Ultrasonic biometry for lens implantation: analysis of systematic errors

Summary

Systematic errors in the echographic biometry of the eye are discussed: correction applied to the thickness of the retina, deviation of the visual axis from the optical axis of the eye and the errors arising from the employment of a single average ultrasound velocity in the eye media. The effects of the systematic errors on the results of the optical calculation of the emmetropizing power of implant lenses are investigated. The effects on the SRK calculation method are indicated and appear to be of the same order of magnitude as those on the optical method. The optical method yields unbiased lenspowers, whereas the SRK method produces refraction errors which systematically depend on the implant lens power.