For high corneal cylinder nomograms start relative to K as:

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Multiple Choice

For high corneal cylinder nomograms start relative to K as:

Explanation:
When corneal cylinder is high, the toric correction on a gas-permeable back surface must engage the eye at the meridian with the greatest curvature. Start the nomogram relative to the steep keratometric meridian, because the steeper meridian represents where the eye is most curved and where the astigmatic error is largest. Aligning the lens’s toricity to that steeper meridian helps neutralize the cylinder and promotes better fit, centration, and stability. Beginning relative to the flatter meridian would under-correct the steep meridian, and starting on or off the keratometry without targeting the steep axis wouldn’t provide the necessary correction.

When corneal cylinder is high, the toric correction on a gas-permeable back surface must engage the eye at the meridian with the greatest curvature. Start the nomogram relative to the steep keratometric meridian, because the steeper meridian represents where the eye is most curved and where the astigmatic error is largest. Aligning the lens’s toricity to that steeper meridian helps neutralize the cylinder and promotes better fit, centration, and stability. Beginning relative to the flatter meridian would under-correct the steep meridian, and starting on or off the keratometry without targeting the steep axis wouldn’t provide the necessary correction.

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