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.
He would probably be very disoriented. Without his glasses, Harry's vision is extremely poor. In the dungeon, which is likely to be dark and full of various obstacles, he might stumble around, bump into things, and have a hard time finding his way out. This could lead to some dangerous situations as he may accidentally trigger traps or run into unfriendly creatures.
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.
His relationships might change. Some of his friends might not recognize him at first without his glasses. This could lead to some initial awkwardness but also force him to re - establish his connections in a new way. He might also attract new attention from characters who were not interested in him before, either romantically or as potential allies or enemies. This new social dynamic could cause him to grow as a character and develop different aspects of his personality.
Harry might initially be in a state of shock. He has always been able to rely on his glasses to see, and without them, the world is a blur while he's being tortured. This could make him angry too. He might lash out blindly, trying to cast spells in the direction he thinks his enemies are, even if he's not sure. And as the torture continues, he could become more determined to resist, using his strong willpower to endure the pain and fight back in whatever way he can.
He might be very frustrated. Without his glasses, he can't see well, which is a big handicap for him. He could be trying to use his other senses more acutely, like listening for any approaching footsteps or voices. He might also be thinking of ways to break free from the bindings using some basic spells he can do without clear vision, like a simple levitation charm to try and reach for his glasses if they're nearby.
His relationship with Hermione might change. Hermione would probably be more protective and try to help him find a solution to his 'without glasses disorder'. She might also be a bit more bossy as she tries to guide him around since he can't see well.
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.
A fanfiction like this could explore Harry's character in a new light. Usually, his glasses are a part of his iconic look. Without them, he's not only physically different but also psychologically. He might feel more exposed and less confident. This could change how he approaches situations with the Snatchers. For instance, he might be more hesitant in making decisions or using magic, which could have a big impact on the outcome of any encounters.
When Harry stumbles without his glasses, it could initially disrupt his magical abilities. He may fumble with his wand or mispronounce spells because he's distracted by his lack of clear vision. However, over time, this could force him to become more adaptable. He might learn to use magic in new ways, like using magic to enhance his vision temporarily or using spells that don't require precise aiming. This would make him a more versatile wizard in the long run.
In fanfiction, without his glasses, Harry Potter might be seen as more vulnerable. His glasses are like a part of his identity, and without them, he may struggle more with seeing clearly, which could add an interesting layer to his character, like when he's in a dangerous situation and his blurry vision could lead to some unexpected plot twists.