Table 2.

Comparison of masticatory and cervical muscle thickness and activity between groups.

	Myopia Subject (n = 21)		Subject without Refractive Error (n = 19)		Test		p
	Mean	SD	Mean	SD
TA RestR (mm)	13.18	1.78	12.20	1.48	t	1.90	0.06
TA ClenchR (mm)	13.86	1.82	12.77	1.49	t	2.06	0.04 * ES = 0.60
MM RestR (mm)	11.94	2.18	12.42	1.51	t	−0.81	0.42
MM ClenchR (mm)	13.48	2.39	13.52	1.58	t	−0.05	0.96
DA RestR (mm)	6.55	0.63	6.67	0.81	z	−0.33	0.75
DA ClenchR (mm)	6.47	0.55	6.67	0.83	z	−0.64	0.52
SCM RestR (mm)	9.36	1.37	10.25	1.37	t	−2.05	0.04 * ES = 0.65
SCM ClenchR (mm)	9.37	1.31	10.26	1.42	t	−2.06	0.04 * ES = 0.69
TAR (μV)	1.80	0.84	2.05	1.99	z	0.66	0.51
MMR (μV)	2.53	1.67	2.18	1.31	z	0.58	0.56
DAR (μV)	1.30	0.37	1.16	0.39	z	−0.96	0.34
SCMR (μV)	1.70	0.75	1.93	0.76	z	1.57	0.12
TA RestL (mm)	12.25	1.78	12.20	1.90	z	−0.03	0.98
TA ClenchL (mm)	12.88	1.87	12.80	2.00	z	0.22	0.83
MM RestL (mm)	12.43	2.30	12.69	1.55	z	−1.02	0.31
MM ClenchL (mm)	13.78	2.40	13.75	1.53	z	−0.03	0.98
DA RestL (mm)	6.70	0.97	6.56	0.75	t	0.37	0.71
DA ClenchL (mm)	6.61	0.98	6.58	0.74	t	0.09	0.93
SCM RestL (mm)	9.51	1.55	10.00	1.14	t	−1.12	0.27
SCM ClenchL (mm)	9.56	1.55	9.99	1.15	t	−1.00	0.33
TAL (μV)	1.90	0.93	2.30	1.80	z	−0.35	0.72
MML (μV)	2.01	1.09	2.40	1.65	z	−1.14	0.26
DAL (μV)	1.40	0.49	1.33	0.45	z	−0.22	0.83
SCML (μV)	1.71	0.75	1.63	0.54	z	0.50	0.62

TA—the temporalis anterior; MM—the superficial part of the masseter muscle; SCM—the middle part of the sternocleidomastoid muscle; DA—the anterior belly of the digastric muscle; _R—right site; _L—left site; _μV—microvolt; _mm—millimeters; Rest—ultrasound muscles examination in the relaxed mandible position with slight contact between opposing teeth; Clench—ultrasound muscles examination in the maximum voluntary clenching; t—student t-test; z—Mann–Whitney U test; ES—effect size; *—significant difference.