Posted on 30th Jun 2014
Let us remember the Helmholtz mechanism of accommodation. In response to defocusing the image on the retina nerve impulses run through the reduction of parasympathetic part of the oculomotor nerve to the ciliary muscle; muscle contracts; ciliary ligament relax; tension of the lens capsule is reduced; lens due to its elasticity becomes more convex and consequently refracts stronger.
That is, we have a chain: the nerve - muscle - the lens. In
this chain, the gap can occur at any point.
If the lens does not respond
to the tension of the capsule due to the fact that it loses its elasticity - is
presbyopia or presbyopia.
Lens - is a unique organ in our body. Above
all, it is unique that it has no single vessel or nerve. The lens does not hurt,
it can not become inflamed, it feeds from the liquid contained in the chamber of
the eye (aqueous humor). Response to the violation of the chamber moisture it
can be the only way - muddy.
Further, the uniqueness of the lens is that it
is the only organ grows all our lives. Yes, the whole body stops growing by age
25, and the lens continues to grow, but it does not increase its volume. It
grows into itself. Germination zone located under the front surface of the
capsule, the new lens fiber spreading layer under the capsule up to the center
of the rear surface while pushing the center of the previous layers and sealing
them. The result is a more dense core and a flexible lens cortex.
With
age, the nucleus becomes more dense, it is less able to change its shape.
Remember I said that the stock of accommodation is maximal in 15 years, and
18-20 years begins to decrease? So, this is due to condensation nuclei. At age
20, the nearest point of clear vision gradually moved away from the eye, but
until it reaches 30 cm, we do not notice. It can be noted by those who are very
heavy load on your eyes - appears visual discomfort, because the stock of
accommodation decreases. Finally, after 35 years, we were surprised to note that
the newspaper wants to stay farther away from eyes. After 40 years of arm's
length is not enough, and you have to go to the optometrist for glasses for
nearsightedness. Typically, emmetropia (first points discharged between 40 and
45 years.) Available age norms presbyopia. Emmetropia For 40 years rely positive
reading glasses power 1.0 W, 45 years old - 1.5 D 50 years old - 2 , 0 a, 55
years old - 2.5 D 60 years old - 3.0 D 65 years old- 3.5 D.
After 65
years of presbyopia is not progressing, as the lens loses its elasticity, the
cortical substance is almost absent. Consequently, in 70 and 75, and 80 years
and beyond for reading Emmetropia need glasses 3.5 D. Those with hyperopia,
these glasses by age added to the points that are needed for the distance. So
there are people who need glasses for near 4.0 L or 6.0 L, and maybe more. With
myopia of this age norm subtract correction for distance. Therefore,
short-sighted people can read for a long time without glasses.
I want
you, dear my readers understand a simple truth: presbyopia progresses regardless
of our efforts to overcome it, or our attempts to ignore it. While medicine has
not found a way to stop the process of sealing the lens, because its - life,
growth, and uniqueness. Therefore, those who for various reasons do not want to
take the reading glasses and hurt the eyes - nothing but a headache not work.
And to take the points in this case have not with 1.0 D, and with the age norms
with which you give up. How many times I had to warn of fifty patients who
tragically perceived need glasses to read! I subscribe to them +2.0 D glasses,
and they cry out in terror, "No, I have such strong points will not take that
then where will I be in 5 years?" And after 5 years is that supposed to age, ie
2.5 D. and attempts at 50 years old using reading glasses with 1.0 L, give only
a severe headache, which is blamed on migraine, or pressure, or nervous
stress.
Another myth associated with presbyopia, "Just start wearing
reading glasses - and vision immediately begin to deteriorate and have to use
stronger glasses. Better yet, I'll read without glasses. "Now we understand that
the near vision will deteriorate regardless of whether we wear glasses or not.
This is a natural process of maturation of the lens (not to say - aging). And no
need to torture yourself, flirting and concealing age. By the way, I noticed
that men perceive the need for reading glasses more tragic than women. They make
it even harder to hide their age! How many times have I heard from the man: "All
right, now I'm an old man!" - Just because they needed reading
glasses.
So once again: do not be afraid of reading glasses, do not
overload your eyes, do not deprive yourself of pleasure reading, handicrafts,
embroidery, etc. If this process cannot be stopped - why torture yourself?