When buying sunglasses, it is essential to prioritize UV protection to safeguard your eyes from long-term damage. Look for lenses that block 100% of UVA and UVB rays, and check for the UV40 or UV400 rating. Additionally, consider factors such as frame quality, lens material, anti-reflective coating, polarization, and construction. It is also important to try on sunglasses in person to ensure a comfortable fit and proper alignment. Finally, consider shopping from reputable brands and retailers to ensure the quality of your sunglasses.