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Past
The history of contact lenses provides ample reasons to be optimistic
about their future. From hard glass contacts with their host of
problems to disposable silicon-gel extended wears with their far
fewer problems has been, largely, one long and successful journey.
Problems, however, still remain. And so long there are problems,
further development is always possible.
Present
Modern lenses made from high oxygen permeable material have improved
lens quality many times over. They have excellent vision clarity,
considerably reduced eye problems and are much more comfortable
to wear. Today disposable extended wears represent the latest
in contact lens technology. However, 26% of hydrogel extended
contact wearers and 18% of RGP wearers still have eye complications.
Future
Further lens development must go beyond the disposable extended
wear technology. Many believe that the main focus should be on
developing material with still higher oxygen permeability since
oxygen deprivation of the cornea is the root cause of many disorders.
Furthermore, the material should be biocompatible and the lenses
should have improved designs to deliver good vision clarity with
fewer or almost no problems.
At the same time the consumer demands further increase in the
period of extended wear. Such one sided developments conflict
with the safety demands of the eye practitioners. Obviously a
judicious balance will have to be struck
Future trends in contact lenses
Improved performance of contact lenses rests on their quality
attribute. These are:
- Vision clarity
- Comfort
- Absence of infections
- Absence of deposits
Higher are these quality attributes better will be the performance
of the lens.
These attributes and thereby lens performance can be improved
by:
- Improved materials
- Improved surface treatment
- Improved design
These are big technological challenges but not insurmountable
ones. Hopefully they will be overcome sometime in the not too
distant future.
Improved material
There are presently two main unresolved areas of concern. The
first one is about people with myopia, presbyopia and astigmatism
who make up more than half the lens wearing population. To correct
these disorders thicker lenses are needed. Thicker lenses are
problematic as they allow less oxygen to flow through them compared
to thin lenses. The other problem is the closed eye lid which
during sleep becomes an additional barrier to the flow of oxygen
to the cornea.
Many see the solution to these problems in using lenses with
still higher oxygen permeability, minimal water loss and deposit
resistance. Another solution could be daily wear extended lenses
which are replaced regularly.
Silicon-hydrogel lenses with relatively higher oxygen permeability
than hydrogel has a remarkable property. Higher water content
in silicon-hydrogel improves its oxygen permeability unlike
in hydrogel where higher water content reduces the oxygen permeability.
The discomfort felt with RGP lenses may be reduced by using a
more flexible material with an optimum design. Lenses made with
such a silicon-hydrogel variety have been shown to conform more
easily to the corneal shape.
Studies have shown that silicon hydrogen lens accumulate less
protein and other deposits. Deposits should cease to be a problem
if additionally lenses are regularly replaced and cleaned. Studies
have also shown a significant reduction in the common ‘Dry
eye’ problem in those wearing silicon hydrogel lenses.
Overall silicon hydrogel lenses have shown better performance
and provide more comfort. All evidence points to silicon hydrogel
as the material of the future.
Improved surface treatment
The high oxygen permeability of silicon-hydrogel also creates
some problems. The surface treatment in silicon hydrogel lens
makes it wettable and reduces the affinity for some protein deposits.
But it increases the affinity for some kind of denatured deposits.
Although the incidence is only 5% the problem must be resolved
in the future.
Eye blinking is beneficial as it increases the tear amount which
cleans the eye surface. But lenses reduce the tear volume. It
is as yet a moot point whether surface treatment could improve
the tear volume.
Improved design
Improved lens design with high oxygen permeable materials is expected
to correct a broader range of refractive disorders. Improved
lens designs should produce RGP lenses more comfortable in the
initial period and lenses which reshape the astigmatic cornea
better. Better designed lens should also lead to less aberration
and better vision.
Lens care
Finally, no matter how advanced the lenses become, lens care
with its strict cleaning and disinfecting regimen will always
be needed. Used as they are, in contact with the eyes, it is difficult
to imagine a future scenario where cleaning will not be needed.
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