Table 2. The mean numerical errors, mean absolute errors, and median absolute errors of the three calculation methods tested (n=32).

Formula/method	Refraction prediction error (D)
	Numerical			Absolute
	Mean ± SD	Range		Mean ± SD	Median	Range
Haigis-L	−0.65±0.68	−2.29, 0.81		0.74±0.58	0.57	0.04, 2.29
Barrett True-K	−0.39±0.64	−2.82, 0.89		0.53±0.52	0.40	0.01, 2.82
Shammas-PL	−0.46±0.69	−3.02, 0.91		0.59±0.59	0.49	0.00, 3.02