Quick answer: Aspheric lenses have a front surface whose curve changes gradually from the centre to the edge, rather than following one constant curve like a standard spherical lens. This makes them flatter, slimmer and lighter, and they may reduce the way strong lenses make your eyes look bigger or smaller. They make the most difference for stronger prescriptions, especially long-sighted (plus) ones. With a mild prescription, the difference is smaller and you may not need them.
If you’ve been comparing lenses, you may have come across the term “aspheric” and wondered whether it’s worth paying for. This guide explains what aspheric lenses are, how they differ from standard lenses, who benefits most, and what to consider before choosing them.
What Is an Aspheric Lens?
The word “aspheric” simply means “not spherical”. It describes the shape of the lens surface, not the material it’s made from.
Spherical Lenses
Most conventional glasses lenses have a spherical front surface. That means the curve is the same across the whole lens, like a section cut from the surface of a ball.
Aspheric Lenses
An aspheric lens has a more complex front surface, where the curve changes gradually from the centre of the lens towards the edge. This allows the lens to be made flatter than a spherical lens with the same prescription.
Aspheric Design vs Lens Index
Aspheric design and lens index are two different things. The lens index describes the material, and how efficiently it bends light. The aspheric design describes the shape of the surface. They’re often combined: an aspheric design in a high-index material gives a noticeably slimmer, lighter lens than a conventional lens.
What Are the Benefits of Aspheric Lenses?
Flatter, Slimmer and Lighter
Because the surface is flatter, an aspheric lens can be slimmer and lighter than a spherical lens with the same prescription. Aspheric designs are slimmer for virtually all prescriptions, but the difference is most noticeable on stronger ones.
A More Natural Look
Strong long-sighted (plus) lenses can make your eyes look larger to other people, and strong short-sighted (minus) lenses can make them look smaller. Aspheric designs may reduce this effect, so your eyes look more natural through your glasses.
Clearer Vision Away From the Centre
Aspheric designs can reduce the distortion that occurs when you look through the lens away from its centre, which may improve the clarity of your peripheral vision.
Who Benefits Most From Aspheric Lenses?
Stronger Prescriptions
Aspheric lenses are most likely to benefit people with a stronger prescription, typically ±4.00 or more. The higher your prescription, the more difference the flatter design makes to the thickness, weight and look of your lenses.
Long-Sighted (Plus) Prescriptions
The slimming effect is especially noticeable on strong plus lenses, which are thickest in the centre. Aspheric designs can make these lenses much less bulky.
Short-Sighted (Minus) Prescriptions
For minus lenses, which are thickest at the edges, the difference is smaller but can still be noticeable in edge thickness.
Mild Prescriptions
If your prescription is mild, a standard lens is likely to be thin and light already, so the benefit of an aspheric design is smaller. Many people with low prescriptions may not need them.
Things to Consider Before Choosing Aspheric Lenses
They Usually Cost More
The more complex curves make aspheric lenses more expensive to produce, so they usually cost more than conventional lenses.
An Anti-Reflective Coating Is Recommended
Because aspheric lenses are flatter and sit closer to the face, an anti-reflective coating is typically recommended to reduce reflections. At Glasses Store, our MAR anti-reflective coating comes as standard on 1.60, 1.67 and 1.74 index lenses and is available as an upgrade on 1.50.
Accurate Measurements Matter
Fitting aspheric lenses calls for more careful measurements than standard lenses. If you’re ordering online, double-check your pupillary distance (PD). Our guides on what PD is and why it matters and how to measure your PD at home explain how.
Frame Choice Matters
Frame choice is more important with aspheric lenses, and many wearers prefer frames that aren’t too large. A well-fitting frame in the right size helps keep the lenses correctly positioned. Our guide on finding your glasses size from your current frames can help.
Are Aspheric Lenses Available for All Lens Types?
Aspheric designs are available for single vision, varifocal and bifocal lenses. Most are made in high-index materials, though standard plastic versions also exist.
So, Do You Need Aspheric Lenses?
A simple way to decide:
- Mild prescription (around ±2.00 or less): a standard lens is usually fine, and the benefit of aspheric is usually smaller.
- Moderate to strong prescription (±4.00 or more): aspheric lenses are more likely to make a worthwhile difference to thickness, weight and appearance.
- Strong long-sighted prescription: this is where aspheric lenses tend to make the biggest difference.
Choosing the right lens index also makes a big difference for stronger prescriptions. Our guide to high prescription glasses explains how index and frame choice work together.
Ask Before You Order
If you’d like to know whether an aspheric lens design is available for your prescription, or whether it would make a difference for you, contact our team before you order.
Frequently Asked Questions
What is the difference between aspheric and spherical lenses?
A spherical lens has the same curve across its whole front surface. An aspheric lens has a curve that changes gradually from the centre to the edge, which lets it be flatter, slimmer and lighter.
Are aspheric lenses worth it?
They’re most worthwhile for stronger prescriptions, typically ±4.00 or more, and especially for long-sighted prescriptions. For mild prescriptions the difference is smaller.
Are aspheric lenses the same as high-index lenses?
No. High-index describes the lens material; aspheric describes the shape of the surface. They’re often combined to make slimmer, lighter lenses.
Do aspheric lenses make your eyes look smaller or bigger?
Aspheric designs may reduce the effect strong lenses have on how your eyes look, so they appear more natural than through conventional lenses.
Do aspheric lenses cost more?
Yes, they usually cost more than conventional lenses because their more complex curves are harder to produce.
Do aspheric lenses need an anti-reflective coating?
An anti-reflective coating is typically recommended, because the flatter lens sits closer to the face and can show more reflections.
Can I get aspheric varifocals?
Aspheric designs are available for single vision, varifocal and bifocal lenses. To check what’s available for your prescription, contact our team before you order.
Do I need aspheric lenses for a mild prescription?
Usually not. With a mild prescription, standard lenses are already fairly thin and light, so the benefit is usually smaller.
Thinner Lenses, Clearer View
Aspheric lenses use a flatter, gradually changing curve to make lenses slimmer and lighter and to give a more natural look. They make the biggest difference for stronger prescriptions, particularly long-sighted ones. Whatever your prescription, the right combination of lens index, coating and frame matters most. Explore our lenses hub or browse our full range of glasses.
