History of Bifocals: Franklin's Invention to Modern Progressives

Benjamin Franklin invented bifocals circa 1784 (age 78) to avoid switching between distance and reading glasses.

Original Design

• Two half-lenses (distance upper, reading lower) cut and mounted in single frame.
• Sharp dividing line (segment line).
• Franklin called them "double spectacles."

Evolution

• 19th century: Fused bifocals (cemented), then one-piece casting (John Isaac Hawkins, 1827).
• Segment shapes: D-seg (flat-top, 1920s), round, executive (full-width), curved-top.
• Materials: Crown glass → CR-39 plastic (1940s) → polycarbonate, high-index, Trivex.
• Coatings: Anti-reflective, scratch-resistant, photochromic, blue-light filter.

Modern Alternatives

• Progressive addition lenses (PALs): Gradient power (distance → intermediate → near); no visible line; natural vision zones. First commercial: Varilux (1959).
• Multifocal contact lenses: Simultaneous vision (concentric rings) or translating (rigid gas permeable).
• Monovision: One eye distance, one near (contacts or refractive surgery).
• Accommodating IOLs / EDOF IOLs: Cataract surgery options.

Clinical Selection

• Bifocals: simple, cheap, distinct zones; image jump at segment.
• Progressives: cosmetic, continuous vision; adaptation required; peripheral distortion.
• Occupational/progressive: computer + near (office lenses).