There are several distinctions between dress eyewear (eyewear worn for everyday purposes) and safety glasses (eyeglasses worn specifically for eye protection).  No matter how sturdy a pair of eyeglasses appear, they don't qualify as safety glasses unless specific criteria are met.

OSHA Regulations for Safety Eyewear

In the United States, the federal government sets guidelines to help protect workers from on-the-job injuries.  The Occupational Safety and Health Administration (OSHA) is the agency charged with regulating safety practices in the workplace and in educational settings.

OSHA rulings have the same power as law.  To insure businesses are in compliance with OSHA safety regulations, the agency makes unannounced visits to workplaces.  If violations are found, the offending companies face substantial fines and other corrective actions.

For its regulatory purposes, OSHA has adopted safety eyewear standards that have been formulated by the American National Standards Institute (ANSI).  ANSI is a non-governmental body that creates safety standards for a wide variety of products and conditions.

The ANSI standard that relates to safety glasses is:

• ANSI Z87.1  Practice for Occupational/Educational Eye and Face Protection   

Other ANSI standards that pertain to eyewear include:

• ANSI Z80.1  Prescription Ophthalmic Lenses

• ANSI Z80.5  Dress Ophthalmic Frames

• ANSI Z80.2  Rigid Contact Lenses

• ANSI Z80.8  Soft Contact Lenses

• ANSI Z80.3  Nonprescription Sunglasses and Fashion Eyewear

• ANSI Z80.9  Low-Vision Aids 

The ANSI Z87.1 standard defines the specifications for acceptable safety glasses.  It also specifies the characteristics of acceptable nonprescription eye and facial protective devices.

Eyeglasses are not safety glasses unless both the lenses and the frame are in compliance with the following specifications for safety eyewear described in the ANSI Z87.1  standard.

Safety Lens Requirements

Lens Thickness

Prescription safety lenses must be thicker than prescription lenses for dress eyewear.  A prescription safety lens must have a minimum thickness of 3.0 millimeters (mm), regardless of the material from which it is made.  (Exception: Lenses for farsightedness that have a power of +3.00D or higher may have an edge thickness of 2.5 mm.)

Nonprescription safety lenses can be thinner than prescription safety lenses.  These lenses can be made as thin as 2.0 mm so long as they pass a more stringent impact-resistance test than that required for dress lenses.

Prescription dress lenses, on the other hand, have no minimum required thickness.  But they must pass a specific impact-resistance test mandated by the U.S. Food and Drug Administration (FDA).  This test (called the drop-ball test) requires dress lenses to be capable of withstanding the equivalent impact of a ?-inch steel ball dropped on the front surface of the lens from a height of 50 inches.  (By comparison, safety lenses must be able to withstand the impact of a 1-inch steel ball dropped from the same distance.)  Some dress lenses have a minimum thickness as low as 1.0 mm.

Lens Markings

All safety lenses must be etched with a marking that identifies the manufacturer.  This marking is applied after the lenses are cut (or edged) to fit into a safety frame.  This ID mark is usually placed in the upper, outer corner of the lens or at the 12 o'clock position of the lens near its upper edge.

A lens that is thick enough to be classified as a safety lens and strong enough to pass safety lens impact testing is not acceptable as a safety lens until it is marked with the required manufacturer identification.

Lens Materials

Safety lenses are usually made out of polycarbonate.  Polycarbonate is the lightest and most impact-resistant material available for eyeglass lenses. 

Though it's legal in the United States to make safety glasses out of glass or plastic materials, you should choose polycarbonate lenses whenever possible since safety eyewear with polycarbonate lenses will typically be safer and more comfortable.

Safety Frame Requirements

Frame Durability

Safety frames must pass of series of stress tests that are not required for dress eyewear.  Once a frame passes these tests, it can be marked as a safety frame.

Frame Markings

All safety frames have a "Z87" mark on the front of the frame and on the temples, indicating compliance with the ANSI Z87.1 safety eyewear standard.  If a frame doesn't have the "Z87" markings, it's not a safety frame.

Other Safety Eyewear Considerations

Side Shields

Side shields are not required on all safety glasses.  However, many people still sustain eye injuries when wearing safety glasses because objects hit their eyes from the side.  It's a good idea to add side shields to your safety glasses whenever practical to give your eyes added protection from flying debris.

More Style Choices

Safety glasses used to be easy to spot - they were big, thick, heavy and unattractive.  With the advent of new lightweight yet strong frame materials (i.e. titanium) and lightweight polycarbonate lenses, you now have a much wider variety of lighter and more attractive styles of safety eyewear to chose from.

The selection of safety eyewear can vary significantly in optical stores.  It pays to shop around to find comfortable and stylish safety glasses that fulfill your eye protection needs.