Rebbi Aba sent to Rav Yosef a ruling that one who was able to testify about the boundaries of a tract of land for someone else but then he became blind may not testify, even though he can still describe the boundaries. The Gemara then cites the opinion of Shmuel who argues and says that a blind person may testify since he can describe the boundaries, but he may not testify about an cloak. Rav Sheshes argues and says that he may testify about a cloak by describing its measurements, but he may not testify about a slab of silver. Rav Papa says that he may even testify about a slab of silver, since he is able to describe its weight.
The Gemara then cites a Beraisa which teaches a general principle -- if the witness is not a valid witness from beginning to end, then he may not testify. The Gemara says that this Beraisa refutes "all of them," and the Rashbam (beginning of 128b) says that it refutes Shmuel, Rav Sheshes, and Rav Papa, implying that it does not refute Rebbi Aba. The reason it does not refute Rebbi Aba is because he says that a witness who became blind is indeed Pasul, like the Beraisa says.
My question is that Rebbi Aba was only referring to giving testimony about land , as he specifically mentioned. Perhaps he agrees that one who became blind may give testimony about the other objects mentioned, or at least about an event that occurred, such as a Halva'ah! Thus, it would seem that the Beraisa is also refuting Rebbi Aba.
The YAD RAMAH says that Rebbi Aba certainly would invalidate a witness who became blind from testifying about Metaltelin. Rebbi Aba here is saying that such a witness may not even testify about the borders of land (which is less subject to error). Hence, his view is consistent with that of the Beraisa.
The Yad Ramah seems to be learning that when Rebbi Aba invalidates a witness who became blind, it is because he holds that being blind is an intrinsic Pesul in a witness, and not merely that a blind person cannot know the details of boundaries well.
It is still not clear how the Yad Ramah knows that Rebbi Aba holds that being blind is an intrinsic Pesul that invalidates the witness from all forms of testimony, especially since Rebbi Aba did not say a general rule but rather he ruled in a specific case (that of Edus Karka).
I found that the HAGAHOS CHAVOS YA'IR on the Rif (57a of the pages of the Rif, #3) suggests also like the Yad Ramah, that Rebbi Aba would say the same thing regarding testimony about Metaltelin. However, the Chavos Ya'ir says that this is "Tzarich Iyun," because from the words of Shmuel, Rav Sheshes, and Rav Papa, it seems that they are addressing specifically Rebbi Aba's case of Karka, and that Rebbi Aba himself was not discussing Edus for Metaltelin at all.
The ROSH (8:24), though, says that Rebbi Aba holds that a witness who became blind is Pasul for all Eduyos, Karka, Metaltelin, and Halva'ah, because being blind is an intrinsic Pesul (and the fact that he knows the information that he is testifying does not matter), like the Yad Ramah implies. The Rosh says that the reason why Rebbi Aba specifically mentions Karka is because he is referring to Shmuel's ruling, wherein Shmuel permits a person who became blind to testify about the boundaries of land. (The Chavos Ya'ir says that this explanation is a "Dochek Gadol," because Rebbi Aba was sending a ruling to Rav Yosef bar Chama and he was not responding to Shmuel's statement.)