High Index Lenses

How Thick are 1.74 High Index Lenses

With such a “focus” – pardon the pun – on 1.74 high index lenses and the reduction in thickness that they provide, you may wonder: just how thick are 1.74 high index lenses? The answer depends upon your exact prescription.

How Thick are 1.74 High Index Lenses

The benefits of high index lenses in general – and 1.74 high index lenses specifically – really come into play when your prescription is in a higher range. Strong prescriptions demand that larger, deeper curves are cut into the lens material. Think of it as carving a bowl from stone – you’d need more stone to carve out a larger soup bowl than you’d need to carve a more shallow soup bowl. Stronger prescriptions are like that deeper bowl…thicker plastic or glass is necessary to create them.

High index lens material is designed to be thinner than conventional plastic or glass. How much thinner? Lenses that feature a refraction index of 1.70 or higher – and that, of course, includes 1.74s – are, at a minimum, half as thin as standard plastic lenses. That means considerably less overall lens material is required to produce your prescription…and less material means lighter weight as well as thinner lenses.

If you’re curious about where 1.74 high index lenses place on the thinness scale, see the chart below. Remember that the higher the index number, the thinner the lens.

• Conventional Plastic             Index Rating 1.50
• Conventional Glass               Index Rating 1.52
• Trivex                                    Index Rating 1.53
• Mid-Index                             Index Rating 1.56
• Polycarbonate                       Index Rating 1.59
• High Index Plastic 1.6          Index Rating 1.60
• High Index Plastic 1.67        Index Rating 1.67
• High Index Plastic 1.7          Index Rating 1.70
• High Index Plastic 1.74        Index Rating 1.74
• High Index Glass 1.8            Index Rating 1.80
• High Index Glass 1.9            Index Rating 1.90

As you can see, 1.74 high index lenses score very high on the thinness scale, and are the thinnest plastic lenses available. If your prescription demands thick, heavy lenses and you’d like to find out more about reducing them with high index material, have a look around our website and explore your options. You’re likely to find that high index lenses will not only reduce weight and thickness, they’ll also open up to you a world of frame styles that conventional plastic or glass lenses could not allow.