Intraocular Lens Power Formula Selection Using Support Vector Machines

In cataract surgery, the defected lens is replaced with an artificial intraocularlens (IOL). The refraction power of this lens is specified by ophthalmologistsbefore the surgery. There are different formulas that propose the IOL powerbased on corneal power and axial length. Six common formulas is used in thisstudy and the one which minimizes the postoperative error for a specific patienthave to be selected. Refraction is measured three times at most, during six month after surgeryand the best result is considered as postoperative refraction for each patient. Asupport vector machine (SVM) is used to classify the data to two groups based onaxial length and corneal power. Each class needs a formula with a specific tendencytoward stronger or weaker IOL lenses according to the feature vector. Experimental tests lead to a nearly diagonal confusion matrix whichsupports the performance of the proposed method strongly. Mean Absolute Error(MAE) is 0.47 which shows 6% decrease in postoperative refraction error comparedto the best reported result. In calculating IOL power, we expect stronger IOL powers for eyeshaving shorter axial length or weaker corneal power. In the contrary, a weaker IOLpower is expected for longer axial length and stronger corneal power. But experimentalresults show that for the first group, formulas proposing weaker powers winthe race for decreased postoperative refraction error while for the second group,formulas leading to stronger powers perform better. This shows that these formulasoverestimate and underestimate for marginal cases.