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P. 50
40 Ophthalmic Lenses
Lensometer can also be used to determine the lens power of an astigmatic
lens. The procedure is as under:
• Place the lens on the lens stage and start from zero.
• Focus the target image by rotating the dioptre power knob.
• Read the dioptre power scale when the target image is cleared. This is
taken as either plano for a plano-cylinder lens or spherical for a toric
lens.
• Now focus the target for other meridian by rotating the knob.
• The difference between the second absolute value and the first is taken
as cylinder.
• Align the cross line with the second focused point by rotating the axis
wheel. The angle of the indicator shows the axis.
