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Would Your Sunglass Lenses Survive a Run-In with a Tree Branch?

By Kirsti Smouse

October 7, 2015

Would Your Sunglass Lenses Survive a Run-In with a Tree Branch?

By Kirsti Smouse

October 7, 2015

Impact Resistance Explained

Eyes are a very precious commodity, and something you probably take for granted. But lest you end up like Colonel Tigh, One-Eyed Willy, or Nick Fury, it might be time to pay them a little more attention.

Sure, those guys all rock the one-eyed look like nobody’s business, but they’d probably have preferred to keep both eyes intact.

Luckily, you’re not without options when it comes to protection in your eyewear.

While the size of a lens plays a part in how much coverage you’ve got, the most important factor is the ability of the lens to absorb a blow, otherwise known as its impact resistance.

In the US, there are two levels of impact resistance for sunglass lenses for commercial use — basic impact resistance and high-impact resistance.

This article will go over the tests needed to comply with these certifications and their real-world implications.

Basic Impact Resistance: Z80.3

The ANSI Z80.3 seal of approval encompasses more than impact resistance, testing things such as UV protection and clarity. But for the purpose of this post, we’ll focus on the impact resistant portion of the American National Standards Institute (ANSI) rating.

The requirement for lens strength or safety was actually set by the Federal Drug Administration (FDA) and is the most severe impact requirement of any nation. The test, commonly known as the “drop-ball” test consists of a 5/8 inch steel ball weighing .56 ounces (15.87 g) being dropped on the lens from a height of 50 inches (127 cm).

The ball is usually guided by a tube that must end at least four inches (10 cm) above the lens and cannot impede the progress of the ball in any way.

To pass the test, the lens must not fracture, chip, or crack.

A real-world scenario of this situation would be equivalent to your 4-foot tall nephew standing over your prone body and dropping a marble onto your face. A more likely scenario is falling rock while you're belaying or debris thrown up in a strong wind.

High Impact: Z87.1

Often associated with safety glasses, sunglasses that meet the ANSI Z87.1 standards are relevant to far more than OSHA (Occupational Safety and Health Administration) regulated work environments. In order to receive this certification, lenses must be tested in the frames and must pass two different levels of testing for impact resistance — high mass and high velocity.

High Mass:

In this test, a steel spike one-inch in diameter and weighing 17.6 ounces (498 grams) is dropped through a tube from a height of 50 inches (127 cm) onto a lens mounted in a frame. The frame is "worn" by an artificial head form.

To pass, the lens cannot crack, chip, or break and it must stay within the frame. Also, the lens must not make any contact with the head form.

This would be equivalent to crashing your bike and falling headfirst into your handlebars or colliding with a low-hanging tree branch.

High Velocity:

This test involves shooting a quarter-inch steel ball at the lens and frame at a velocity of 150 feet per second (roughly 102 miles per hour or 164 kilometers per hour) from a distance of just under 10 inches (25 cm).

The test is repeated multiple times (each time with a new frame and lens) at different angles and positions of impact. To pass, the lens must not crack, chip or break, and it must not become dislodged from the frame.

Outside the lab, this is equivalent to a tipped foul ball, a tricky grounder that gets away from you and pops up into your face, or catching some frags on the shooting range.

Also, it should be noted that in order to be Z87.1 certified both the frame AND the lenses must pass the test. You can install Z87.1 lenses into frames without this safety rating, but this does not make them compliant with ANSI and OSHA requirements for safety eyewear.

Fingers crossed, you'll never have to find out if your sunglasses could take a punch. But if you're going to be wearing your sunglasses for any high-impact activities, it would be best to stick with the Z87.1 rating. Just in case.

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