In the late 1930s, polymethyl methacrylate (PMMA) plastic began replacing glass as the material of choice for scleral contact lenses. However, for many patients, wearing time continued to be limited to two to four hours due to the onset of corneal edema.

This changed in 1948 with the advent of Tuohy Corneal Contact Lenses (Fassenden, 2015). The original Tuohy lens was 11mm to 12mm in diameter and was fit 0.30mm flatter than flat K. Clinicians quickly recognized the physiologic benefits of this new corneal design, as well as its limitations secondary to the large posterior optical zone that necessitated the flatter than flat K fitting philosophy.

The first modern corneal contact lens became available in the early 1950s with the introduction of the Butterfield Design, incorporating a smaller posterior optical zone and multiple spherical peripheral radii to facilitate tear flow and better align the flatter periphery of the cornea.

With this discovery, eyecare practitioners were able to move into the “on-K” era of corneal contact lens fitting. Yet, despite this innovation, limited wearing time secondary to corneal edema continued to be a problem for many patients. Beginning in the mid-1950s, lens manufacturers turned to innovative new designs to address several of the shortcomings related to the early PMMA corneal lenses.

The Stimson Keraform Lens Design

The Keraform was introduced in 1953 by Dr. Neil Stimson (Stimson, 1953). The contact lens had four equally spaced projections on the posterior periphery resting on the corneal surface (Figure 1A). The posterior contact lens projections were designed to prevent or minimize lens rotation, allowing stabilization when correcting residual astigmatism.

The Vent Air Design

The Vent Air contact lens design was released in the U.S. in the early 1950s (Bowden, 2009). The design incorporated four large “vents” in the posterior periphery to facilitate tear and oxygen exchange (Figure 1B). Manufacturing of the design was limited by a franchising agreement with Vent Air Corp. The contact lens was accompanied by an aggressive consumer advertising campaign that made the lens design well known to the public.

The Spiro Vent Lens Design

In 1959, Dr. Stanley Gordon filed a patent for his Spiro Vent design, which incorporated five “jet-propulsion” depressions on the posterior lens surface to promote lens rotation and tear exchange beneath the lens (Stanley, 1961) (Figure 1C).

The Astrocon Lens Design

In 1965, a third “vented” contact lens design called Astrocon was introduced by Dr. Irving Adler (Adler, 1965) (Figure 1D). It incorporated a series of grooves and channels in the posterior surface with a “scalloped” edge profile that matched the number of groves desired, from one to four grooves.

Today, we can only admire the creative contact lens designs our forefathers created in their quest to conquer lens orientation and PMMA’s greatest nemesis, corneal edema. CLS

References

1. Fassenden M. How Contact Lenses Were Made in 1948. Smithsonian Magazine. 2015 Oct 23.
2. Stimson NO. Corneal contact lens. US Patent #US2653515A. 1953 Sep 29. Available at patents.google.com/patent/US2653515 . Accessed Nov. 1, 2022.
3. Bowden TJ. Contact Lenses the Story: A Historical Development of Contact Lenses. Bower House Publications. 2009: 615.
4. Standley G. Corneal contact lens with spiral vent ducts. US Patent #US2989894A. 1961 Jun 27. Available at patents.google.com/patent/US2989894 . Accessed Nov. 1, 2022.
5. Adler I. Optical contact lens. US Patent #USD203357S. 1965 Dec 28. Available at patents.google.com/patent/USD203357S . Accessed Nov. 1, 2022.