Well, in some fanfictions, Harry might rely on his other senses more acutely. He could use his sense of hearing to detect movements around him. For example, he might be able to tell if someone is approaching by the sound of their footsteps. His sense of touch could also help him navigate his surroundings, like feeling the walls or furniture to figure out where he is.
In this kind of fanfiction situation, Harry might also have help from his friends. Hermione could use a spell to make his glasses indestructible and then find a way to get the blindfold off him. Ron could use his brute strength to protect Harry while he's in this vulnerable state. They could work together as a team to get Harry out of the situation where he's blindfolded and without his glasses.
One possible consequence is that he might get injured more easily. Without his glasses, his vision is impaired, and being blindfolded makes it even worse. He could trip over things, bump into walls or other objects, and get bruises or cuts.
There could be a fanfiction where Harry discovers the blindfolded glasses in an old, dusty corner of the Room of Requirement. When he puts them on, he's transported into a different dimension within Hogwarts where everything is a mystery. He has to use the limited vision through the glasses (maybe they have some sort of enchanted sight) to figure out how to get back to his own Hogwarts while also uncovering secrets about the castle's past.
Some characters would react with shock. For example, Ginny would be outraged that someone would do such a thing to Harry. She would be ready to fight whoever was responsible. Luna, in her unique way, might see it as an interesting new state for Harry. She could offer some of her strange but useful magical items to help him. And a Hogwarts teacher like McGonagall would be strict about finding out who was behind it. She would also make sure Harry was taken care of, ensuring he had proper assistance in getting around until the situation was resolved.
The plot could be that Voldemort has cursed Harry's glasses to be blindfolded as a way to weaken him. Harry then has to find a way to break the curse. He goes on a journey through the Forbidden Forest, relying on his friends' guidance and his own inner strength. Along the way, he meets magical creatures that offer him clues on how to reverse the curse.
His friends, Hermione and Ron, would surely help. Hermione with her intelligence and Ron with his loyalty.
In a fanfiction, if Harry Potter loses his glasses, the plot will likely take a different turn. His lack of clear vision could make him seem less confident, which would change how others perceive him. Enemies might underestimate him, giving him an opportunity to surprise them. His search for a replacement or a solution to his vision problem could introduce new characters, like an old wizard who specializes in eye - related magic, and new sub - plots could unfold as a result.
One plot idea could be that Harry is blindfolded and without his glasses during a dangerous game at Hogwarts. His friends have to guide him through a series of magical obstacles using only non - visual cues. Another could be that a spell has made him blindfolded and lost his glasses, and he discovers a new magical sense within himself to navigate the wizarding world. Maybe in a situation where he's kidnapped by dark wizards, they take his glasses and blindfold him, but he manages to escape using his other skills and the help of some unexpected magical creatures.
Harry Potter could survive in the dungeon without his glasses by relying on his instincts. He has been in many dangerous situations before and has developed a good sense of danger. He could listen intently for any sounds that might indicate danger or a way out. Additionally, he could try to communicate with magical creatures in the dungeon. Some might be friendly and help him. And if there are any magical objects in the dungeon, he could potentially use them to his advantage. For instance, if there is a magical stone that enhances perception, he could use it to'see' better without his glasses.
One big challenge would be in his studies. Magic often requires precise wand movements and seeing spells being cast by others clearly. Without his glasses, he could misinterpret what a teacher is demonstrating, and this could affect his learning. Moreover, in Quidditch, he would have a hard time seeing the Snitch or other players clearly, which is crucial for the game.
One possibility could be that in this fanfiction, Harry's glasses are some sort of magical anchor. Without them, he might accidentally slip into a different dimension. Maybe he was in the middle of a battle at Hogwarts, his glasses got knocked off, and suddenly he vanished. It could be that the glasses were enchanted by Dumbledore long ago to keep Harry in the 'right' magical space, and without them, he's lost in a sort of limbo.