phakometer

Optical instrument designed to measure the radii of curvature of the crystalline lens. The method is based on a comparison of the sizes of the third h′₃ and fourth h₄′ Purkinje images (typically determined by photography) with that of the first image h′₁, that is the anterior corneal surface, the characteristics of which are easily measured. The radius of curvature of, say the fourth Purkinje image r′₄ can be calculated using the approximate equationr′₄ = r₁ (h₄′/h′₁)where r₁ is the radius of curvature of the front surface of the cornea. If the test object is near the eye a correction factor is necessary. See Purkinje-Sanson image; ophthalmophakometer; phacoscope.

单词	phakometer
释义	phakometer phakometer Optical instrument designed to measure the radii of curvature of the crystalline lens. The method is based on a comparison of the sizes of the third h′₃ and fourth h₄′ Purkinje images (typically determined by photography) with that of the first image h′₁, that is the anterior corneal surface, the characteristics of which are easily measured. The radius of curvature of, say the fourth Purkinje image r′₄ can be calculated using the approximate equationr′₄ = r₁ (h₄′/h′₁)where r₁ is the radius of curvature of the front surface of the cornea. If the test object is near the eye a correction factor is necessary. See Purkinje-Sanson image; ophthalmophakometer; phacoscope.
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