Effects of low visual acuity on neuropsychological test scores: A simulation study

Figures & data

Figure 1. Test Battery in chronological order of administration. NVA = normal visual acuity; LVA = low visual acuity; DART = Dutch Adult Reading Test; MMSE = Mini Mental State Examination; TMT = Trail Making Test; VOSP = Visual Object and Space Perception Battery.

Table 1. Summary of participant characteristics, visual acuity, and scores on neuropsychological tests that all participants performed with normal or corrected to normal visual acuity.

		Group A (n = 117)	Group B (n = 121)	p value	Effect size
Age		64.4 ± 8.3 [50;79]	64.6 ± 8.6 [50;79]	0.856^b	r = 0.01
Gender	Men (number)	56	61	0.694^c	Phi = 0.03
	Women (number)	61	60
Education^a		5.4 ± 1.1 [2;7]	5.5 ± 0.9 [2;7]	0.547^b	r = 0.04
Visual acuity	LogMAR	0.03 ± 0.09 [−0.16;0.24]	0.02 ± 0.10 [−0.18;0.30]	0.493^b	r = 0.04
	Decimal notation	0.95 [0.58;1.45]	0.95 [0.50;1.51]
Simulated visual acuity	LogMAR	0.75 ± 0.11 [0.52;0.96]	0.75 ± 0.10 [0.40;0.94]	0.611^b	r = 0.03
	Decimal notation	0.18 [0.11;0.30]	0.18 [0.11;0.40]
8-word test	Immediate recall total score (0–40)	32.1 ± 4.2 [22;40]	32.9 ± 4.0 [21;40]	0.202^b	r = 0.08
	Delayed recall score (0–8)	6.0 ± 1.5 [1;8]	5.7 ± 1.8 [0;8]	0.184^b	r = 0.09
	Recognition score (0–16)	15.5 ± 0.9 [12;16]	15.5 ± 1.0 [9;16]	0.581^b	r = 0.04
Clock drawing	Score (0–14)	12.7 ± 1.4 [5;14]	12.6 ± 1.5 [3;14]	0.973^b	r = 0.00
Copy drawings	Score (0–3)	1.5 ± 1.0 [0;3]	1.7 ± 1.0 [0;3]	0.183^b	r = 0.09
Bells test	Targets (0–35)	32.7 ± 2.8 [21;35]	32.6 ± 2.5 [25;35]	0.278^b	r = 0.07
	Time (s)	108.4 ± 40.6 [44;275]	104.7 ± 34.3 [54;273]	0.709^b	r = 0.02
5 point test	Number of unique patterns (3 min)	28.6 ± 9.0 [12;55]	28.3 ± 8.6 [7;50]	0.779^d	d = 0.04
DART	Estimated IQ score	102.9 ± 8.7 [81;124]	103.4 ± 9.2 [80;124]	0.701^d	d = 0.05
Verbal fluency test	Number of animals	23.9 ± 6.8 [7;43]	24.8 ± 6.5 [10;42]	0.294^d	d = 0.14
	Number of occupations	18.8 ± 4.9 [7;31]	19.1 ± 4.8 [6;31]	0.650^d	d = 0.06

Notes: Values represent mean ± standard deviation [minimum;maximum], unless mentioned otherwise.

^a Level of education according to Verhage (Duits & Kessels, 2006).

^b Mann–Whitney U test.

^c Chi-square test.

^d Two-tailed independent samples t test.

r = effect size for Mann–Whitney U tests; Phi = effect size for Chi-square tests; d = Cohen’s d effect size for t tests; DART = Dutch Adult Reading Test.

Table 2. Summary of scores on neuropsychological tests.

		Group A (n = 117)	Group B (n = 121)	p value	Effect size
MMSE	Total score (0–30)	28.1 ± 1.6 [23;30]	28.4 ± 1.4 [23;30]	0.221^b	r = 0.08
	Visual items (0–8)	7.9 ± 0.2 [7;8]	7.9 ± 0.3 [7;8]	0.187^b	r = 0.09
Balloons Test	Total targets part A (0–20)	All scored 20	All scored 20
	Time to complete part A	47.8 ± 22.7 [18;142]	31.0 ± 18.0 [11;150]	<0.001^b	r = 0.48
	Total targets part B (0–20)	19.8 ± 0.5 [18;20]	19.8 ± 0.6 [18;20]	0.750^b	r = 0.02
Complex Figure of Rey	Copy score (0–36)	25.9 ± 4.7 [7.5;34]	29.4 ± 4.3 [12;36]	<0.001^b	r = 0.40
	Copy time	149.5 ± 65.4 [69;496]	153.5 ± 68.8 [45;500]	0.647^b	r = 0.03
	Immediate recall score (0–36)	15.1 ± 6.6 [1;32]	15.2 ± 6.6 [0;29.5]	0.905^c	d = 0.02
	Immediate recall time	103.2 ± 51.2 [24;363]	106.0 ± 42.1 [35;288]	0.195^b	r = 0.08
TMT	Time part A	35.0 ± 13.2 [14;97]	52.0 ± 24.9 [15;231]	<0.001^b	r = 0.46
	Time part B	88.7 ± 67.3 [29;600]	139.2 ± 103.6 [39;600]	<0.001^b	r = 0.39
	B|A index	2.5 ± 1.1 [1.0;9.7]	2.7 ± 1.4 [0.9;9.5]	0.612^b	r = 0.03
VOSP	Screening (0–20)	19.1 ± 1.1 [15;20]	18.7 ± 1.1 [15;20]	<0.001^b	r = 0.23
	Subtest 1 (0–20): incomplete letters	19.1 ± 1.0 [14;20]	18.5 ± 1.5 [11;20]	0.002^b	r = 0.20
	Subtest 2 (0–30): silhouettes	21.8 ± 4.3 [9;29]	20.7 ± 4.3 [8;29]	0.045^b	r = 0.13
	Subtest 3 (0–20): object decision	17.6 ± 1.6 [14;20]	15.4 ± 2.5 [10;20]	<0.001^b	r = 0.46
	Subtest 4 (0–20): progressive silhouettes^a	10.9 ± 2.8 [4;19]	11.8 ± 2.7 [4;19]	0.014^b	r = 0.16
	Subtest 5 (0–10): dot counting	9.9 ± 0.4 [8;10]	9.9 ± 0.3 [8;10]	0.042^b	r = 0.13
	Subtest 6 (0–20): position discrimination	19.7 ± 0.8 [15;20]	19.7 ± 0.6 [17;20]	0.857^b	r = 0.01
	Subtest 7 (0–10): number location	9.2 ± 1.1 [6;10]	9.1 ± 1.2 [5;10]	0.995^b	r = 0.00
	Subtest 8 (0–10): cube analysis	9.4 ± 1.1 [2;10]	9.2 ± 1.6 [0;10]	0.748^b	r = 0.02

Notes: Values represent mean ± standard deviation [minimum;maximum]. The shaded areas represent the tests performed with simulated low visual acuity (LVA).

^a For this subtest, a lower score means a better score.

^b Mann–Whitney U test.

^c Two-tailed independent samples t test.

r = effect size for Mann–Whitney U tests; d = Cohen’s d effect size for t tests; p values < 0.05 and medium effect sizes printed in bold; MMSE = Mini Mental State Examination; TMT = Trail Making Test; VOSP = Visual Object and Space Perception Battery.

Table 3. Chances of scoring below the cutoff value.

		Cutoff value^a	% participants with score below cutoff value		Relative risk of scoring below the cutoff value^b
			Normal visual acuity (NVA)	Low visual acuity (LVA)
MMSE	Total score (0–30)	<24	1.7	1.7	1.0 (p = 0.973)
Balloons Test	Total targets part B (0–20)	<17	0	0	1.0 (p = 0.987)
Complex Figure of Rey	Copy score (0–36)	≤5% cutoff value (Fastenau, Denburg, & Hufford, 1999)	9.9	23.3	2.3 (p = 0.008)
	Immediate recall score (0–36)		9.1	11.2	1.2 (p = 0.590)
TMT	Time part A	<5% cutoff value (de Vent et al., 2016)	1.7	14.1	8.2 (p = 0.004)
	Time part B		5.1	20.7	4.0 (p = 0.001)
VOSP	Screening (0–20)	<15^c	0	0	1.0 (p = 0.987)
		≤15	0.9	1.7	1.9 (p = 0.588)
	Subtest 1 (0–20)	<16	1.7	4.1	2.4 (p = 0.286)
		≤16	2.6	9.1	3.5 (p = 0.047)
	Subtest 2 (0–30)	<15	6.0	9.1	1.5 (p = 0.369)
		≤15	8.5	13.2	1.5 (p = 0.253)
	Subtest 3 (0–20)	<14	0	24.8	59.0 (p = 0.004)
		≤14	5.1	36.4	7.1 (p < 0.001)
	Subtest 4 (0–20)	>15	5.1	5.0	1.0 (p = 0.952)
		>15	8.5	13.2	1.5 (p = 0.253)
	Subtest 5 (0–10)	<8	0	0	1.0 (p = 0.987)
		≤8	0.9	0.8	1.0 (p = 0.981)
	Subtest 6 (0–20)	<18	2.6	1.7	0.6 (p = 0.627)
		≤18	6.0	5.8	1.0 (p = 0.948)
	Subtest 7 (0–10)	<7	2.6	4.1	1.6 (p = 0.507)
		≤7	7.7	10.7	1.4 (p = 0.419)
	Subtest 8 (0–10)	<6	1.7	4.1	2.4 (p = 0.286)
		≤6	2.6	5.8	2.3 (p = 0.230)

Notes: Relative risks with p < 0.1 printed in bold. Sample size NVA: n = 121 for Mini Mental State Examination, Balloons Test, and Complex Figure of Rey and n = 117 for Trail Making Test and Visual Object and Space Perception Battery; Sample size LVA: n = 117 for Mini Mental State Examination, Balloons Test, and Complex Figure of Rey and n = 121 for Trail Making Test and Visual Object and Space Perception Battery.

^a Cutoff values as presented in test manuals or papers providing norm data.

^b Relative risk is calculated by dividing the proportion of participants scoring below the cutoff value in the LVA condition by the proportion of participants scoring below the cutoff value in the NVA condition. The corresponding p value is calculated as described by Sheskin (2004, p. 542).

^c The Visual Object and Space Perception Battery manual (Warrington & James, 1991) is not clear about the use of the cutoff values. Therefore, results are presented for both < and ≤ the cutoff values.

MMSE = Mini Mental State Examination; TMT = Trail Making Test; VOSP = Visual Object and Space Perception Battery.

Figure 2. Predicted scores on the Trail Making Test part A for ages 55, 65, and 75 based on the regression model. NVA = normal visual acuity; LVA = low visual acuity; TMT-A = Trail Making Test part A.

Figure 3. Predicted scores on the Trail Making Test part B for ages 55, 65, and 75 based on the regression model. NVA = normal visual acuity; LVA = low visual acuity; TMT-B = Trail Making Test part B.

Figure 4. Predicted scores on the Visual Object and Space Perception Battery subtest 3 for ages 55, 65, and 75 based on the regression model. NVA = normal visual acuity; LVA = low visual acuity; VOSP-3 = Visual Object and Space Perception Battery subtest 3.

Table 4. Regression output for the total group (n = 238). Age, vision condition, and age × vision condition entered as independent variables.

Dependent variables	Independent variables	B	t	p value	R^2
Rey Copy Score	(Constant)	25.900	63.118	<0.001	0.163
	Age	−0.137	−2.753	0.006
	Vision condition	3.461	6.027	<0.001
	Age × vision condition	0.074	1.080	0.281
TMT-A	(Constant)	35.058	21.873	<0.001	0.370
	Age	0.754	3.880	<0.001
	Vision condition	16.775	7.462	<0.001
	Age × vision condition	0.741	2.762	0.006
TMT-B	(Constant)	88.942	12.126	<0.001	0.251
	Age	2.937	3.305	0.001
	Vision condition	49.716	4.833	<0.001
	Age × vision condition	2.635	2.147	0.033
VOSP-3	(Constant)	17.546	93.938	<0.001	0.273
	Age	−0.011	−0.479	0.632
	Vision condition	−2.182	−8.329	<0.001
	Age × vision condition	−0.080	−2.565	0.011

Notes: Age = centered age variable. Vision condition is a dummy variable: normal visual acuity condition = 0; low visual acuity condition = 1 for TMT-A; TMT-B and VOSP-3; low visual acuity condition = 0; normal visual acuity condition = 1 for Rey Copy Score. TMT-A = Trail Making Test part A; TMT-B = Trail Making Test part B; VOSP-3 = Visual Object and Space Perception Battery subtest 3.

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