Powell Johnson of Barton, Ala., knew that exposure to intense glare and heat was harmful to the eyes and vision, and wanted to do something about it. On Nov. 2, 1880, he received a patent for an Eye-Protector. Johnson designed his Eye-Protectors “for use of furnace-men, puddlers (iron manufacturing workers who used a furnace to convert pig iron into wrought iron), firemen, and others exposed to glare of strong light, as well as persons of weak sight,” according to the patent. The protector had two sets of circular wire frames, separated by “a short distance,” with hinged temples on the inner frame only and semi-opaque cloth disks inserted in both frames to protect the eyes from bright light. They were the first of their kind.
Although they did not provide impact protection, the eyewear offered some protection from heat as well as glare. Another piece of the same cloth covered the bridge of the frame closest to the face, presumably to prevent injury from the metal frame if it became hot. The cloth could vary in thickness and color, depending on its use, and the cloths on the inner frames had small slits in the center for better visibility. To add versatility to the protector’s use, the eyewires of the front frame were hinged with a clasp in the center. This allowed the front filters to either remain fixed or swing to the sides like side shields, providing additional protection or to allow more light in if needed.
For “persons of weak sight,” the same eyewear was used, but the inner cloths had pinholes in the center instead of slits, “enabling them to see through the said hole and still have the eye shaded from the light.” One wonders if Johnson knew about the pinhole effect. The pinhole effect is an optical concept suggesting that the smaller the pupil size, the less defocus from spherical aberrations is present. When light passes through a small pinhole or pupil, all unfocused rays are blocked, leaving only focused light to land on the retina to form a clear image. Pinhole occluders are used today and work along the same basis as pupil constriction in bright light, causing an improvement in visual acuity. Through a smaller pupil, the effects of minor ocular irregularities, such as refractive error or paracentral cornea or lens opacities, are diminished for better vision.
Unfortunately, not a lot is known about Johnson’s personal life or his road to inventing the Eye-Protector, but he is credited as having developed the first known functional safety eyewear.
• Linda Conlin
Pro to Pro Managing Editor
[email protected]
