Table 4

Correlations of best Snellen corrected visual acuity (BCVA), mean deviation (MD) and central foveal thickness (CFT) with disease duration in patients with different types of USH2A mutations

	M+M		M+SNFO		SNFO+SNFO
	r	P value	r	P value	r	P value
BCVA versus duration	−0.574	<0.001	−0.284	0.001	−0.528	<0.001
−≤10 years	−0.433	0.025	−0.444	0.012	−0.684	0.031
−10 to 20 years	−0.152	0.338	−0.339	0.045	−0.132	0.327
−>20 years	−0.384	0.005	−0.002	0.493	−0.038	0.436
MD versus duration	−0.315	0.027	−0.245	0.024	−0.239	0.155
−≤10 years	−0.300	0.171	−0.030	0.454	−0.120	0.411
−10 to 20 years	−0.894	0.053	−0.352	0.108	−0.894	0.053
−>20 years	−0.525	0.006	−0.220	0.106	−0.303	0.197
CFT versus duration	−0.177	0.154	−0.455	<0.001	−0.01	0.481
−≤10 years	−0.773	−0.004	−0.04	0.437	−0.894	0.053
−10 to 20 years	−0.051	0.452	−0.013	0.480	−0.049	0.446
−>20 years	−0.673	0.002	−0.540	0.007	−0.278	0.219

BCVA, best Snellen corrected visual acuity; CFT, center foveal thickness; M, missense; MD, mean deviation; RP, retinitis pigmentosa; SNFO, splice-site, nonsense, frameshift, or others (readthrough, gross deletions and small indels); USH2, Usher syndrome type IIa.