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100 Ophthalmic Lenses

However, today’s fact is the aphakic lenses are not much used any more.
Implants are almost universal and they allow the use of ordinary correction.
A great number of patients go for contact lenses. They need glasses for part
time use. A few still have true aphakia, which may take advantage of these
lenses.

CHECKING LENS POWER IN ASPHERIC LENS
The lens power in case of aspheric lenses can be measured on the focimeter
so that it is aligned through the geometric centre or middle of aspheric side
of the lens. In this area of the lens, the correct power as per the prescription
can be seen. As we move away from the geometric centre of aspheric surface,
the prescription alters- incline with the way the lens surface changes power.
The aspheric lens designer specifies a portion, which will be the central
region of aspheric side of the lens to be assured of 100% full prescription;
the rest of the lens will have a different prescription. The size of this portion
depends on the formula, the designer used to formulate the shape of the
curves.

DISPENSING TIPS
Aspheric lenses represent the ultimate in optics . Using the aspheric curves
in a lens produces two benefits: better vision and improved cosmetics. This
immediately places the lens into the premium category, providing better
profits for every one. This imposes an additional responsibility on dispenser
because aspheric can be less forgiving than conventional lenses and requires
more precise positioning by the dispenser. A poorly fitted aspheric lens

Fig. 9.10: Aspheric fitting guide