2. Heat can distort them, so don't leave them lying around in strong sunlight, or on hot surfaces such as car dashboards.

3. Don't carry them in your pocket or loose in bags as they could get crushed of scratched easily.

4. Sorry - but wearing your glasses pushed back into your hair distorts their shape.

5. Wash them occasionally in warm soapy water, and rinse your shades well if they've been in salt water.