Table 3

Test–retest reliability statistics of the VILL-33 subscales per AMD stage

OveralliAMDNo AMDEarly AMDLate AMD
n=289n=167n=53n=28n=41
VILL reading and accessing informationICC
(95% CI)		0.920
(0.900 to 0.936)		0.868
(0.825 to 0.901)		0.736
(0.584 to 0.838)		0.958
(0.912 to 0.980)		0.878
(0.783 to 0.933)
CoR1.91.72.40.52.2
Deming intercept
(95% CI)		−0.14
(−0.29 to 0.01)		−0.18
(−0.37 to 0.01)		−0.23
(−0.82 to 0.37)		−0.25
(−0.57 to 0.07)		−0.22
(−0.65 to 0.21)
Deming slope
(95% CI)		0.93
(0.87 to 0.98)*		0.93
(0.85 to 1.01)		0.97
(0.77 to 1.18)		0.95
(0.89 to 1.02)		0.87
(0.68 to 1.06)
VILL mobility and safetyICC
(95% CI)		0.929
(0.911 to 0.943)		0.904
(0.872 to 0.928)		0.800
(0.677 to 0.879)		0.974
(0.944 to 0.988)		0.932
(0.876 to 0.963)
CoR1.81.72.40.91.7
Deming intercept
(95% CI)		0.04
(−0.08 to 0.17)		−0.10
(−0.31 to 0.11)		0.07
(−0.52 to 0.66)		0.19
(−0.15 to 0.53)		0.05
(−0.21 to 0.30)
Deming slope
(95% CI)		0.94
(0.89 to 0.99)*		0.97
(0.88 to 1.06)		0.99
(0.75 to 1.23)		0.90
(0.82 to 0.97)*		0.88
(0.78 to 0.97)*
VILL emotional well-being
 
 
 		ICC
(95% CI)		0.822
(0.78 to 0.856)		0.791
(0.727 to 0.842)		0.632
(0.44 to 0.77)		0.895
(0.788 to 0.95)		0.769
(0.608 to 0.869)
CoR5.04.54.43.66.3
Deming intercept
(95% CI)		0.06
(−0.19 to 0.31)		0.14
(−0.20 to 0.47)		−1.47
(−3.78 to 0.83)		0.03
(−0.47 to 0.52)		0.27
(−0.52 to 1.06)
Deming slope
(95% CI)		0.71
(0.67 to 0.75)*		0.69
(0.63 to 0.75)*		0.95
(0.60 to 1.30)		0.75
(0.68 to 0.81)*		0.70
(0.60 to 0.80)*

  • *CIs excluding the expected intercept 0 (systematic difference between the two measurements) or the expected slope 1 (disproportionate slope) were marked.

  • AMD, age-related macular degeneration; CoR, coefficient of repeatability; iAMD, intermediate age-related macular degeneration; ICC, intraclass correlation coefficient; VILL-33, Vision Impairment in Low Luminance with 33 Items; VILL, Vision Impairment in Low Luminance.