While looking through CoS today I found this:

Whoa. Nice find. Perhaps he had already gone under one magical transformation before he turned 16? We know that he became obsessed with the dark arts early on in his life. But at age 16 already... I don't know what to think.

It might have more to do with his 'solidness' than his dark magic at that time. I'm positive that he has preform Dark Magic by age 16 but enough to start giving him his signature red eyes? It might have to do with the power transferring from Ginny to him making him stronger than he was at 16 and making him more like his present (more powerful) self (Voldemort).

I have a feeling that the red gleam was from either...

1. The Diary
2. Allergies
3. The lighting in the Chamber

The diary because it is probably made of Dark Magic. I think Tom began to turn into Voldemort when he first opened the Chamber of Secrets. Since Voldemort is filled to the brim with the Dark Arts, his eyes are red because of the tranformations and/or a side effect. Got to be careful about those potions/spells/other oddities these days - you never know what they put in 'em! Anyway, since Tom just began to transform into Voldemort, the Dark Arts are only just beginning to take affect, thus he only having a gleam of red in his eyes.

As for the allergies bit, if you ever known someone with allergies, you know their eyes can get red. Now, while it may of appeared to be a "gleam" to Harry, it might of actually been a full on dust allergy attack to Tom. So, Tom, being the smart boy that he is, performs a spell (without Harry knowing, of course) that stops his eyes turning red for the moment. (However, because there is so much dust in the Chamber of Secrets - it hasn't been in usage for over fifty years, there is bound to be dust - Tom's eyes continue to "gleam" red. Actually, it could be any allergy, but we'll say that Tom is allergic to dust. )

And for the lighting in the chamber, I have brown eyes. Lit in certain ways, they can appear to be gleaming red . It could be the same with Tom. If he has brown eyes, that is.

So, that's that!

Wonderful topic, Mrs Brisbee!

His eyes gleaming red IMO are a sign of the dark magic being imposed on Ginny: draining life force.
Voldemort's eyes as an adult are from his serpentine nature, which correlates with the consumption of other lives to perpetuate his own.

very good observant!
probably dark magic made his eyes voldemort red!
you know, voldemort's powerful making him one of the darkest and strongest wizards!

Very interesting topic... I think that the red gleam may have had something to do with creating horcruxes. According to DD in HBP, the diary was the first horcrux Riddle made... so perhaps the more horcruxes you make, the redder and more gleaming the dark wizard's eyes become. So if Riddle had only created the one horcrux by the time he completed work on the diary, that would mean his eyes would only be a little red... and by the time Harry meets him in GoF, he has glowing red eyes.
... just a theory.

I wonder if the eye color thing will come back in book 7... I'm pretty sure there is a thread about this in the pre-book 7 area. It's more related to the importance of Harry's eyes being green though because of something Jo said in an interview about it.

Sometimes when i write a story, which i often like to do, and every wirter does it, is describe things. So maybe the eyes have nothing to do with anything. It could just symbloise that Tom is evil. becasue isnt it at that time TR hasnt told Harry he is LV. Just today i wrote a story about a woman who had a glint of hope in her eyes...i dont know whther or not its right or if its importan.t But good thinking!!

I think it is possible that he is already evil...Yes, it is likely since you know he was the young Voldemort. Was he not?

I don't think there was any special reason the 'red glint' was used to describe him. A lot of things like that are literary devices that help the reader get a sense for the character. Because of the gleam, it made of us go, "WHOA... This dude's a little bit evil..."
At that point, I think it's crossing Harry's mind that this Tom Riddle isn't as good as he thought him to be, and because of the description, us readers caught that too.

I'd have to agree with Fenixong...at that point in time Tom Riddle had already killed once hence how he made the Horcrux out of the Diary. He had killed his father and grandparents using his uncle Morfin's wand. He was already becoming less and less himself. By the time Harry meets him in GoF he has already killed many times so his eyes would then be glowing red...i dunno maybe the deeper Voldy sank into his evil thoughts and ways the redder his eyes get?

I agree that is something weird and easy to overlook. That’s why so many people think that he’s an animagus because of that. Hmmm maybe it has something to do with why Harry’s eyes are green like his mothers. Warm color against a cool color. Hmmmm interesting.

I just have to take a guess here. I think the gleam was just there because he was mad that Harry escaped and that he was very badly hurt. He always has red eyes, doesn't he? He was probably just happy that he had Harry alone in the Chamber and he could kill him(I think he could, but I'm not completely sure. Maybe he can't because he's just a horcrux.)

Have you ever heard of a person that always has red eyes? Creepy. Nah, he has that odd gleam when he has an excess of feeling.

I believe that what Tuitus is tryling to say is that Why would Tom Riddle have that gleam so early?

I now believe its because the horcrux was made AFTER this point in time.

It says in HBP that he got a red-gleam in his eye when he was mad and really wanted something.. In a memory where the chick showed Voldy the cup and the locket his eyes gleamed red and she was like are you okay? and they went back to normal and he said yeah, and she said.. it must have been the light... and it also says it in the horcrux memory of slughorns... the Real one.. they go red before he says wouldnt 7 horcrux's be the most powerful..

I think they go red when he really wants something..
ex - The Cup/Locket - Information - and In The Original Topic Quote maybe to kill harry? -

Trying to remember back to the sixth book, but if my timeline is correct, hadn't he already murdered his uncle dude (Gaunt) by then? Cause he had by the time he was wanting to even make the Horcruxs; he had the ring. So he must have killed someone already, and thus he used the diary at the end of his 6th year (or in the middle, though the end would make the most sense, cause he's moving on, and all that jazz, and yeah...), which I think was his first horcrux, if I'm right. Then he murders the Riddle family, and is there another horcrux in there? I really need to write out this time line, I've used it twice recently and was probably wrong on both accounts.

Anyways, getting back to my main point, we know he's already murdered some peeps by then, so his soul is already getting mutilated... Wow, I just had an awesome Horcrux moment about souls and respect for life. Anyways, returning to this. His soul is all mumbo jumbo, and so it sounds like he's taking some steps to immortality already. So I wouldn't be surprised if there were already some changes, here and there. Not like the nose thing, but I can bet he's like paler, or something. Cause splitting of ones soul can't go unnoticed, which totally brings up something not to be talked about here, jakin...

The last thing I want to say is that it's also a stylistic choice. If we know the red is there full on later, than by having a slight bit of a gleam now, it really shows what he is. It can also show how far along he is down the path, that he's already murdering, and splitting his soul, and pretty much making Dumbledore want to punch him in the face. Hey, he's still got his nose, that's fine by me.

~Aeryn~

For a guy who has torn his soul apart, I wouldn't put it past him to have a red gleam to his eyes. I mean come on, if he can separate his soul, he's bound to be pretty different that most people.

I think him having red in his eyes was mostly just so the reader could more vividly imagine what LV looked like. The red eyes just say, this guy isn't just evil, he's beyond evil. Not to mention in the second book we didn't really know much about LV's past at all, except that he was Tom Riddle.

Maybe the "red gleam" was more like the one we see in flash pictures (red-eye) or the way animals look when you shine a bright light in their face?

Dumbledore made a comment once about Voldemort becoming less human as the years went by. So by extension, was he becoming more of a savage, something bestial with eyes that glowed in the dark?

I think that his eyes had a red gleam because he had already made a Horcrux by the time he was 16. Riddle said in CoS that he opened the chamber in his fifth yea. It resulted in the death of Moaning Myrtle and the creation of the diary Horcrux.

the gleam was the gleam voldemort always has when someone mentions mighty power and the Darkest dark arts. That gleam eventually takes over his entire eyes when he gets back his body. Since at 16 he was already after horcruxes he would have already been into power and the gleam would have been present.

I agree that the gleam was from the fact that his soul had already been mutilated by at least one horcrux at this point. Also, lets not forget that the Tom Riddle we see coming out of the diary is one eighth of Voldemorts soul. So, as Voldemorts eyes become more red as he becomes less human the pieces of his soul inside his horcruxes would certainly be less human, and they would have that red gleam. Also, I think it was also just a little bit of writers touch to make the scene a little more intimidating

Some people are saying are saying it's because he has already had his soul ripped in two from killing. But almost all of his Death Eaters have killed haven't they? Almost all of them have had their soul ripped apart. After all, it's the killing that rips the soul in half, rather than the Horcrux making. How many of them do you see walking around with red eyes. None. No, I think it is because Tom Riddle always had the Voldemort in him somewhere, and at moments of high emotion e.g when he wants the cup, or when he is near to killing Harry, the Voldemort within him came to the forefront, giving his eyes a red gleam, characteristic of the fully formed Voldemort. Eventually as time goes by Tom Riddle turns from the good looking, clever prefect to the Dark Lord as the Voldemort inside him steadily takes over. Eventually we see him fully consumed by the Voldemort within him, and he becomes the Dark Lord. But there is evidence that the Voldemort within is slowly growing - the occasional red eyes, the cheeks becoming more hollow, his complexion becoming paler. I think the Voldemort within slowly takes over.
Be interested to know what you think about this theory.