Corneal contact lens

The corneal contact lens emerged because early contact lenses were too large and uncomfortable for daily wear—and the discovery that a lens covering only the cornea could correct vision transformed a medical device into a consumer product.

Contact lenses had existed since the late 19th century, but early designs were 'scleral' lenses—large shells covering the entire visible portion of the eye, resting on the white sclera rather than the cornea. Made from blown glass and later PMMA (polymethyl methacrylate, or acrylic glass), these lenses were effective but uncomfortable. They blocked oxygen from reaching the cornea, limited wearing time, and required careful fitting by specialists.

In 1948-1949, California optometrist Kevin Tuohy made a critical observation. While working with a plastic scleral lens that had broken, he noticed the remaining central portion—just the part covering the cornea—still corrected vision. He realized that lenses didn't need to cover the entire eye. A small lens floating on the tear film over the cornea alone could do the job.

Tuohy patented the corneal contact lens in 1950. These lenses were dramatically smaller—about 9-10mm in diameter compared to 20-25mm for scleral lenses. They were lighter, less intrusive, and could be worn longer because they allowed better tear exchange and some oxygen permeation around the edges.

The corneal lens transformed contact lens wear from a medical intervention for severe vision problems into a cosmetic alternative to glasses. Where scleral lenses required professional fitting and supervision, corneal lenses could be prescribed more broadly. The smaller size also made manufacturing easier and cheaper.

Subsequent innovations built on Tuohy's foundation. Soft hydrogel lenses (1971) improved comfort further. Gas-permeable materials allowed oxygen transmission through the lens itself. Extended-wear and disposable lenses followed. But the fundamental insight—that the cornea alone provided the optical surface needed for vision correction—came from observing a broken lens in 1948.