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190 Ophthalmic Lenses

Fig. 13.3: High surface wetting angle

Fig. 13.4: Water droplets on a hydrophobic coating

than wetting and then drying on the surface. It can be applied simply by
dipping process. Baking after dipping enhances the life. It can also be
applied in the vacuum chamber as the final stage of the multi-layer anti-
reflection coating process.

ANTI-FOG COATING
The potential for eye injuries in sports and battlefield has increased over
the years. Fogging of spectacle lenses can occur from a combination of body
heat and environmental factors which can result in blur vision from sweat
beads streaming down the lenses. A film of anti-fog coating can be applied
on the back surface of the lens which is compatible with hard coating to
protect the lens from being fogged. A good anti-fogging treatment has not
only initial anti-fogging properties but also good anti-fogging retainability.
At times anti-fogging lens cleaning solutions have been used in the form of
sprays, the effect of the same has yet to be studied.