Refraction After Intraocular Lens Implantation: Results with a Computerized System for Ultrasonic Biometry and for Implant Lens Power Calculation

Prediction of the effective postoperative (intraocular lens) anterior chamber depth

“…21,22 If not corrected for the axial length dependence, the IOL power calculation formula becomes biased and gives erroneous predictions in long and short eyes. 23,24 The preoperative ACD has also been described as a predictor for some time, 22,25,26 and is included in the ACD algorithms of several modern IOL power calculation formulas. An example is the Haigis formula, 7 which uses the following regression approach to the ACD prediction:…”

Intraocular Lens Power Calculations: The Optimal Approach

“…A second fact is the need to employ data in the theoretical formulas that are not known preoperatively. When one uses the preoperative axial length, corneal curvature and a standard depth for the anterior chamber, one ignores the fact that the postoperative axial length might be shorter [10,11] or longer [12]; the postopera tive cornea flatter [3,13,14] orsteeper [ll, 15] and the anterior chamber will not always have the assumed standard depth [3,11,13,16], All these parameters depend on the geometry of the eyeball, as well as on the experience and skill of the implant surgeon. Finally systematic errors may be caused by the assumptions on the effective thickness of the retina [3.11.14,15] and the sound veloc ity of the media [14], As long as no communis opinio is at tained on these matters, the alternative for mula suggested by Sanders, Retilaff and Kraff:…”