Keratometry - Lecture notes 6 PDF

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Keratometry...

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Keratometry Procedure 

As per convention we do the right eye first. Roughly align the px such that the mires are reflected in the px’s cornea.

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Instruct the px to look at their own eye, it can be viewed by reflection in the barrel.

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Focus the mires and ensure that the cross is centred in the lowest right-hand circle.

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Locate the two meridians (look at the “plusses” and “minuses”).

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Rotate the barrel such that the “plusses” are aligning and forming one horizontal line.

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Then move the horizontal (right barrel) and vertical lines (left barrel), by turning the right and left barrels, such that they are overlapping. Forming one plus and one minus.

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The cross must still be centred in the lower right-hand circle.

Recording Eg: 42.00D @180 / 43.00D @90 Analysis 

The difference between the dioptrical values is the corneal astigmatism.

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More power in the vertical=WTR, more power in the horizontal=ATR. It is irregular if the axes are not 90 degrees apart.

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Remember that the power is 90 degrees to the axis. If the axis is 90 then the power is at 180. The prescription most likely to be found when verting the spectacles would be 180

Keratoconus Rating 

Mild < 45D in both meridians

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Moderate 45-42D in both meridians

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Advanced >52D in both meridians

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Severe >62D in both meridians

Base Curve Calculations BC = K1+K2/2 +0.9mm...