I suddenly need glasses- why?

A few months ago I realised that my eye sight had deteriorated and things that were far away were blurry. Before this I had perfect vision.

So I went to the optician and I now have a prescription of -0.50. I know this isn’t much but I genuinely struggle to see properly without the glasses.

I tried to google to find out why the sudden change in my eyes but everything comes up with age deterioration, entailing 40+ years.

I am only 19 years old and I’m struggling to understand why the sudden change. I’m also quite worried. Apart from the sight, I was told my eyes are healthy but could I have a medical condition or is it still normal for ur eyes to change as a teen naturally?

-0.50 is nothing at all, so don't worry about that. It's relatively common for young adults to start needing glasses and if your opticians was worried about anything, they would have sent you to your GP or an ophthalmologist to get you properly checked out. So don't worry about it

it can be genetic or from a growth spurt... my dad got glasses as a teen, me and my siblings got glasses under the age of 9 🤷*♀️

And u guys could see perfectly fine before needing glasses?

And u guys could see perfectly fine before needing glasses?

And u guys could see perfectly fine before needing glasses?

It can seem 'sudden' because you've got to a point where you can't physically compensate any more for your vision problems.
I'd been having regular eye tests, no issues raised, changed optician when I moved for a job and the new one pointed out that I was squinting to read the eyechart and needed glasses! It had obviously become a habit for me and I didn't realise.

For me it was very strange. I don't remember having a good vision at night as a child. Sometimes I was afraid of the dark, sometimes I liked not being able to see. I mean my parents and grandma and brother could see in dim light, I had struggle with it. It really became noticeable at the age of around 10 when I understood something is wrong, I was the only one who couldn't see at night of the friends group, yet no one paid attention to it because my eyesight was still good at school and for TV. Only at 12 I noticed I can't see from the back of the class and have to move closer to see. I had similar prescription to yours and it made some difference I didn't want to take my glasses off for the first few days (until I got bullied and never wanted to wear them).
Bad habits and genetics can make an impact to eyesight worsening. Still I would check the blood for sugar and insufficiencies that can also cause bad eyesight. Also I would recommend breaks from near work 20/20/20 rule (google it) and see if it improve your vision after a while, -0.50 can be a just a ciliary spasm (unless the optician/optometrist ruled this out). Don't wear your glasses full time (unless you really feel you need them full-time), wear them for distance only.
I wouldn't recommend glasses at such a low prescription unless really necessary, usually I would go on working on habits first and trying to avoid glasses if possible. Sudden change may be a sign of a ciliary spasm that causes pseudo-myopia that should not be treated with glasses. Also it could be a sign of deficiencies in vitamins and minerals (zink/iron, b12 etc...). This are the things to check. Although, I am pretty sure it just a late teenage myopia caused by screens and intensive close work (mostly phone) and bad habits (sleep pattern, stress ect...), usually people notice problems at around -1~-1.5. Even I when I noticed I had problems I was around your prescription but could manage very well without glasses until I was around -2 or something, like most people see worse and still function well without knowing they have a problem seeing.
PS
I'm an optometrist.

I'm not criticizing any of your opticians, both are sort of right.
If your vision acuity is good enough to function and even drive without glasses and you don't notice any issue, most likely you don't need glasses. 6/9 vision is a good vision, it is not always needed to push you to a 6/6 vision (or even better). It is important to meet your needs and wants. If you really want a better vision glasses are good for you, if you only squint to see the bottom row and never squint when you are outside or at school, you don't need the glasses and they are just going to make your eyes more and more dependent on them.
My approach is more "not broken - don't fix it". If a patient doesn't complain and the issue is really minor, no need to fix it. Patients like this are always hard for me. I don't like to prescribe glasses for minor errors unless really necessary.

I get this, I don’t really wear my glasses simply because I find it uncomfortable. However I do struggle to see quite badly which is odd on such a low prescription- not even squinting helps, it’s just as blurry when I try it. I often feel very overwhelmed outside because I simply can barely see long distance when this was never the case before for me and it makes me feel very disorientated.