An apprentice at my dispensary brought in a practice exam from another optician at another store. Copies were eagerly made and handed out to the other trainees. Soon I was being asked questions:

  • How come so many of these questions are about glass?
  • What’s a kryptok?
  • Why do we have to know about mirrors?
  • Do they really drop steel balls on lenses?

I looked at the question list and couldn’t help comparing it to the questions I studied from back in 1986. Glass lenses, archaic rimless frames, fused bifocals, and LOTS of geometric optics. Most of the questions could probably be skipped, and I told them so. Although it couldn’t hurt to learn about angles of incidence and refraction and how they relate to the “normal,” any questions concerning mirrors, telescopes and candlepower can probably be ignored.

But not ANSI.

The problem is, however, that ANSI standards, as well as OSHA requirements (and the Z87 standards that have been incorporated into them,) HAVE changed with time.

If you are studying from old sources, you may be learning the WRONG THINGS.

ANSI standards have changed over time.

If you are studying from old notes or old test questions, you should disregard anything that has to do with ANSI unless you verify the date of the material!

When I started in optical, ANSI standards were tighter. A -0.25 cylinder axis to be within 7° for it to pass inspection. Now it is 14°. A -0.50 cyl had to be within 5°. Now it is 7°.

Chances are, though, that if you are doing final inspection on a routine basis, there is most likely a modern chart hanging on the wall near the lensometer that you can refer to in cases where you are not sure of the tolerances. You probably don’t know that those standards date from 2007, much less that before that the standards were stricter.

If you see questions on some old practice test that don’t make sense according to that chart, chances are whatever material you are working with is obsolete, at least in regard to ANSI.

This is particularly important to remember when dealing with safety eye wear questions.

The most recent Z87 safety standards date from 2003.

Most of the Z87 questions I have seen on old practice tests should be disregarded. So much has changed!

It used to be that there was ONE drop ball test and two standards of lens thickness: one for safely and one for dress. Now, it is quite different, and it is truly in your best interest to study from material that reflects this.

Where once there was one set of standards for safety eyewear, there are now TWO levels of safety standards: Basic Impact, and High Impact.

Basic Impact safety lenses are glass. They are for patients who don’t actually NEED a high impact lens, and who work in conditions which would cause plastic and poly lenses to scratch. Oily, dusty work environments, or those containing mist or chemicals might make it best for a patient to purchase a pair of Basic Impact safety glasses.

High Impact safety lenses are composed of any lens material which would pass the High Impact testing requirements. We usually see these as polycarbonate or Trivex®.

High Impact safety lenses must only be inserted into frames that are designated for High Impact use. If the frame only has Z87 printed on it (on the front as well as the temples) it cannot have High Impact safety lenses inserted into it. A frame must have the Z87-2 marking in order to be sold with High Impact safety lenses.

High Impact safety lenses are also marked differently. Not only do they have to have the manufacturer’s monogram, but they also have to have a + next to that monogram. If that plus sign is not there, it is a Basic Impact safety lens. Period.

Lens thickness requirements for Z87 lenses

Disregard any practice question you find on old, or possibly old, ABO prep tests if the question involves safety lens thickness! It’s changed.

Basic Impact safety lenses must have a minimum thickness of 3.0mm unless the lens power is +3.00D or higher. In the higher plus powers, the minimum thickness can be 2.5mm.

High Impact safety lenses have a minimum thickness requirement of 2.0mm with NO EXCEPTIONS.

Testing requirements for safety lenses and frames

Lots of those old practice tests have questions on the drop ball test that are outdated. There are now several levels of drop-ball tests. Here they are:

  1. Drop ball test for dress eyewear: a 0.56 oz 5/8 inch steel ball dropped from a height of 50 inches.
  2. Drop ball test for Basic Impact safety lenses: a ONE inch steel ball dropped from a height of 50 inches.
  3. High Velocity Impact test for High Impact lenses: a 1/4 inch steel ball hitting the lens at 150 feet/sec.

The High velocity Impact test is also performed on safety frames. If the frame is to be designated High Impact Z87-2, it must be able to withstand a series of 1/4 inch steel balls travelling at 150 ft/sec and hitting the frame (with lenses in it!) in 20 different places. The frame and the lenses can’t break and the lens can’t come out.

There is also a High Mass Impact test performed on High Impact safety glasses. A large, slow moving, pointed projectile one inch in diameter and weighing 17.6 oz is dropped through a tube onto the glasses from a height of 51.2 inches. The lens has to stay in the frame and not break.

On your ABO you MAY have to know all these particulars: the weight of the steel balls, how large they are, and how far they must be dropped. You may have to know the particulars of the frame tests as well. Or.. you might luck out and just have to know that there are two levels of safety eyewear.

It would be to your advantage to learn these and all other particulars of safety eyewear and the regulations concerning them.

Sources for Z87 safety eyewear study

So where can you find all these updated regulations? Why, a textbook, of course! The book I know for sure has all the updated information is the third edition of System For Ophthalmic Dispensing, by Brooks and Borish. You can also go to the website of ANSI… but if you buy the book it generally is less expensive than downloading ANSI and you get everything ELSE optical related as well!

I also recommend you take practice tests that contain all the latest information. Go to to get the best exam prep material available!