A case that fits the glasses inside it
Try the closed case with the glasses inside. The outer size does not tell you how much room the frame has.
Fit the folded frame
Fold the glasses in their normal way and place them in the case without forcing the arms or bridge. Close it gently. A case should not need pressure to shut over the frame, and the glasses should not rattle freely against hard surfaces inside.
Check deeper or strongly curved frames carefully. A slim case may be long enough but too shallow. If a cleaning cloth is kept inside, include it during the fit check; a bulky folded cloth can change the available space.
Keep the case's original lining intact. Do not add rough padding or leave grit inside to stop movement. If the lining is loose, damaged or dirty, follow the maker's care advice or replace the case with a suitable one.
Choose for the bag it goes into
A hard case can offer more physical protection than a soft sleeve when carried among other objects, but it still needs sensible placement. Do not put it beneath a heavy load or assume it can withstand any force because its shell feels rigid.
ZEISS advises storing glasses in a hard case and avoiding extreme heat. A case is not insulation against a hot vehicle dashboard. Keep both glasses and case out of unsuitable heat rather than relying on the cover to protect them.
Check the hinge or closure. It should stay closed during ordinary carrying but remain easy for the user to open. A snap that is difficult to operate may lead to the case being left open, which defeats part of its purpose.
Keep the inside clean
Empty dust and inspect the lining regularly using an appropriate method. Keep the cleaning cloth clean according to its instructions, and do not use an abrasive or dirty cloth on lenses. Follow the lens or optician's guidance for cleaning the glasses themselves.
If more than one pair is carried, use suitable separate compartments or cases rather than stacking frames together. Label similar cases discreetly so reading glasses and sunglasses can be found quickly. The useful case is one that fits the actual frame and is easy enough to use every time the glasses come off.
