Comparison of modified bell retinoscopy (MBR), Nott retinoscopy (NR), and monocular estimate method (MEM). (A–C) correlation between lag measured by MBR and NR, MBR and MEM, and NR and MEM; solid lines indicate line of perfect agreement; dotted lines show linear regression fits. Panels D–F: Bland-Altman plots of inter-method difference in lag plotted against mean lag measurement for MBR compared to NR, MBR compared to MEM, and NR compared to MEM; dotted lines indicated linear regression fits (bias functions).