Biology class 12 assignment neet level practise chapter wise
Lens Shapes
1. LENS SHAPES
Fakhruddin S. Barodawala M. Optom,
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2. • Most ancient shape
• Due to round edge, nasal edge cannot be easily
determined so care must be taken while fitting that the
centration is in correct direction
• Not advisable for toric Rx
3. • Elliptical
• Produced by cutting through a circular rod in any plane
oblique to the axis
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4. • Lower half is elliptical shape with same horizontal
diameter
• Important part of evolution of modern lens shape
because it was the first step towards recognition of both
functional and ancient wear
• Field of view is larger
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5. • On closing of eye the FOV is not symmetrical
• Nasal side being much more restricted than temporal
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6. • These follow both contour of the face in the region of the
eye and approximately the contour of the eyes field of
vision
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7. • Different shapes and sizes
• Have more or more than four recognizable defined sides
of shallow curvature joined by areas of shorter radium
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8. • Triangular characterized by a nasal cut away and
pounced fullness in the lower temporal quadrant
• Not advisable for progressive and bifocal lens wear as
the reading portion may cut
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9. • Only near correction
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