Prismatic displacement effect of progressive multifocal glasses on reaction time and accuracy in elderly people

Figures & data

Figure 1 A flight of stairs viewed through a left, plano + 4D power progressive lens.

Note: Dotted lines represent the section of lens that was mapped.

Figure 2 Vertical prismatic displacement measured by the focimeter.

Notes: The different shades correspond to the degree (mm) and direction of displacement (see legend). Red indicates maximal displacement and blue indicates no displacement. Negative (−ve) indicates negative number or downward displacement and positive (+ve) indicates positive number or upward displacement.
Abbreviation: PAL, progressive addition lens.

Figure 3 Horizontal prismatic displacement measured by the focimeter.

Notes: The different shades correspond to the degree (mm) and direction of displacement (see legend). Red indicates maximal displacement and blue indicates no displacement. Negative (−ve) indicates negative number or leftward displacement and positive (+ve) indicates positive number or rightward displacement.
Abbreviation: PAL, progressive addition lens.

Figure 4 A diagram that represents the equipment used to measure accuracy.

Notes: Center of the diagram is the veroboard containing nine switches and above it is a line (1 mm thick and 68 mm long tape) on a foam pad (5 mm thick) which was placed on top of the veroboard. Height and length of the veroboard were 75 mm and 130 mm, respectively. Switches were raised 1 mm from the veroboard by foam and each was spaced 7 mm apart in the vertical axis. On the left is the different voltage (v) input to each switch; on the right is the channel input into the PowerLab^® 4SP data acquisition system (ADInstruments, Dunedin, New Zealand).

Figure 5 LabChart^® display window.

Notes: Displayed are outputs (voltage spike, a single line) from and inputs (sustained voltage, column shape) to the PowerLab^® 4SP data acquisition system (ADInstruments, Dunedin, New Zealand) over time. Note that the input in channel 1 (red line) is 9 v and the input in channel 4 (pink line) is 3 v. Three different voltage inputs were used with four channels to the PowerLab^® data acquisition system, which effectively became a potential 12 switches (only nine were needed). Output from the PowerLab^® data acquisition system turned on the light stimulus. On the left is the video capture of the participant’s action. LabChart Pro^® version 7 (ADInstruments, Dunedin, New Zealand).
Abbreviation: v, voltage.

Figure 6 Diagram illustrating the Mobilis^® Quad walking frame in the center and the three major components attached to the frame.

Notes: Top left is a picture of the line on a foam pad, top right is the bar to grasp, and bottom right is the brake pad and switch activated by the grasp bar. The bar measured 100 mm in length and 40 mm in thickness; the black line measured 68 mm in length and 1 mm in thickness. Mobilis^® Quad (Cubro Ltd, Tauranga, New Zealand).

Figure 7 Participant recruitment.

Abbreviations: MMSE, Mini Mental State Examination; n, number; PALs, progressive addition lenses; VA, visual acuity.

Table 1 Characteristics of participants (n=31), where values are numbers (percentages) unless otherwise stated

Demographic factors
Mean (± SD) age (years)	79 (3.4)
Men	12 (38.7)
New Zealand European	29 (93.5)
Living arrangements
Own home	28 (90.3)
Living alone	13 (41.9)
>1 hour home help, per week	3 (9.7)
Meals on wheels	2 (6.5)
Medical conditions
Mean (± SD) MMSE# score^Citation13	27.7 (1.1)
One or more falls in previous year	12 (38.7)
Number of participants who had a fall wearing PALs	6 (19.4)
≥average subjective health‡	27 (87.1)
Stroke	4 (12.9)
Parkinson’s disease	1 (3.2)
Hip fracture	1 (3.2)
Hip/knee pain	6 (19.4)
Diabetes	4 (12.9)
Other medical problems	10 (32.3)
Medication use
Four or more medications	20 (35.5)
Psychotropic medications	3 (9.7)
Vision and physical function
Mean (± SD) length of time wearing PALs (days)	228 (SD 146)
Mean (± SD) visual acuity (logMAR##)	1.38* (0.38)
Mean (range) power of reading portion of PALs	2.53 (2 to 3)
Mean (± SD) edge contrast sensitivity (dB)	15 (2.4)
Mean (± SD) sit to stand five times test (s)	17 (7.7)
Mean (± SD) FICSIT 4 score^Citation15	4.0 (1.1)
Mean (± SD) FES-I fall anxiety score**,^Citation16	23.0 (5.4)
Mean (± SD) AAP score‡‡,^Citation17	61.4 (8.7)
Mean (± SD) length of time with PALs (years)	11.8 (10.7)

Notes:

# Mini Mental State Examination;

‡ subjective health is a scale including excellent, very good, good, fair, and poor; above average subjective health is good and better;

## minimum angle resolvable in minutes of arc;

* approximate Snellen equivalent 6/9 to 6/6;

** not anxious about falls (16 not anxious, 64 very anxious);

‡‡ middle for activity level (21 unfit, 84 ft).

Abbreviations: MMSE, Mini Mental State Examination; SD, standard deviation; PALs, progressive addition lenses; FICSIT 4, Falls and Injuries: Cooperative Studies of Intervention Techniques balance scale; FES-I, Falls Efficacy Scale International; AAP, Adelaide activities profile.

Figure 8 Reaction time measurements for grasping a bar at the various points of fixation while wearing the two glasses.

Notes: The black line on the glasses illustrates a significant difference of reaction time and orientation of the equipment. Black represents PALs and white represents single vision (distance) glasses. *P-value associated with repeated measures analysis ≤0.05.
Abbreviation: PALs, progressive addition lenses; R, right; s, second.

Figure 9 Reaction time measurements for pushing a black line at the various points of fixation while wearing the two glasses.

Notes: The black line on the glasses illustrates a significant difference of reaction time and orientation of the equipment. Black represents PALs and white represents single vision (distance) glasses. *P-value associated with repeated measures analysis ≤0.05.
Abbreviations: PALs, progressive addition lenses; T, temporal; N, nasal.

Table 2 Reaction times (seconds) for reaching the targets and the difference in displacement between the two glasses (millimeters) at each position tested

Deviation from center (degrees)	Position of bar or line seen through the glasses	Displacement of participants’ PALs compared to matched single vision glasses (mm)#		PALs (s)		Single vision distance glasses (s)		Comparison with repeated measures for order effect, updated PALs and prismatic displacement (s)
		Mean difference (95% CI)	P-value	No	Mean (SD)	No	Mean (SD)	Difference (95% CI)	P-value
0	Center of lens
	Horizontal
	Bar	8.15 (6.54–9.75)	<0.001##	31	1.105(0.332)	31	1.206(0.340)	−0.101 (−0.203, <0.001)	0.011##
	Line			31	1.181 (0.478)	31	1.154(0.358)	0.027 (−0.054, 0.107)	0.963
	Vertical
	Bar	0.56 (−0.46–1.59)	0.271	30	1.223(0.326)	30	1.232(0.266)	−0.009 (−0.063, 0.044)	0.224
	Line			31	1.063(0.321)	31	1.089(0.281)	−0.026 (−0.070, 0.018)	0.413
	300 mm below center of lens
	Horizontal
	Line	0.97 (−0.75–2.68)	0.258	31	1.032(0.279)	31	1.112(0.049)	−0.080 (−0.113, −0.046)	0.007##
35	100 mm below center of lens
	Horizontal
	Bar	1.83 (0.52–3.14)	0.008##	30	1.080 (0.269)	30	1.117(0.278)	−0.037 (−0.110, 0.036)	0.444
	200 mm below center of lens
	Vertical
	Bar	2.23 (0.37–4.09)	0.020	31	1.152(0.280)	31	1.145(0.319)	0.007 (−0.059, 0.100)	0.558
	Line			30	0.959 (0.239)	30	0.953 (0.221)	0.006 (−0.043, 0.054)	0.714

Notes:

# Horizontal and vertical displacement is opposite to the position of the bar, and measurements were made with the focimeter;

## significant if P<0.05.

Abbreviations: No, number; SD, standard deviation; CI, confidence interval; PALs, progressive addition lenses.

Figure 10 The pie graphs represent accuracy of the participant when pushing the black line on a foam pad at the various points of fixation.

Note: Black indicates the subject pushed the black line and white indicates they missed it.
Abbreviations: PALs, progressive addition lenses; T, temporal; N, nasal.

Table 3 Accuracy measurements in binomial distribution for each of the positions tested

	Single vision (distance) glasses		Total
	Accurate	Not accurate
Horizontal at center*
PALs
Accurate	7 (23%)	5 (16%)	12 (39%)
Not accurate	6 (19%)	13 (42%)	19 (61%)
Total	13 (42%)	18 (58%)	31 (100%)
Vertical at center**
PALs
Accurate	3 (10%)	10 (32%)	13 (42%)
Not accurate	3 (10%)	15 (48%)	18 (58%)
Total	6 (19%)	25 (81%)	31 (100%)
Horizontal at 300mm below center#
PALs
Accurate	6 (19%)	3 (10%)	9 (29%)
Not accurate	8 (26%)	14 (45%)	22 (71%)
Total	14 (45%)	17 (55%)	31 (100%)
Vertical at 35° peripherally 200mm below center##
PALs
Accurate	7 (23%)	2 (7%)	9 (30%)
Not accurate	6 (20%)	15 (50%)	21 (70%)
Total	13 (43%)	17 (57%)	30 (100%)

Note: McNemar Test

* P=1.000,

** P=0.092,

# P=0.227,

## P=0.289.

Abbreviation: PALs, progressive addition lenses.

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