| 1947 |
Kevin Tuohy first applies
for a patent for a corneal diameter lens. This is fitted flatter
than the cornea, has a constant overall diameter of 11.50 mm, a flange (or
peripheral ) width of 1.5 mm and a central thickness of 0.25-0.35 mm. |
|
| 1947 |
Heinrich Wohlk
between 1946 and 1948, independent of Tuohy, develops a corneal diameter lens fitted flatter
than the corneal curvature. |
|
| 1952 |
The Microlens is launched in England by Frank
Dickinson; in Germany by Sohnges;
and in the USA by Jack Neill.
The single curve design is fitted flatter than the cornea, has a constant
diameter of 9.50 mm and a thickness of 0.20 mm for an afocal lens. |
|
| 1957 |
Norman Bier introduces the Contour lens which
consists of a relatively small optic zone surrounded by a wide peripheral
curve between 0.40 and 0.70 mm flatter than the central radius. It
is fitted in corneal alignment with a standard diameter of 9.65 mm. (Tear
lens diagrams from The Contact Lens Manual, Andrew Gasson and
Judith Morris, 2003). |
|
| 1964 |
Freddie Burnett Hodd
designs the Hodd Tapered Lens which has a series of carefully calculated peripheral curves.
Fitting sets are available through Nissel. |
|
| 1966 |
Corneal lenses with offset peripheries are designed
by Montague Ruben, head of the Contact Lens department at
Moorfields, and manufactured
by Omega Contact Lenses. |
|
| 1967 |
Nissel introduces
an aspheric design based on the work of Volk
in the USA. It consists of a central aspheric portion with
a 7.80 mm diameter, two spherical zones at diameters of 8.40 mm and 8.80
mm, and a flat edge bevel to assist tear flow. |
|
| 1967 |
Penrhyn Thomas in Australia introduces the Conoid lens
which consists of a steep central optic with tangential peripheral curve.
(Illustration from "Conoid Contact Lenses,
Penrhyn Thomas, 1967).
|
|
| 1966 |
Janet Stone designs a series of lenses with Constant
Axial Edge Lift. These are multicurves which for a given
overall diameter have the same edge lift throughout the range of radii.
(Tear lens diagrams from The Contact Lens Manual,
Andrew Gasson and Judith Morris, 2003). |
|
| HARD
GAS-PERMEABLE LENSES |
| 1975 |
The original Boston lens material is developed.
Following further research and development, it gains FDA approval as Boston
II in 1982. |
|
| 1977 |
Cellulose acetate butyrate (CAB) is introduced as an
early hard gas-permeable material for corneal lenses.
Compression moulded
lenses such as Hartflex or the later Conflex from Wohlk,
or Persecon from Titmus-Eurocon give dimensional stability. |
|
| 1979 |
Menicon in Japan introduce the Menicon O2
silicone acrylate lens. This is later followed by Menicon SP
and Menicon EX in 1986. |
|
| 1980 |
Polycon, an early silicone acrylate gas-permeable material,
is introduced by Syntex. This is followed by the improved Polycon II
in 1982. |
|
| 1980 |
Irving Fatt
devises his Dk system for the measurement of oxygen permeability using a
polaragraphic cell. (Illustration
courtesy the Contact Lens Collection of the College of Optometrists). |
|
| 1987 |
The Diffrax bifocal is introduced by Pilkington in either
Polycon II or Fluorocon 60. The lens is based on the principle of a
central area of diffraction providing near and distance retinal
images. (Illustration courtesy the Contact Lens
Collection of the College of Optometrists). |
|