Firefly - Cat Eye Sunglasses

Lens Index measures how efficiently light bends through the prescription lens. The higher a lens' index is, the thinner it becomes.

• Same lens index, higher SPH = thicker lens.
• Same SPH, higher lens index = thinner lens.

Quick Reference Chart

1.56 Index (Standard)

• Best for: Low prescriptions | SPH Range: 0 to ±2.00.
• Pros: Affordable.
• Cons: Thicker edges for stronger prescriptions.

1.61 Index (Mid-Range)

• Best for: Mild to moderate prescriptions | SPH Range: 0 to ±4.00.
• Pros: Around 20-30% thinner than 1.56, good clarity, widely available.
• Cons: Slightly more expensive.

1.67 Index (Thin & Light)

• Best for: Moderate to high prescriptions | SPH Range: ±2.00 to ±6.00.
• Pros: Around 40% thinner than 1.56, lightweight.
• Cons: Higher cost.

1.74 Index (Thinner)

• Best for: High prescriptions | SPH Range: ±4.00 and above.
• Pros: Thinnest option (around 50% thinner than 1.56), lightweight.
• Cons: Most expensive.

Additional Tips

• SPH+CYL: If both SPH and CYL are positive and SPH plus CYL has been over +4.00 (such as SPH +3.00, CYL +1.25), opt for higher index(1.67/1.74) for thinner lenses and comfortable wear.
• Frame Size Matters: Larger frames make lenses appear thicker - opt for higher index(1.67/1.74) if needed.
• Ask Your Optician: For astigmatism(CYL) or bifocals, they may recommend adjustments.

Note:

• For some high prescriptions, an additional charge may apply as it requires higher customizations. If necessary, we will email you for confirmation before processing your order.
• If there are ADD numbers in your prescription, progressive lenses or bifocal lenses are recommended.