusing skills, the ability to make rapid and accurate
shifts in visual inspection with instantaneius clarity and at any
distance. Also the ability to maintain focus on a an object. Focusing
is about expanding the point of vision not about forcing or trying
harder. Effects/reflecfs concentration abilities.

Dynamic visual acuity, the ability the see sharply while an
object or person is in motion.

Peripheral vision, the ability to use side horiztonal and
vetical vision. Used to position yourself in space and time.
Improvements result in better balance and movement.

Binocular fusion, the ability to coordinate the eyes precisely so the
brain can "fuse" the input. Dyslexia is a catch all term to label
crossed and left/right reversal dificulties. It is about a lack of
co-ordination between the left and right hemispheres of the brain and
body. Fusion creates depth perception.

Eye-hand co-ordination. Combining the visual and motor systems, if
the eye movements are jerky then the hand movements will be too.
Effects sprots performance and even handwriting.

Visual form perception. Becoming aware of the shapes features of
sensory information. The ability to organize images on the
printed page into letters and/or words.

Visualization and Visual memory. How you make and store and
recall visual images and imformation. Effects you ability to
learn.


[5.9] How do I measure my own acuity?

To measure acuity with an eye chart: Stand back from an eye
chart. Determine the smallest row you can read. Take the
distance you are standing from the chart (normally 20 feet or 6
meters) and divide that by the number printed next to the line. This
ratio is your acuity. The ability to read black letters on a white
background from twenty feet (6m) is known as "Snellen acuity"
named after the inventor of the eye chart, and is usually
represented with "20" in the numerator. Expressed as a percent, it is
your "percent of normal vision". This percent must not be taken as
an absolute measurement, since one will have different acuities at
different distances.

To measure amount of myopia in diopters: Measure the furthest
distance you can see the letters absolutely clear and black (not just
readable). This is your focal length. If you measure your focal
length in meters, you can compute your refractive error in diopters by
taking the negative reciprocal. For example, if things start to
blur out at half a meter, you have a refractive error of -2.00 D. The
greater the magnitude of this number, the more your myopia. The
number you come up with by this means should represent more myopia
than what the eye doctor would give you as a prescription, since eye
doctors are trained to "under- prescribe".


[5.10] What is average daily vision?

A subjective measurement of how your vision faired during the
day. It is easy to get a good idea of the state of your vision by
using a set of daily landmarks or signs to judge its current state.
You will also find vision varies quite a bit during the day, so you
need to take this in consideration when making your evaluation.
Many people find that vision is directly related to their current state
of alertness and health. As you become tired during a typical day or
are ill your vision reflects this.


[5.11] What is peak daily vision?

Peak daily vision is defined as the "best" subjective point of
clarity throughout the day. Most people are surprised to find just
how good the peak point of vision during the day actually is.


[5.12] Should I keep track of peak and average daily vision in a
diary?

Yes. While this is not mandatory, it helps you see long term
trends, and gives more reliable feedback as you experiment with
changes to your lifestyle and undertake various remedies for your
vision. Changes over weeks and months are difficult to notice until
they reach a large threshold. It is much easier to note down the
state of your vision each day, whether you had any clear flashes and
what duration they were, rather than to rely on your memory. Include
as much detail as you feel necessary. You would also be surpised at how
quickly you adjust to better eyesight and forget what poor vision
was like. Some people improve without realising they have improved.


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