Ginny always knew there was something wrong with her eyes. Ever since she was young she worried about what would happen when her eyes finally stopped working. She had almost grown used to the odd flashes when everything she saw suddenly went to black and white. Or when she could only see things out of her peripheral vision.
Her mother had always passed the problems off as either a bump on the head that would go away soon enough, or too much time playing with Fred and George. The curse of an active childhood with many equally active older brothers, Ginny supposed, was that minor scrapes and more serious scrapes tended to be lumped together and that all of it could be healed with a kiss.
Tom Riddle had laughed at her description of her vision problems, telling her that there was no cure. She had been born with a birth defect and magic could only cure things that happened to the body after birth. She had took him at his word; why would he bother to lie about that?; and never bothered to go to Madam Pomfrey for help. Further exploration in the library proved that Riddle hadn't been lying about this and Ginny began to wonder what else he hadn't lied about only to have those truths buried underneath Gryffindor obstinacy.
The symptoms came and went at their own whims, but Ginny knew that someday her vision would abandon her completely. With that in mind she practiced not seeing. She put a blindness spell on herself for two weeks once, and learned how to use other senses besides sight, touch and hearing mostly, to get around.
She also learned that her magic could be used as another sense. Being blinded gave Ginny a better sense of what was inside of her, rather than what was around her, and through that she discovered that her magic wasn't constrained by silly things like spells and wand movement. It was a deep pool that existed inside of every being. The magic inside of humans could be molded and directed to a specific use. Wands and spells gave wizards and witches the ability to concentrate those powers into a weaker, more malleable stream.
Inside of Ginny was a magic pool that she could wield as she wished, now that she knew it was there. She could create much more powerful spells without the use of her wand, if she wished, but she could also send her magic outside of her body to come in contact with everything around her.
Everything, from a human to a chair to the pebble in her shoe, had magic flowing inside of it. When Ginny's magic encountered these other magics she received a picture in her head of these pools of magic and the general shape they took. After three years of practicing with this form of magic she knew that everything had a flavor to their magic, something that could distinguish one pool of magic from another's.
Each human's flavor was specific to that human. From Ron she felt recklessness, temper, love, and a myriad of other little things that set him apart from Harry's flavor of bravery, ambition, and responsibility, or Hermione's learning, intelligence, and friendship.
Ginny mastered the use of her magic as quickly as she could. She could walk around a chair and know if it was an armchair or a desk chair and know who was sitting in it and what they were doing at the time. She could cast spells without a wand, words, or hand motions and they were more powerful than anything she could have done with her wand. Sometimes this magic sense was even stronger than regular sight because now she knew whenever a Slytherin with bad intentions was lurking behind a blind corner, waiting to harass her.
In fact, the only thing she couldn't do with her magic was read. She could hold a book and know that it was a book that contained spells versus histories, but she couldn't read what was written inside.
As her wonky vision grew worse, the most recent of which had been large black spots dancing across her eyes, she took her schoolbooks and papers to an abandoned classroom down an equally abandoned hallway and put spells on the books to read themselves aloud and spells on her quills to write what she dictated. It wasn't easy, but it got her homework done in the end.
Her vision finally went for good in the middle of her fifth year. Christmas break had ended and she had returned to school with everyone else. Ginny remembered the brilliant scarlet hangings around her bed as she went to sleep that night. When she woke up her eyes only saw blackness.
No mater how many spells she tried or how many times she rubbed her eyes hopelessly, the colors never rose back to the surface, the light never shone inside her eyes. She cried then, at the futility of trying to bring back something that was permanently gone. She had arranged for this, studied and practiced, but nothing could have prepared Ginny for the desolation losing her sight instilled inside her.
She would have cried for a week straight if it hadn't been for her clock chirping out, "you're late!", in a voice fairly reminiscent of Molly Weasley's. Ginny jumped to her feet and smiled as her magic immediately snapped into place. She could still see, just not in the conventional sense. She would muddle through somehow.
She expected everyone to notice at breakfast that morning, as if there was a giant sign above her head that glittered and shone, telling the whole world that she was blind. But there was the half-blood prince to worry about, and apparition lessons, and what Draco Malfoy was up to, and Voldemort, and school work, and so many other things that no one had the time to specifically look at Ginny to see that something might be different.
She wasn't running into things or screaming hysterically, as a newly blinded person might. Instead she sure-footedly made her way over to the Gryffindor table, said her usual hello's and ate her breakfast, exactly as she had done every day previous for the last five years.
The year progressed. Ginny got her OWL's completed with a discrete spell that read the test questions aloud specifically to a small piece of cotton stuffed in her ear, and suddenly Ron was running by, shoving Felix Felicis into her hands, and babbling about Malfoy and the Dark Mark.
Death Eaters were everywhere; Ginny could feel them by the sheer malevolence their magic exuded. She fought them with everything she had. The Felix Felicis wasn't lucky enough to bring her sight back, but she didn't need sight to stop a couple of Death Eaters from killing everyone around her.
Every Death Eater that saw her face that night knew there was something different about her, but before they could figure out what, she had disabled them and moved on to her next prey.
Then she heard yelling so she turned to see if there was something she could do.
Color returned in a bright flash that almost blinded her worse than being blind was. She nearly clapped a hand to her eyes but stopped at the last minute just so she could see what red looked like again, or green as Draco Malfoy rushed by, followed by Snape and, distantly, Harry.
Then Malfoy was past her and gone down the hallway and the color vanished again.