title: Axial length measurement and its relation to intraocular lens power calculations.
abstract: The axial length was measured in five hundred consecutive cases using the Kretz 7200 MA ultrasound unit and an immersion technique. The reproducibility of the measurements was within +/- 0.2 mm when performed manually, and within +/- 0.05 mm when performed electronically. Intraocular lens power calculations were performed using a modification of Colenbrander's formula. We predicted within + 1 diopter in 78.8% of the cases. The accuracy was up to 83% when the axial length ranged between 23.0 and 25.0 mm. Stronger power lenses were implanted in shorter eyes and weaker power lenses in longer eyes, necessitating the use of a fudge factor. Surgeons using an immersion technique for axial length measurements should use formulas yielding stronger power lenses, such as Binkhorst's formula or our modification of Colenbrander's formula, with a fudge factor for short and long eyes.
mesh_terms: D001699:Biometry / Q000295:instrumentation / Q000379:methods; D005123:Eye / Q000033:anatomy & histology*; D006801:Humans; D007910:Lenses, Intraocular / Q000592:standards*; D055095:Optics and Photonics; D014465:Ultrasonics / Q000295:instrumentation