From their emergence in a rock crystal material to the accessory worn by billions today, Danuta Sampson traverses the history of spectacle lenses and their journey to a giant global industry.
Spectacles have evolved from reading stones to advanced vision aids and fashion accessories, with a rich history spanning centuries.1 Initially used for simple magnification in ancient times, spectacles have been transformed due to advancements in materials, optics, craftsmanship, and our understanding of vision. Some experts claim they are history’s fifth most important invention, allowing millions to enjoy good vision despite their native imperfect vision.1 Here, I will briefly describe the optics behind, and the history of, spectacle lenses. The evolution of spectacle lens materials is a fascinating topic in its own right but that’s for another day.
A lens is an optical element that, through the process of refraction (bending of light rays), can converge (positive lens – used to correct hyperopia) or diverge (negative lens – used to correct myopia) a bundle of rays. The term lens originates from the Latin lēns, meaning lentil, the double-convex seed we eat.2 The lens is defined by two refractive surfaces formed from a transparent optical medium (e.g., glass or plastic). The lens surface may have any shape, including a double-convex shape – like a lentil. The lens properties, such as being positive or negative, and its power, depend on its shape and the ratio of the material’s refractive index to the index of the surrounding medium.
AROUND THE 10TH CENTURY, ITALIAN MONKS DEVELOPED THE READING STONE, WHICH WE KNOW TODAY AS A MAGNIFYING GLASS.
Evidence suggests the first lens (known as the Nimrud lens, made of rock crystal) was created in 750-710 BCE in Mesopotamia (now Iraq); however, its purpose remains unknown.3 The idea behind using lenses as a visual aid was initially described in Ptolemy’s Optics (1st century CE) and further advanced by Ibn al-Heitam (Alhazen) in his Book of Optics (10th century CE).1,4 Around the 10th century, Italian monks developed the reading stone, a semi-spherical lens made of rock crystal and quartz, which we know today as a magnifying glass. The first evidence of wearable spectacles was documented in the 13th century in Northern Italy.1,4 It coincides with advancements in glassmaking on the Italian island Murano near Venice and translations of Alhazen’s book into Latin. These early spectacles featured lenses set in frames that rested on the nose, marking a pivotal moment in the history of vision correction.
It wasn’t until the 18th century that the spectacles we recognise today took shape.1 Also then, American Benjamin Franklin proposed the concept of split bifocal lenses, often referred to as a Franklin bifocal.5 These marked a significant advancement in vision correction, offering a practical but sub-optimal solution to seeing distant and near objects using a single pair of eyeglasses.
The 19th century brought further refinements, including toric lenses for astigmatism correction (invented by English astronomer George Airy)6 and improvements in bifocal designs to enhance comfort and functionality. Trifocal lenses followed, aiming to provide correction for intermediate distances, though these early designs suffered from visible segment lines and limited depth of focus.
The 20th century witnessed the development of progressive addition lenses (PALs), offering a seamless transition between different optical powers for clear vision at all distances. Englishman Owen Aves was granted the first patent for PALs in 1907, but he could never produce such lenses due to the manufacturing limitations.7 In the 1960s, the first commercially successful progressive lenses became available thanks to the inventions of France’s Bernard Maitenaz.
The original progressive lenses were made from pre-produced, semi-finished moulds. From about 1980 onwards, multifocal lenses were transformed thanks to the integration of freeform technology. This innovation allowed for custom-designed lenses tailored to the unique needs of each wearer. Freeform technology utilises computer algorithms to create personalised multifocal lens designs based on a patient’s prescription, frame measurements and specific visual habits. However, they have some limitations, including lower effectiveness of the refractive zone and higher peripheral distortion in low-light conditions. In the case of specialised vision needs, the design options afforded by progressive lenses can be limited.
Lens design continues to advance. A recent innovation is the spiral shaped diopter lenses by researchers from Bordeaux in France.8 These lenses are designed to maintain clear focus at various distances and lighting conditions, overcoming some limitations of traditional multifocal lenses.
They use a spiral-shaped design to achieve multiple points of focus, potentially revolutionising multifocal lens technology if it successfully becomes a consumer product.
In conclusion, spectacles have evolved remarkably to become a global accessory worn by billions. Looking forward, research continues to focus on improving lens materials, manufacturing techniques, and optical algorithms to enhance the quality and versatility of spectacles. The “perfect lens” remains an exciting goal, promising further advancements in vision correction and optical technology.
ABOUT THE AUTHOR: Dr Danuta Sampson is a translational researcher and senior lecturer jointly appointed between the Lions Eye Institute and the School of Optometry at the University of Western Australia. She is involved in the global optics and photonics community through engagement with Optica and SPIE – the largest optics and photonics societies globally. She serves as a light science ambassador and supports various committees for Optica and, with SPIE, designs STEM children’s books and educational games/materials.
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References
1.https://www.zeiss.com.au/vision-care/eye-health-and-care/understanding-vision/the-history-of-glasses.html,
2. Wikipedia: Lens
3. https://www.britishmuseum.org/collection/object/W_-90959
4. Rubin M. Spectacles: past, present, and future. Surv Ophthalmol. (1986)
5. Letocha C.E. The invention and early manufacture of bifocals, Surv Ophthalmol. (1990)
6. Levene J.R. Sir George Biddell Airy, F.R.S. (1801-1892) and the discovery and correction of astigmatism, Royal Society (1966),
7. Mesiter D.J. & Fisher S.W. Progress in the spectacle correction of presbyopia. Part 1: Design and development of progressive lenses, Clinical and Experimental Optometry (2008).
8. Galiner L. et al. Spiral diopter: freeform lenses with enhanced multifocal behaviour, Optica (2024).
