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What is the notation for astigmatism?

April 26, 2017astigmatism notation

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What is the notation for astigmatism?

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Astigmatism is measured in cylindrical diopters. Three numbers are needed. The first number is the power of a spherical lens. The second is the power of cylindrical lens and the last number is the principal meridian in degrees for that lens. Facing a patient: 0 degree or 180 degree is horizontal, 90 degree is vertical, 45 is up right to down left, and 135 degree is up left to down right. Optometrist usualy use “minus” notation eg +2.25 -0.75 x 175 and ophthalmologist use “plus” notation eg +2.25 +0.75 x 5 These are the same measurement. so is -1.00 +1.00 x 135 and -1.00 -1.00 x 45 The average astigmatic usually has the horizontal meridian flatter than the vertical meridian.