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82 Ophthalmic Lenses

Reduced Migraines: Patient who experiences migraines may be
hypersensitive to the visual stimuli. Colour filters can reduce symptoms
caused by these stimuli. The choice of lens colour may also be an important
factor to reduce migraines. In one study, children who wore lenses with
either pink or a blue tint experience migraines less frequently after 1 month.
At 4 months, however children wearing only pink tinted lens continued to
experience migraines less frequently.
Reading Comfort and Performance: Tinted lenses may filter out certain
light frequencies and reduce the amount of information the eyes absorb.
Some researchers believe that by reducing the amount of information,
the brain can process better what the eyes see. Another study of children
and adults with learning disabilities showed that the rate of reading was
significantly faster in the subjects who read with glasses that had a
coloured overlay compared with those who read with glasses without a
colour overlay. Research by Optometrist Mr. Harold A. Solan from New
York, has demonstrated that blue light filters are superior to the other
colour filters for this purpose. It caused improvement in the number of
fixations and regression and rate of reading in children with learning
disabilities.
Driving Factors: Lenses for driving must not be too dark, as they reduce
visual acuity. It is essential to offer protection to the eyes while driving in
order to see better, react quickly to dangerous conditions and improve
safety. A brown tinted lens is ideal for drivers for day time driving as
they reduce the transmission of blue light. But it is too dark to use in the
night. Night driving lenses would typically have a yellow tint or amber
tint with antireflection coating which may improve contrast and reduce
glare.
There may be a possibility that the subject may not be very comfortable
with any tint and he rejects all the colours. But the normal requirements
of protections still apply – everyone should protect their eyes in bright
sunlight. In practice, a neutral density grey filter would be used by this
group. Contrarily, if all the colours are equally liked, then the tint can be
chosen on optical principles, say when required for sunglass, a brown
tint which has UV absorption and contrast enhancing properties would
be better.

BLUE LIGHT HAZARDS
We know that sunlight is divided into various families by wavelength of
light: ultraviolet, visible light and infrared and others. In the atmosphere,
the first natural barrier encountered by the sun’s radiation is ozone layer.
Ozone minimizes the effect of ultraviolet radiations. Infrared radiation is
filtered out by water droplets in suspension in the lower levels of