First of all, I would like to present some information about corneal transplants, which I think may be useful to understand some things. 
Corneal transplant is one of the most frequently performed surgeries worldwide. A cornea transplant is often used to restore vision in a person with a damaged cornea. The corneas used for transplants come from deceased people and everyone can be a universal cornea donor, since, unlike organ transplants, people who need cornea transplants do not require tissue matching. There are usually quite a few cornea donations, so the waiting list is not long. 
The success rate of these operations is quite high (it can be around 90%) and it is a fairly safe surgery, although sometimes complications can occur, such as the development of an eye infection (as happened to Day) or the transplant rejection. Even so, it is the transplant with the lowest rejection rate that exists in the world. If rejection occurs, the person may receive another corneal transplant (so it is entirely possible that Day had two surgeries). Even if the person is not eligible to receive a donor cornea, they can undergo an artificial cornea transplant.

In summary, for Day's corneal injury, there would be a high probability that Day would recover his sight with surgery and that the surgery would occur at some point (in those cases in which the person wanted to undergo it). 

Having said that, let's go to another point. 
All people have their own state of normality, that is, we all have a habitual state. This state can change at some point and varies from one individual to another.
For example, my usual body temperature is 34°, while my father's usual temperature is 36°. If I reached that temperature, I would have a fever, while if my father reached my temperature, he would have hypothermia. Our own state of normality would be altered. Therefore, my own state of normality doesn't have to be the same as another person's state of normality and vice versa. And it doesn't mean that a person's usual state is more normal or more valid than another. Each person has their own. 

As a physiotherapist, I often receive patients in consultation who seek to treat some alteration that they feel has affected their usual state. Within our possibilities and within the capabilities of each person, we try to help patients recover their usual state, their usual functionality, although it is not always possible (but we try to make the person feel the least limited in their day to day). We adapt the therapy to each particular case. 
I am going to pose two situations. 
A woman comes to the clinic with brachial paralysis that occurred at the time of childbirth, due to malpractice. She has her own ranges of motion, which may be different than the ranges of motion that another person has, but those are her normal ranges of motion. In these ranges of motion, she has full functionality and she doesn't feel limited. She goes to the consultation simply to release muscle tension, which causes her discomfort. 
Another woman comes in for a fractured elbow. She tells me that before the injury she could fully extend her elbow, but now she can't. This makes her feel limited in her daily activities, so she asks me to help her regain as much mobility as possible. 
In both cases, each person comes with a different objective, but they are similar in some aspects: both seek what generates greater physical and mental well-being, whether eliminating muscle discomfort or seeking more joint mobility. That is, both seek to feel more comfortable in their own life, with their own body.

In Day's case, he wants to be treated, he wants to recover his pre-injury state, and for his specific injury there is treatment. Is the series ableist for giving Day the possibility of undergoing surgery, when he wants to do so and when in real life, for his specific case, he would have a high chance of having surgery and recovering his sight? It would be unrealistic not to incorporate that possibility, because in real life he has that option (even to receive both surgeries) and he chooses that option as well.

Through the failure of the first surgery, they showed us that Day, although he did not manage to regain his sight, that did not prevent him from continuing to live his life, and in fact, he lived it in a full and happy way. Day assumed that his blindness could become his normal state and that, perhaps, he would not be able to recover his previous state, he adapted to his new reality and continued striving to achieve his maximum potential within his current capabilities and possibilities. For Day, surgery stopped being his priority and he simply dedicated himself to living his life. But, if at some point, the possibility presented itself again, he would take it. He would try it again. And honestly, if the surgery fails again, I am sure that Day would continue living his life, as he did the first time, without feeling limited and he would continue to be happy for everything he has managed to do for himself, for everything he currently has in his life and for all the people he has by his side. 

Restoring Day's sight was the most realistic thing for his case. I don't consider this ableist. The series simply tells us that, within our capabilities and our possibilities, within our own reality and our own circumstances, we can find our well-being and we can reach our potential. It tells us that we must trust in ourselves, in our strength and in our abilities, and that we do not forget to fight for our dreams and our objectives, according to ourselves and not what others want to impose on us. It shows us that although we face difficult situations and moments along the way, although our reality is not always what we would like to live, life will also give us happiness, in one way or another. Each person has their own idea of happiness and any person, regardless of their circumstances, can find that dose of happiness in every moment of their life, in the things we do in our daily lives, in the things we achieve with our effort and in the people we love. All people can and deserve to have a happy life, a full life and a life in which they feel as comfortable as possible, surrounded by people who love them and accept them for who they are. This is what the series has conveyed to me. 

And also, personally, I feel that Day's words have been taken a little out of context, although I recognize that perhaps they should have expressed it differently to avoid the misunderstandings that have occurred. I already talked about it in the review, but for me his dialogue refers to his life at the beginning, when he locked himself in his room, totally depressed, refusing to live his life, simply waiting for that surgery to come. Until Mhok came and made him realize that he could live his life the same way as everyone else, that he could live a normal life even if he couldn't see. Day talks about the difficulties and painful moments he faced throughout the process, but in the end, when he was able to accept his new reality and adapt to it, he began to see the light, he enjoyed life again and he achieved his personal and professional development, like anyone else would. He no longer wanted to be locked in his little corner, being a statue, he wanted to be part of the world. In the end, for him, recovering his sight was no longer a priority, simply another possibility.

Thank you so much for this! Hopefully, people can now understand this show a bit more and even learn new things along the way. I love how you did your research and also showed us some examples to help us understand Day’s situation a bit better :)

 Kreep:

Thank you so much for this! Hopefully, people can now understand this show a bit more and even learn new things along the way. I love how you did your research and also showed us some examples to help us understand Day’s situation a bit better :)

Thank you for reading. I just wanted to capture what the series has conveyed to me. I liked the ending, I didn't think it was as bad as so many people have commented. I also haven't felt that the ending ruins anything or that it contradicts what was shown previously. But each person has their own perspective, that's how it is.

THANK YOU FOR THIS!! 

I completely agree with everything you said! I don't know where people got the idea that corneal transplant was so rare that it was so unrealistic for Day to have the surgery twice and for it to be successful. And I also don't know where people got the idea that given the chance to regain his sight Day should have rejected it because he has to be some kind of hero, when in real life no one would reject this chance. 

I also think Day's words at the end were taken out of context, mainly because people were waiting for a "GOTCHA!" moment from the series and call it ableist. I agree that maybe the translation could have been different to avoid misunderstandings, but to me it was very clear that what Day refers to as the worst moment of his life and a dilemma was the time right after the accident. He was literally miserable for a whole year, and he even said that he was like Mee, he made himself invisible and let the world forget him. Besides that he was so angry with his beloved brother and I'm sure that also made him  so miserable. Then as he said at the mountain and as you said, he saw the light, the hope, when Mhok entered his life and showed him that he was no different from anyone else, that he could still do a lot of things and that his friends still loved him and just wanted the best for him. 

Lastly, you are completely right, the ending doesn't erase anything from the series! Day gaining his sight back doesn't change the process of acceptance he went through nor everything he learned about life, hope and himself during that time. He was blind for about five years (the first year before knowing Mhok, the time from ep 1 to 11 it's about a year and then the 3 years time skip) and he learned so much and got to be so happy with his life and himself.

So yeah, they could have done some things differently and the ending did feel rushed, but overall it was good and doesn't take anything away from the series and the message they tried to convey, which from the start was hope (according to P'Aof on Before Last Twilight).

Thank you very much for reading and thank you very much for sharing your impressions about the ending. I totally agree with you. Furthermore, after all the effort that the team has made to show us that disability is not an impediment to leading a normal, full and happy life, I don't know how people could think that in the last minutes of the finale they were going to say the opposite and to destroy all the work. If for the people who have seen the series that wouldn't make any sense, then for all the people who have worked on this series for so many months, it wouldn't make any sense either. They have worked very hard to bring us this story and they have done things well throughout the series, so I think they at least deserve a little trust from the viewer. It seems a little unfair to me that people assume that they don't know what they're doing and that they've ruined the message, when that's not really the case. Anyway, even though everything is there for the viewer to understand, they still should have expressed things differently to avoid misunderstandings. But I also believe that translations do not always fully capture the essence of the original language, since there are words or expressions for which there is no exact translation in another language and it must be adapted. This also causes the original meaning to be lost and this can lead to things being understood differently than intended. But this is just my opinion. Obviously each person will see it differently.

Adding to what you said about the people that made this story, they did their research. The writer mentioned how he asked some visually impaired friends of his about their experiences and they even had a visually impaired coach to help Sea understand Day better. It's not like they made the ending from a place of ignorance, they researched and talked with people who experienced this before so that they could make the best decision for the ending. 

That's correct, language doesn't always translate perfectly. My first language is not english so I'm always struggling to find ways to say things that I normally say in spanish but there is no direct translation in english a lot is lost in translation, so we can't always judge something by the way it is translated because it won't always be correct or the best translation.

That's right! They have researched, they have received advice and they have taken into account the experiences of people with visual impairments. They know their characters and their story in depth, which is why they have chosen the ending that they considered most coherent and appropriate to what they were telling.

I totally agree with you. In my case, Spanish is also my native language, so I understand how difficult it is to express yourself in another language and to find the right words for what you want to convey.

Maybe I'm too late for this to comment but finally someone has spoken clearly and I want to thank you for this. When I finished this series first, I was completely captured until it ends. Then I started watching some reactions from different social sites and got their opinions. Most of them sided on Day's not getting his vision back to make the series have more impact especially for blind people and inability to see is not hindrance to continue and have happy life. I even debated on their comment section and pushed my limit to express my thoughts.  I tried to survey some blind people I know and they have similar response (undergo eye surgery) and based on this, the ending was most realistic. Take note also, Day come from a rich family. 

 Toki:

Maybe I'm too late for this to comment but finally someone has spoken clearly and I want to thank you for this. When I finished this series first, I was completely captured until it ends. Then I started watching some reactions from different social sites and got their opinions. Most of them sided on Day's not getting his vision back to make the series have more impact especially for blind people and inability to see is not hindrance to continue and have happy life. I even debated on their comment section and pushed my limit to express my thoughts.  I tried to survey some blind people I know and they have similar response (undergo eye surgery) and based on this, the ending was most realistic. Take note also, Day come from a rich family. 

Thank you very much for reading it and for taking the time to comment. It's a shame this series was judged so harshly. I think they have made a good representation and they have shown a lot of sensitivity in this regard.