How to buy the right sunglasses for your eyes: Doctor explains

While stepping out in the blazing sun makes sunglasses a must-have accessory for style and comfort, choosing the wrong pair can have devastating consequences for your vision. Ideally, a high-quality pair of sunglasses must perform three key functions: reduce excess glare, block harmful ultraviolet (UV) radiation, and filter out harsh reflections from flat surfaces like water, sand, or roads. Sunglasses that successfully tick all three boxes are the only ones you should be putting on your face. 

Unfortunately, most cheap, fashionable sunglasses sold on the roadside or at beaches are abysmally poor quality. Many people wear them solely as a budget-friendly style statement, completely unaware that they are slowly but surely destroying their eyesight. Let's look closely at how these sub-standard lenses affect your eyes, and why opting for polarised protection is crucial for your long-term ocular health. Dr Thomas Kuriakose, Senior Consultant at Giridhar Institute in Kochi, explains what you need to be careful about. 

Why low-quality sunglasses do more harm than good
Our eyes possess a brilliant natural mechanism to regulate light. In bright conditions, the pupil constricts to limit light entry, while in dim environments, it dilates to let more light in. When you wear dark, cheap sunglasses that lack proper UV filters, the lenses create a dark environment for your eyes. This tricks the eye, causing the pupil to dilate to its maximum size in an attempt to let in more light.

The danger of invisible UV rays
While these cheap lenses succeed in dimming the bright sunlight, they do absolutely nothing to filter out invisible ultraviolet radiation. With your pupils now fully dilated, a significantly greater amount of harmful UV light can penetrate deep into your eyes, directly striking the lens and retina. This makes wearing cheap, dark sunglasses far more dangerous than wearing no sunglasses at all, as it completely bypasses your eyes' natural defensive mechanism of pupil constriction.

The long-term health risks
Regular exposure to UV rays in this manner can lead to severe eye fatigue, premature cataracts, and permanent damage to the retina, including macular degeneration. In short, using sub-standard eyewear is a direct threat to your eyesight.

What are polarised sunglasses?
Polarised lenses are engineered with a special filter that blocks glare—the intense, blinding light that reflects off flat surfaces like roads and wet surfaces, or off water. By filtering out these horizontal reflections, polarised lenses allow you to see with immense clarity without straining your eyes. They are highly recommended for long-distance driving, outdoor sports, and anyone working near bodies of water.

Because they use specialised tints, you might notice a very slight alteration in how colours appear through polarised lenses. However, their superior eye protection far outweighs this minor detail.

What about high-quality non-polarised sunglasses?
A premium pair of non-polarised sunglasses from a reputable brand will still offer 100% UV protection (often labelled as UV 400). While these will fully protect your eyes from radiation, they lack the polarising filter needed to eliminate horizontal glare from roads or water. They are, however, perfectly safe and adequate for regular daily wear.

Important tips to keep in mind when buying sunglasses
1. Always check for labels that guarantee 'UV 400' or '100% UV Protection' before buying any pair of sunglasses.
2. Always purchase your eyewear from a certified optical shop. Avoid buying cheap, unbranded sunglasses from roadside stalls or at the beach, even if it is just for a quick holiday photoshoot.
3. When visiting an optician, ask to check the polarisation. Reputable shops always have specific testing cards that visually demonstrate whether a lens is truly polarised.