Checked by retina specialist, no vitrious detached or pvd, vision 6/6 every thing normal, then why i got floaters, what may be the reason? i am 23.

Debris in vitreous: Floaters are any debris or discontinuity in the cavity of the vitreous. Most first show up in older age but a few have them scattered in the vitreous even at a young age. As long as there are few and the vision is unchanged, consider them an annoying but not dangerous issue. You have consulted a retinal specialist who found nothing to worry about - that was the right thing to do.

Degenerative floater: Degenerative floaters are caused by vitreous changes with age/time, which can start at a young age, esp. if the eye is nearsighted. If there are sudden new floaters noticed under less light intensive circumstances, they might signal a retinal tear, and an eye exam is highly recommended -but in this case was already normal.