Honestly, I don't believe in love at first sight, so I'm definitely biased there. But I do believe in true love... Here's how I see it, two people see each other, and become infatuated with each other. They like the way the look, or like their mental assessment of the other person... Because total strangers really know nothing about each other, I don't believe they can be in 'true love' at first sight. I think of true love as an elderly couple, who's eyes shine when they look at each other. I've met some people like this, and when I come into the room I can just see how the love is shining out of their faces.... anyway.... (br/)
I believe true love is something that people have to work at over the years. I don't think it just happens instantaneously. Even those old couples had arguments with each other, and got better at understanding each other with time... It just doesn't make sense to me that two complete strangers could fall as deeply in love as those older folks are at first sight... but, I suppose it's always possible... and by no means take my answer as the only right one! I think this is largely a matter of opinion.... and, well, that was mine.
The answer mostly depends on you own definition of true love. In my opinion, yes it does exist but it can take a long time and hard work to achieve it. I know people who would risk their lives for their significant other and I also know people who accept their spouse's worst flaws that no one else does.
When you say 'at first sight' i'm assuming you means that the two people don't know much about each other. At most, love at first sight can be physical attraction. The physical attraction can be cause by the person's beauty, attitude or how they carry themselves but it cannot be called love. It's simply attraction.
Yes, I believe true love exists. But I don't believe in the notion that everything is perfect and it all suddenly falls into place. Love is hard work. It takes putting someone else's needs before your own. It needs communication and trust. All these things are developed over years, where doubt and mistakes and boredom are all things you need to face the longer you are with someone. But if you truly love a person you can overcome those things together, no matter how difficult it gets.
Love at first sight, however, I think is just nonsense. Lust and infatuation, sure, that can happen the first time you see someone. But love takes trust and time to develop. It's not something that can happen right away, imo.