I don't understand. Did you go get an eye checkup for this specific issue or for something else? Why didn't you ask your eye doctor this? Do you wear glasses or contacts or something, so only were getting a check-up from an optometrist? Did they say they couldn't answer your question? And if not, did they say to go see another specialist, perhaps an MD or specific MD specialist, like an ophthalmologist?
I don't know why you would assume anybody on here would otherwise know more than your own eye doctor, but most common cause is due to age related eye changes, which I assume wouldn't apply to you, if only 14, so probably should go back to your eye doctor if didn't ask them at your checkup, and if you did ask your eye doctor, and they said you needed to see another type of specialist, then make an appointment to see somebody else in that specialty, which if your eye doctor was an optometrist, they may have just said you should see an MD, i.e., medical doctor (because optometrists are not MDs). As if it was just an optometrist, the other causes wouldn't likely be able to be treated by an optometrist, as it would probably require further diagnostic testing they don't usually perform, and/or need prescriptions outside their board license to prescribe, as it could be due to certain eye infections, or auto-immune problems causing inflammation in the retina, or some condition causing more vitreous fluid to expel from retinal tissue, or due to some other underlying conditions, that either your family medical doctor or ophthalmologist should address.