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[Relationship between lens power in refraction]
M Bechmann1, M Schaumberger, C L Schönfeld
1Augenklinik der Ludwig-Maximilians-Universität München. Martin.Bechmann@ak-i.med.uni-muenchen.de
Background:
To achieve emmetropia, several components such as the cornea and lens power, and axial length have to be coordinated. Until now, not much is known about the influence of these factors on each other.
Methods:
A total of 66 healthy subjects were enrolled in this study. Ocular dimensions including anterior chamber depth, lens thickness, vitreous chamber depth, and axial length were measured by A-scan ultrasonography. Corneal radius and corneal refractive power were determined by ophthalmometry. The equivalent lens power was calculated by a method based on the Gullstrand schematic eye.
Results:
As expected, a good correlation was found to exist between refraction and axial length. Lens power was independent of refraction, but in emmetropic eyes a good correlation between lens power and axial length could be found. Higher axial length was related to lower values of lens power and vice versa.
Conclusion:
In emmetropic eyes, deviation of axial length seems to be compensated by lens power and if this mechanism does not function, ametropia results.