Rigid Gas Permeable Lenses

Irving Fatt (1920-1996)

1979 Rigid gas permeable (RGP) contact lenses were made available as an alternative to the soft lens. The Polycon lens was launched by Syntex in 1980. The rationale for producing gas-permeable materials was provided by an American chemist resident in London, Irving Fatt. He carried out some ground-breaking studies into oxygen tension and permeability with Jennifer Chaston, FCOptom at St Thomas' Hospital and Judith Morris, FCOptom at Moorfields. The original polaragraphic cell (c.1976) used in this work as an oxygen permeability gauge is now in the museum.

This is the original polaragraphic cell used by Irving Fatt and Judith Morris for the early measurement of oxygen permeabiliites of materials (DK values).

To the right is a fitting set of ten 'Excel O2' hard gas permeable corneal contact lenses dating from the early 1980s by G. Nissel & Co.

The Excel O2 was an early second generation GP lens noted within the profession for its excellent wettability (making it, therefore, very comfortable to wear). Its standardised parameters made it suitable as a stock lens in busy practices.

G. Nissel & Co was founded by the brother-in-law to Josef Dallos in 1946 and started making contact lenses in PMMA as soon as that material became available after the war. George Nissel, born in Transylvania in 1913, nearly went to America in 1942 as the evidence from correspondence held in the museum shows, but he elected instead to become a British citizen, opening factories in London (1946-1972) and Hemel Hempstead (from 1958).

George Nissel

(1913-1982)

In 1963 Nissel was probably the first company to produce soft lenses outside of Czechoslovakia. Nissel used lathing and was asked by Otto Wichterle to find a suitable way of polishing hydrophilic lenses. These attempts were discontinued in 1968 however, because of inconsistencies in the materials then available.

The 'Hartflex' gas permeable contact lens fitting set from Wöhlk-Contact-Linsen (1977) was the first type of hard gas permeable lens manufactured by compression moulding from cellulose acetate butyrate (CAB) and launched in the UK during 1977. It was based on the Parabolar and Parabolett designs which had been produced in PMMA.

(Polymethylmethacrylate was not a purpose-designed lens material and thus had had the disadvantage of negligible oxygen transmission and a relatively hydrophobic surface).

Glossary:

CAB - cellulose acetate butyrate. CAB had superior wetting characteristics, was permeable to oxygen and less brittle, with greater thermal conductivity. Its thermoplastic nature made it suitable for either moulding or lathe cutting. CAB materials were first made available for contact lens use in 1973. The first CAB lens was the Persecon (1977). Frank Dickinson found that problem patients could wear CAB lenses all day and wrote an article in 1977 entitled 'There's a lot of mileage in hard lenses yet'.

1983 Tinted RGP lenses made available.

1986 Extended wear RGP lenses made available.

1987 Diffrax - the first diffractive RGP bifocal contact lens, designed by Dr Michael Freeman of London (author of later editions of Fincham's Optics): Unlike conventional bifocal designs they provided distance and near powers created by a centrally located diffractive zone on the back surface of the lens. Since the diffractive design involved two focal powers giving two focal points, independent of pupil size, lighting conditions would not affect the image. The lens was available in Polycon II or Fluorocon 60 material. It could be fitted in a similar way to a single vision gas permeable lens.

The College of Optometrists

Rigid Gas Permeable Lenses