I am planning to start going to the gym in a few days. I am an 18 year old boy. I wear spectacles with power of -4 in both eyes. I have a somewhat skinny physique, but I really want to improve it. My fear is that I have heard that people who wear spectacles should not go to gym, as it may lead to eye problems. Is it actually an issue?
People with spectacles are built the same way as everyone else, and will benefit equally from going to the gym and working out.
Whoever told you that bespectacled people should not go to the gym is wrong. Next time, ask them why they think that. You'll find that they have no real scientific knowledge.
Should I start gyming or not
Yes. You should start gyming.
I believe you're talking about retinal detachment and the possible link to high exertion. Yes, it is possible. Lifting heavy weights, particularly if using the Valsalva maneuver, holding your breath to increase your lift. Basically, it increases overall blood pressure, which includes ocular pressure. High pressure in the eyes is linked to retinal detachment, glaucoma, and "floaters" in your vision. This is supported by "Occupational Lifting Tasks and Retinal Detachment in Non-Myopics and Myopics: Extended Analysis of a Case-Control Study", which concluded that there does seem to be a link.
For all indexes, the most exposed subjects showed an increased risk of retinal detachment compared with the unexposed (index 1: OR 3.57, 95% confidence interval [CI] 1.21-10.48; index 2: OR 3.24, 95% CI 1.32-7.97; index 3: OR 2.23, 95% CI 1.27-8.74) and dose-response relationships were apparent.
That said, unless you have other markers such as high intraocular pressure, your eyesight does not make you more disposed to this than other people in the gym. High degree myopia (-6 and higher) is associated with increased risks of glaucoma and retinal detachment. But you don't have it that bad yet, and if you lift more modestly, and avoid holding your breath, your risk is minimal.
I personally advise getting a strap for the glasses that goes around the back of your head, because having your glasses fall off of your face mid-lift while bending forward can throw you off. Don't tighten it all of the way because it will increase fogging, just enough that your glasses, if they slide forward, stay on your face.
I wear spectacles with half of the power that you have and have been gymming for a long time. I have not faced any problems till date and know of people having power comparable or more than what you have been regular to workout.
Retinal detachment is the term I read for the first time and looked up briefly. It does not include working out as one of the risk factors though extreme high speed sports like bungee jumping, skydiving etc are included.
You should start slow and perform progressive overload both for strength and cardiovascular conditioning to let your body adapt. This advise is same for all beginners irrespective of them being spectacled or not.