To adjust the size of a pair of eyeglass frames, it is important to be careful and make small adjustments at a time. If the frames are made of plastic, you should first warm them gently using warm water or a hairdryer so that the material becomes softer and easier to shape. Metal frames can usually be adjusted without heating, but you should still handle them with care.
If your glasses have adjustable hinges, such as spring hinges or small screws, you can fine-tune the fit in a more controlled way. Always start by checking if any screw has become loose, as this is a common reason why glasses feel loose or sit unevenly. If a screw is loose, you can gently tighten it using a small screwdriver (usually an eyeglass screwdriver). Tighten it until it feels secure, but not too tight, as the screw can be damaged.
If the glasses still feel too loose even after tightening the screws, you can adjust the temples by gently bending them, just like with regular frames. Spring hinges allow the temples to bend slightly outward, but they should not be forced beyond their intended range.
If the glasses feel too tight, you can carefully bend the temples outward a little. Be careful not to use the hinge as leverage—hold the temple arm itself when adjusting to avoid damaging the hinge.
If the glasses sit crooked, you can check that both hinges have equal tension. Sometimes one side may be looser than the other, which causes the glasses to tilt. Adjust or tighten the screws so that both sides feel even.