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166 Ophthalmic Lenses

Visual Needs
Information about the patients visual needs enables the practitioner to
understand whether the progressive addition lenses will meet the patient
expectations or not. Those who require a larger field of view can
immediately be eliminated from the consideration. An avid user of
computers will be benefited more by occupational lenses rather than a
progressive addition lenses. The progressive addition lenses for him may
be prescribed as a supplement for general use. Most commonly used near
working distance also influence the selection criteria. A patient who
invariably works at shorter and middle distance will be a happy user of
progressive addition lenses, whereas a constant user of shorter reading,
working distance will prefer to have bifocal lenses. Relative use for distance/
near visual zones also sometimes influences the criteria. Myopes who
depend more on distance visual zone have always been more successful
user of progressive lenses.

Refractive Status
Progressive addition lenses should be avoided for that refraction which
may induce vertical prism between the eyes including different refraction
between the eyes by more than 2.00 D in spherical power or more than
2.00D in effective cylinder power especially in the vertical meridian
(horizontal axis).

IDEAL FRAME SELECTION FOR PROGRESSIVE ADDITION LENS
The ideal frame selection is an important criterion for the successful
dispensing of progressive addition lenses. Many a times it has been seen
that in spite of having perfect refraction and fitting, the patient is not the
happy user of the progressive lenses and the reason established is not other
than poor frame selection. The frame should be selected in such a manner
so as to cover adequate facial width and also minimizes the vertex distance.
Metal frames with adjustment nose pad are more suitable than plastic
frames as the fitting height can be adjusted, if required, using the nose
pads. While selecting the suitable frame for an individual who is opting
for progressive addition lens, the following two factors must be taken into
consideration -

Shape of the Frames

Square and panto shapes as shown in the Figure are the most suitable shapes
for the progressive addition lenses. Steep rectangular shapes extending
beyond the temporal bone of the face may not be suitable. Another
important factor in frame selection is ensuring that the shape of the frame