American Board of Ophthalmology (ABO) Practice Exam

What is the minimum center thickness for a minus lens in a pair of industrial safety glasses?

1. 2.0 mm

2. 3.0 mm

3. 4.0 mm

4. 5.0 mm

The correct answer is: 3.0 mm

The minimum center thickness for a minus lens in industrial safety glasses is often specified to ensure adequate strength and safety in potentially hazardous environments. A thickness of 3.0 mm is commonly accepted as a baseline for minus lenses, as it provides a balance between safety, durability, and optical clarity. Thicker lenses may be required for higher prescriptions or specific industrial applications to prevent breakage and maintain integrity under impact. The choice of 3.0 mm stems from standards set by organizations governing industrial safety glasses, which dictate minimum requirements to protect workers effectively. This choice also considers factors like lens material, which can influence overall durability and impact resistance, with some materials being able to provide sufficient protection at a lower thickness. In contrast, thinner lenses might compromise safety by being more susceptible to breakage during an impact. Therefore, the 3.0 mm thickness is strategically chosen to meet safety criteria while considering practical aspects of comfort and wearability in protective eyewear.