In describing Yaakov's preparations to bless his grandsons, Ephraim and Menasheh, the Torah informs us "ועיני ישראל כבדו מזקן לא יוכל לראות", indicating that Yaakov couldn't see well (בראשית מ"ח:י). Interestingly, both Yaakov and his father Yitzchak,as an apparent result of their blindness, reversed the status of a younger and an older descendant in blessing them.
The Gemara in Yoma (דף כ"ח:) emphasizes that our Avos fulfilled not only all of the Mitzvos of the written Torah, but even those of the Torah Sheb'al Peh. The Mishneh Lamelech in his commentary on the Torah called Parashas Derachim, seriously entertains the possibility that when our Avos accepted the Mitzvos, they elevated their Halachic status from that of Bnei Noach before Mattan Torah to that of full-fledged Jews. Even though, for example, the Gemara in Sanhedrin (דף נ"ח:) states that a non-Jew can be punished by death for observing Shabbos, reclassifying our Avos as full-fledged Jews, would allow us to say that they were indeed fully Shomer Shabbos.
The Halachic status of Yaakov Avinu, at this stage of his life, and subsequently of all blind Jews, has been discussed in great detail. The Gemara in Bava Kamma (דף פ"ו:) quotes Rabbi Yehudah who exempts a אמוס, a blind person, from various laws. According to the statement on the next page (שם דף פ"ז.), Rabbi Yehudah exempts a blind person from all the Mitzvos of the Torah. Initially, Rav Yosef, who was himself blind, commented that if someone would tell him that the Halacha follows Rabbi Yehudah, he would make a festive meal for the rabbis because he would be delighted that although he is not obligated, he still performs the Mitzvos. However, Rav Yosef continued, once he heard the statement of Rabbi Chanina that the reward for those who are commanded is greater than that for those who aren't commanded, he would make a festive meal for the rabbis if someone
were to inform him that the Halacha does not follow Rabbi Yehudah.
It is interesting to note, moreover, the dispute between the Tanna Kamma and Rabbi Yehudah in the Gemara in Megillah (דף כ"ד.). In contrast to a קטן who is prohibited to serve as the Sheliach Tzibbur and to publicly recite the Beracha of יוצר המאורות, the Tanna Kamma permits a blind man, a אמוס, to serve in that capacity. However, Rabbi Yehudah disagrees and argues that a אמוס is not obligated to say the Beracha of יוצר המאורות since he cannot derive pleasure from the creation of light. He therefore cannot be the Sheliach Tzibbur. Tosafos (שם בד"ה מי) points out that if the blind man could enjoy the benifits of light , even Rabbi Yehudah would require him to recite the Beracha. In order to reconcile this point with Rabbi Yehudah's statement in Bava Kamma exempting a אמוס from all Mitzvos, Tosafos suggests a simple solution. On a Torah level, Rabbi Yehudah exempts a אמוס from all Mitzvos, but מדרבנן he is obligated to fulfill many commandments so that he will not become like a non-Jew and will be involved in spiritual pursuits.
The Shulchan Aruch (אורח חיים סימן נ"ג סעיף י"ד) accepts the view of the Tanna Kamma in Megillah, allowing a blind man to serve as the Sheliach Tzibbur, even to recite יוצר המאורות. The blind man, it is explained, does benifit indirectly from the light which enables his friends to assist him. The Rambam too (פרק ח' מהלכות תפלה) states that the law does not follow Rabbi Yehudah. In addition, the Rosh (שו"ת הרא"ש כלל ד') writes that a אמוס is obligated in all Mitzvos, and consequently may be a Sheliach for a fellow Jew. The Pri Chodosh (או"ח שם ס"ק י"ד), however, quotes the opinion of Rabbeinu Yerucham that the law does follow Rabbi Yehudah, and a אמוס is thus not eligible to be a Sheliach Tzibbur. However, the Pri Chodosh emphatically argues and says that we must follow the decision of the Shulchan Aruch and the other Poskim who accept the view of the Tanna Kamma that a אמוס is obligated in all Mitzvos of the Torah.
The Shulchan Aruch (או"ח סימן קל"ט סעיף ג') writes that a אמוס cannot be called to read from the Torah since the written Torah cannot be recited by heart. The Ramo, however, states that nowadays a אמוס is not any different than an ignorant person, who may not know how to read at all, but may still be called for an Aliyah. Since we have an appointed בעל קורא (replacing the original system, in which the עולה himself read his Aliyah from the Torah), a אמוס is allowed to receive an Aliyah and recite the Berachos by heart.
Regarding Havdalah, the Shulchan Aruch (או"ח סעיף רצ"ח סעיף י"ג) comments that a סומא cannot make the Berachah on the candle. The Magen Avraham (שם ס"ק י"ז) notes that this limitation is based upon his inability to derive direct pleasure from the glow of the candle. However, he argues that the אמוס is responsible to recite the other Berachos of Havdalah.
The Maharshal (שו"ת מהרש"ל סימן ע"ז) records the responsibility of the אמוס to recite Kiddush Levanah. In contrast to the Berachah on the Havdalah candle, the blessing on the new moon doesn't represent an individual's sense of pleasure, but rather a communal level of enjoyment. We, as a nation, are thanking Hashem for the creation and the continuous appearance of the moon and all of the heavenly bodies. We can now similarly conclude that the אמוס can be the Sheliach Tzibbur even for the Beracha of יוצר המאורות in order to express Klal Yisrael's gratitude to Hashem for His magnificent creations.