If there are white spots in the dark part of the eye, or a lot of tears in the eye, and they are permanent, then the Bechor (firstborn animal) is considered disqualified. Both of these things—white spots in the dark part of the eye and a lot of tears—will eventually cause the animal to go blind. Even though it is not blind right now, its eyesight has diminished, and therefore it is disqualified.
What is considered permanent white spots that would disqualify the Bechor? Any white spots that are in the eye for 80 days. If they stay there for 80 days, then they are considered permanent. If they are there for less than 80 days, they are temporary, and the Bechor remains valid. It is not enough to check only on the first day and the 80th day, assuming that the spots had the same status during the 80 days in between. A person needs to check three times within those 80 days to know that the white spots were there the entire time. That means someone should check every 27 days to know that the spots were there throughout, rather than making assumptions about their status between checks.
What is considered permanent tearing in the eye? The animal has to be tested in the following way, which is a little more complex than the white spot test we just mentioned. You have to feed it moist food and then dry food from a rain-watered field. The test is done from the beginning of Adar through the first half of Nisan. You have to feed the animal grain from a field growing at that time that was watered by rain, as opposed to irrigation. Afterwards, you have to wait until after the summer, from the beginning, or the time, of Elul through the first half of Tishrei. That is considered to be the dry season, as opposed to the rainy season of Adar to Nisan. Then you also have to feed the animal food that grew during that time, again from a rain-watered field.
This procedure—first feeding it food from the Adar-Nisan time, from a field watered by rain, and then again, months later, food from a field that was also rain-watered as opposed to irrigated—would in many instances heal the problem of an animal that was tearing too much. But if you did not follow that order, or did something else—if you fed the animal moist food and then dry food from an irrigated field instead of a rain-watered field; if it ate the dry food, meaning the food of Elul and Tishrei, and then afterwards the moist food of Adar-Nisan, instead of eating the moist food first—it is not considered a permanent blemish. You first have the moist food, and then the dry food afterwards. There is a certain seder (order) that has to be followed in what the animal eats in order to say, “The medicine didn’t work. The blemish is still there.” At that point, you can consider it a permanent blemish, and the person would be allowed to eat it, to do Shechita (ritual slaughter), and does not have to bring it to the Beit HaMikdash as a korban (offering), as a bechor.