

I know the details of those eyes, I know their combination gives birth to the
Eternal Mangekyo Sharingan. When Madara was almost blind Izuna gave him his
eyes, the same thing happened with Itachi and Sasuke.

In these two cases we've seen the Eternal Mangekyo Sharingan and here comes my
question:

  1. In the first case, Madara was "blind" and Izuna had the good eyes, the combination was the Eternal. In the second case, Itachi was "blind" and Sasuke had the full eyes, giving birth to the Eternal. So it's indifferent which eye it's transplanted in the host body? (It doesn't matter that the good eye gets a disadvantaged blind eye?) 

  2. As for the main question, how it is realized the "fusion" of 2 different eyes in one eye hole? I don't want to dig myself into the nerve/artery things. I'm interested more likely in the fact that how you mix 2 eyes into one and how the full eye and the blind eye, it's yet so much stronger?? 


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naruto
How does transplanting different sets of Sharingan eyes work?


Over time, use of the Mangekyō Sharingan's techniques deteriorates the user's
eyesight to the point of blindness. Only by taking and transplanting the eyes
of another Uchiha clan member can the vision be restored, a process that
results in the creation of an Eternal Mangekyō Sharingan.

> **The tighter the blood ties are between the "donor" and the receiver, the
> better it is for compatibility, siblings for example.**

The time from fusing the donor's Mangekyō with the receiver's Mangekyō to the
point of full recovery is at least several days **in the case of Sasuke**.

Not only does this process permanently restore one's eyesight, but it also
gives the person even greater power. The Eternal Mangekyō Sharingan also
changes form from the original, with what appears to be a fusion of the
current owner's Mangekyō with the previous owner's.

Source:-[
**Source**](http://narutofanon.wikia.com/wiki/Eternal_Mangeky%C5%8D_Sharingan)

**EDIT**

For better understanding let me give you an instance. MS happens when a person
kills someone very close to him/her. So the 'tamui' of the Sharingan changes
on its own[ **how tamui changes it's pattern is still not explained** ].

Coming to EMS, a person can achieve it once he **discards his own eyes** and
uses his sibling's ones. That is the mechanism of achieving EMS. Therefore if
the person is closely related to the one who he would take the eye from, then
there is a greater percentage of activating EMS. Hope I have answered your
question now

**IInd EDIT**

Thanks [Krazer](https://anime.stackexchange.com/users/63/krazer) for the
updating the title of the question.From the title,I can come to a conclusion
that no evidence as of now being cited related related to working of sharingan
once it is transplanted.


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After quite some searching I came to the sad conclusion there is barely any
information available on how the 2 eyes get fused. Then again we can make some
educated guesses thanks to some of the shown footage in the anime.

In episode 136 Itachi shows Sasuke how Madara got his Eternal Mangekyou
Sharingan (EMS). Showing the following picture

![EMS Fusion](https://i.stack.imgur.com/dtlvZ.png)

With this image we can deduce that the old eyes are not removed from the body,
meaning there are 2 pairs of eyes in the body from that moment on. The most
plausible reason to pass would be that the 2 eyes fuse in a similar way as to
an artificial limb getting attached to a body. This would also explain the
reason for blood ties as your body might reject people who are not directly
blood linked.

This would also answer your first point, as the eyes fuse it does not matter
whether the begin point was the blind eye or the still functioning eye as they
will become one after all

How do the eyes exactly fuse? and how do they put 2 pairs of eyes in a body to
begin with? Guess this is a sort of anime magic which is not really uncommon
in Naruto to begin with (small sample **(careful contains spoilers if not up
to date with manga)**

> ![Sakura using Medical Ninjutsu on
> Naruto](https://i.stack.imgur.com/czlxd.jpg)


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The eyes are completely swapped. Sasuke even says Itachi's eyes "fit nicely"
at one point in the manga. The transplantee's eyes are removed and replaced
with eyes from the donor. Then some bullshit-no-jutsu happens and the eyes
take on properties of both their original owner and the person they've been
transplanted into. Perhaps because the blood of the recipient flows into the
new eyes causing the DNA to merge or something. But anyways the eyes are
swapped not fused. That's how transplants work. You replace whatever you're
transplanting.


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I think the sharingan transplanted to the new user recognise the bloodties and
therefore grants the new user some new abilities like the perfect Susanoo


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You are all wrong I'm sorry lol the mangekyo awakens a chakra in the brain
after a tragedy or loss of love ect that chakra is transferred to the ocular
receptors from the brain which is why the eyes change shape and color so
therefore when you transfer eyes the new eyes have the old host power engraved
in the and you sharingan is written in your brain so it fuses with new eyes it
was all staed in old Naruto episodes not sure exactly one


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