Mobility scooter driving ability in visually impaired individuals

Figures & data

Table 1. Visual characteristics per group.

Group	Definition
1. Control group (n = 37)	Binocular visual acuity ≥0.8 No peripheral or central visual field defects
2. Low visual acuity (n = 10)	0.16 ≤ binocular visual acuity ≤0.4 Intact peripheral field (peripheral VFS^a>30/40)
3. Very low visual acuity (n = 14)	0.01 ≤ binocular visual acuity < 0.16
4. Peripheral visual field defects (n = 11)	Binocular visual acuity ≥0.5 Peripheral visual field outside central 20° (peripheral VFS ≤30/40)
5. Multiple visual impairments (n = 13)	Combination of low visual acuity and visual field defect Binocular visual acuity ≤0.5 and Nonspecified peripheral visual field defect or central visual field defect inside 20° (central VFS ≤50/60)

^a VFS: Visual field score.

Table 2. Participants’ characteristics.

	Visually impaired participants (n = 48)	Normal-sighted controls (n = 37)	Test statistic (df)	p
Sex
Female	17	14
Male	31	23
Age (mean year ± SD)	61 (±7.7)	61 (±6.0)	t (83) = 0.236	0.814
Distribution of educational level (1/2/3/4/5/6/7)^a	0/2/0/3/14/22/7	0/0/0/0/13/20/4	χ^2 (4) = 4.604	0.330
MMSE^b (mean ± SD)	28.06 (±1.72)	28.43 (±1.39)	U = 797.5	0.412
Driving experience (mean year ± SD)	25 (±14)	38 (± 10)	U = 357.5	<0.001

^a (1) Less than six years of primary education. (2) Finished six years of primary education. (3) Six years primary education and less than two years of low-level secondary education. (4) Four years of low-level secondary education. (5) Four years of average level secondary education. (6) Five years of high-level secondary education. (7) University degree.

^b Mini Mental Status Examination, a screening tool for general cognitive functioning. A score below 24 indicates cognitive impairment.

Figure 1. Mobility Scooter (above) and finger-operated throttle (below).

Table 3. Descriptive statistics and comparisons between controls and visually impaired on overall performance on the driving skill test.

	Controls	Low visual acuity	Very low visual acuity	Peripheral field defect	Multiple visual impairments
N	37	10	14	11	13
Mean (SD)	18.03 (3.13)	18.20 (3.36)	18.29 (2.64)	20.73 (5.14)	21.08 (4.94)
Median	17.0^b	17.0^b	18.0^b	20.0^b	19.0^b
Post hoc^c
Mann–Whitney		183.0	225.0	133.5	132.5
U-test		0.467	0.969	0.083	0.016
p		−0.01	−0.10	−0.25	−0.34
r

^a Mann–Whitney U-test =674.0, p = 0.056, r= −0.09, compared to controls.

^b Kruskal–Wallis: H(4) = 8.01, p = 0.091.

^c Controls versus respective group with visual impairment.

Figure 2. Percentages of participants per group who needed repetitions.

Table 4. Comparison per group how often repetition was needed or not.

Group		No repetitions	Repetitions	Total
Controls (n = 37)	Count	31	6	37
	Percentage	83.8%	16.2%
	Chi-square	5.48	5.48
	p	0.019	0.019
Low visual acuity (n = 10)	Count	6	4	10
	Percentage	60.0%	40.0%
	Chi-square	0.61	0.61
	p	0.435	0.435
Very low visual acuity (n = 14)	Count	11	3	14
	Percentage	78.6%	21.4%
	Chi-square	0.52	0.52
	P	0.472	0.472
Peripheral field defect (n = 11)	Count	7	4	11
	Percentage	63.6%	36.4%
	Chi-square	0.29	0.29
	p	0.589	0.589
Multiple visual impairments  (n = 13)	Count	5	8	13
	Percentage	38.5%	61.5%
	Chi-square	7.62	7.62
	p	0.006	0.006
Total		60	25	85

Table 5. Number of repetitions per element of the mobility scooter driving skill test.

Group	Straight ahead	Stop	Reversing	Circle	Reversing around a corner	Door opening
Controls (n = 37)	0	2	5	0	0	0
Low visual acuity (n = 10)	0	0	4	0	1	0
Very low visual acuity (n = 14)	0	2	3	0	1	0
Peripheral field defect (n = 11)	0	1	4	0	1	0
Multiple visual impairments (n = 13)	0	1	8	0	5	1
Total	0	6	24	0	8	1