Table 1.

Example of how to combine effect size and variance of change score of CH and CRF within studies

Study	Outcome (mmHg)	SMILE			LASIK			Effect size (Hedges’ g)	Variance of Hedges’ g	Combined effect size	Correlation between CH and CRF	Combined variance
		Mean	SD	N (eye) at last follow-up	Mean	SD	N (eye) at last follow-up
Alper Agca [38]	CH	−1.94	1.52	30	−1.98	1.5	30	0.03	0.06	−0.07	0.71	0.06
	CRF	−2.96	1.69	30	−2.69	1.44	30	−0.17	0.07
Di Wu [39]	CH	−1.94	0.82	37	−2.34	1.08	34	0.42	0.06	0.48	0.71	0.05
	CRF	−3.59	0.91	37	−4.29	1.6	34	0.54	0.06
Wenjing Wu [40]	CH	−1.86	1.13	75	−2.23	1.33	75	0.3	0.03	0.4	0.71	0.02
	CRF	−3.14	1.06	75	− 3.8	1.53	75	0.5	0.03
Bingjie Wang [41]	CH	−2.55	1.44	50	− 2.53	1.38	56	−0.01	0.04	0.4	0.71	0.03
	CRF	−2.24	1.29	50	−3.33	1.34	56	0.82	0.04

Abbreviation: CH corneal hysteresis, CRF corneal resistance factor, LASIK laser-assisted in situ keratomileusis, SD standard deviation, SMILE small incision lenticule extraction