Do Regular Prescription Glasses Block Blue Light? How to Test If Your Lenses Have Blue Cut

The baseline lens material used in standard eyewear is CR-39 monomer (index 1.50). In its untreated state, CR-39 only blocks UV radiation up to $355\ \text{nm}$, transmitting almost $100\%$ of high-energy visible light from $400\text{ to } 455\ \text{nm}$ directly into your eye:

$$\begin{cases} \mathbf{\text{Standard 1.50 CR-39:}} & \text{Blocks UV to } 355\ \text{nm} \implies \mathbf{\text{Transmits 95\% of HEV Blue Light (Zero Protection)}} \\ \mathbf{\text{High Index 1.60/1.67 Resin:}} & \text{Blocks UV to } 400\ \text{nm} \implies \text{Natural UV shield, but transmits 420-450 nm blue} \\ \mathbf{\text{ELLASUV BluePro:}} & \mathbf{\text{Blocks UV to 400 nm AND filters 415-455 nm blue by 30-40\%}} \end{cases}$$

Unless your optician specifically dispensed a blue-cut product, your standard glasses do not provide HEV screen defense.

1. The White Screen Reflection Test: Open a full white screen on your laptop or phone. Hold your glasses at arm's length against the white screen and tilt them. If the lenses cast a subtle, very soft warm/champagne tint on the white surface behind them while reflecting a soft blue/green glint off the front surface, they have blue-filtering technology.
2. The Blue Laser Pen Test: Many online kits come with a $405\ \text{nm}$ blue-violet laser pointer and a photosensitive test strip. Shine the laser through your lens onto the strip. If the strip remains pure white underneath the lens while turning deep purple outside it, your lens completely stops $405\ \text{nm}$ radiation.
3. Check Your Lab Authenticity Card: Reputable lens manufacturers provide a warranty card (such as the ELLASUV Certificate of Authenticity) specifying the exact coating batch (e.g., 'BluePro Green HMC' or 'BluePro mGold').

YES! Photochromic lenses (like ELLASUV Photogrey HMC) are exceptional blue light blockers. Indoors in their clear state, the photochromic naphthopyran dye molecules naturally absorb approximately $20\%$ of high-energy blue light. When you step outdoors and they darken into sunglasses, their blue light blockage jumps to over $85\%$, providing unmatched dual indoor/outdoor protection.