Table 3.

Preoperative standard and custom variables derived from the dynamic bidirectional applanation device.

Variable*	Femto LASIK	PRK	P Value
A1
Mean ± SD	724.6 ± 119.1	682.5 ± 123.7	.0002†
95% CI	701.45, 747.76	627.3, 687.2
A2
Mean ± SD	572.6 ± 117.7	537.1 ± 117.9	.02
95% CI	549.7, 595.5	508.6, 565.6
Applanation peak difference
Mean ± SD	−166.1 ± 104.7	−179.1 ± 145.5	.2
95% CI	−185.0, −147.3	−238.0, −121.4
Concavity min
Mean ± SD	42.4 ± 0.5	42.4 ± 0.5	.6
95% CI	42.3, 42.5	42.2, 42.5
Concavity mean
Mean ± SD	151.2 ± 23.9	135.7 ± 22.2	<.0001†
95% CI	146.5, 155.9	130.3, 141.1
CRF (mm Hg)
Mean ± SD	10.6 ± 1.9	9.9 ± 2.2	.0007†
95% CI	10.2, 10.9	9.3, 10.4
CH (mm Hg)
Mean ± SD	10.8 ± 1.7	9.9 ± 1.8	.0003†
95% CI	10.4, 11.1	9.4, 10.4
P1P2Avg
Mean ± SD	181.52 ± 26.31	181.9 ± 32.5	.9
95% CI	176.41, 186.64	174.0, 189.8
P max
Mean ± SD	426.53 ± 38.95	421.8 ± 48.3	.4
95% CI	418.96, 434.11	410.1, 433.60
Concavity duration (ms)
Mean ± SD	10.85 ± 0.60	10.79 ± 0.64	.6
95% CI	10.73, 10.98	10.64, 10.95
Concavity time (ms)
Mean ± SD	12.70 ± 0.06	12.70 ± 0.07	.3
95% CI	12.69, 12.72	12.68, 12.71
Lag time (ms)
Mean ± SD	0.22 ± 0.21	0.29 ± 0.37	.7
95% CI	0.18, 0.27	0.14, 0.45
Applanation onset time (ms)
Mean ± SD	8.10 ± 0.51	8.06 ± 0.62	.5
95% CI	8.00, 8.20	7.91, 8.21
Slope up (ms−1)
Mean ± SD	40.04 ± 10.25	40.15 ± 12.47	.6
95% CI	38.04, 42.03	37.13, 43.17
Slope down (ms−1)
Mean ± SD	−43.79 ± 20.99	−42.33 ± 26.33	.1
95% CI	−47.87, −39.70	−48.71, −35.96
HLA × 103
Mean ± SD	116.10 ± 23.03	102.9 ± 21.4	<.0001†
95% CI	111.62, 120.59	97.7, 108.1
Impulse × 103
Mean ± SD	4.60 ± 3.68	4.56 ± 0.45	.4
95% CI	4.52, 4.67	4.45, 4.67

CI = confidence interval; Femto LASIK = femtosecond laser–assisted laser in situ keratomileusis; ms = millisecond; PRK = photorefractive keratectomy

^*See Table 1 for definitions of variables.

^†Statistically significant