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From the Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom.
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Abstract |
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METHODS. Two groups of normally sighted individuals who were inexperienced in the use of a magnifier were recruited. The older group comprised 15 subjects 60 to 85 years of age, and the younger group consisted of 12 subjects 18 to 30 years of age. Subjects' reading speeds were measured under three conditions: (1) reading 12-point print without a magnifier, (2) reading 3-point print by moving a hand-held magnifier across the page, and (3) using the same print and magnifier, but moving the text under the stationary magnifier. Manual dexterity was assessed using the Jebsen-Taylor hand-function test, upper arm motor coordination with the finger-nose test, and grip strength using the Jamar dynamometer.
RESULTS. No significant difference was found between the two age groups in the mean reading speed for unmagnified text. Reading speed with a magnifier was significantly reduced in the older group, but not in the younger group. In both groups, no significant difference was found between moving the magnifier and moving the text during magnifier reading. Grip strength did not differ between the groups. The Jebsen-Taylor and finger-nose tests, however, showed poorer manual dexterity in the older group, and these correlated with the reading speed with the magnifier.
CONCLUSIONS. Manual dexterity should be considered as a possible prognostic factor for successful use of a hand-held low-vision aid. It is not known whether the deficit can be overcome with suitable training.
LVAs have been shown to be an effective means of improving reading ability in patients with impaired vision,2 3 4 but a proportion of patients do not find them useful. There are a number of visual and nonvisual reasons why patients with low-vision may have problems reading with a magnifier. Visual factors include inadequate acuity reserve and contrast reserve,5 restricted FOV,6 and the presence of a central scotoma.7 Nonvisual factors include the patient's reading comprehension,8 and training or practice with the task.9 The roles of physical and mental abilities in magnifier use have not been studied, although den Brinker and Beek10 suggested investigation of the effects of eye–hand coordination on magnifier reading. It was therefore the purpose of this study to investigate the effects of manual dexterity on the successful use of the hand-held magnifier.
A total of 77% of those who are registered as visually impaired in England are older than 65 years.11 Cross-sectional studies have shown that there is an age-related decline in dexterity.12 13 14 Motor coordination which is essential in producing smooth, controlled, and accurate movements, also shows a linear decline with age.15 This decline may be due to vascular, musculoskeletal, and/or neural problems that are common in the elderly population,16 such as minor strokes and transient ischemic attacks, joint disorders such as osteoarthritis,17 18 decrease in muscle and bone mass,19 and mild involuntary senile tremor.20
Despite the range of manual dexterity tests available, there is no single standardized test and one or more tests may be used depending on the purpose of the evaluation. Given the limited studies of the physical aspects of the use of hand-held magnifiers, the specific types of hand function needed for effective manipulation of the aid are unknown. The tests in this study were therefore selected to cover a range of abilities.
The static grip force (in pounds; often also considered to be a good indicator of general upper limb strength) can be assessed with the Jamar dynamometer21 and is obviously relevant for holding an object with adequate force to prevent slippage. Mathiowetz et al.13 reported a set of normative values for the Jamar dynamometer, finding a high correlation between grip strength and age, with the highest grip strength score reported in the 25- to 39-year age group. The Jebsen-Taylor hand-function test was designed to be an objective, comprehensive evaluation of global hand function.22 It is a timed test and addresses a broad range of different hand functions using seven subtests comprising writing, simulated page-turning, picking up small common objects, simulated feeding, stacking checkers, picking up large light objects, and picking up large heavy objects. Each of the subtests is performed according to a standardized protocol, with first the nondominant and then the dominant hand. The time needed to complete each task is recorded to the nearest 0.1 second, and the results are summed to give a global score, with lower scores suggesting better dexterity. Upper limb motor coordination is traditionally measured with the finger-nose test.23 Normative data for the test are age-dependent and show a linear decline with advancing age.15 The primary objective of the present study was to determine the relationship between manual dexterity (assessed with these three different measures) and reading rate with a hand-held magnifier, in subjects of different ages. When determining the optimum magnification or LVA for an individual patient, reading speed with the aid is an important selection criterion, in that it has the advantage of being easily quantified. Whittaker and Lovie-Kitchin5 have established that the types of reading task that the patient is likely to be able to perform will be determined by the reading speed achieved. A secondary purpose was to investigate whether there was a difference in the reading performance of naïve subjects, whether moving the magnifier or moving the text.
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Methods |
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Subjects were selected to have corrected visual acuity (Snellen) of at least 6/9, and log contrast sensitivity (Pelli-Robson) of at least 1.50 in the older subjects and 1.65 in the younger group.24 Normally sighted subjects were tested, because visually impaired subjects differ in the precise characteristics of their particular ocular disease and the consequent effect on reading; they are prescribed different types and powers of magnifier and have variable levels of experience and training in their use; and the hand-function tests, most of which are visually demanding, were not designed or adapted for the visually impaired.
To provide a representative sample of the type of individuals referred to low-vision clinics, subjects with arthritis, impaired upper limb function or history of vascular conditions such as transient ischemic attacks or strokes were not excluded from the study. Cognitive function was measured with the Mini Mental State Examination (MMSE; adapted from Folstein et al.25 ). All subjects had normal scores (maximum, 30), and there was no significant difference between the two age groups (29.20 ± 0.94 vs. 29.75 ± 0.45; P = 0.075).
No assessment of the individual subjects' reading ability or comprehension was carried out. All had English as their preferred language.
Reading Performance
Reading speed was recorded under three conditions: (1) reading 12-point print without magnification (UNMAG), (2) reading 3-point print by moving the magnifier across the page (MOVEMAG), and (3) reading 3-point print by moving the text under the stationary magnifier (MOVETEXT).
The text samples used were three short passages (approximately 600 words each) that had been used in research on reading comprehension.26 27 Each passage was a meaningful story, and subjects were instructed to correct themselves if they realized that they had missed lines or words. The readability grades of the three passages were 8.8, 7.3, and 6.6 (Flesch-Kincaid scale), respectively. The texts were randomized to the different conditions, and no subject read a passage more than once. Each was printed fully justified over 15 lines, each containing 12 to 13 words: obviously the small print lines covered a shorter linear distance (31 mm). The power of the hand-held magnifier used was rated by the manufacturer as 5x (model 265560; Eschenbach Optik, Nürnberg, Germany). It consisted of a 58-mm diameter aspheric bi-convex lens with front surface power, +11.66; back surface power, +8.33; center thickness, 17.4 mm, refractive index = 1.498; and equivalent power, +19.00 DS.
To create an equivalent magnification in the two subject groups, the older group were asked to use their reading correction (the manufacturer recommends an eye-to-image distance of 40 cm28 ). It was assumed that despite instructions to maximize the magnifier-to-page distance, the young subject group would exert some (proximal) accommodation. It is therefore estimated that all subjects experienced an equivalent power for the two-component system (magnifier and typical add/accommodation of +2.50) of approximately +12 to +14.4 DS (depending on the eye-to-magnifier distance, which was between 14 cm as recommended by the manufacturer and 20 cm, the maximum actually used by any subject). The magnification relative to the unmagnified print at the average habitual reading distance of 30 cm was therefore 3.6x to 4.3x. The viewing conditions were not rigidly fixed during the experiment, but the required acuity reserve to achieve the critical print size (up to 3:15 ) is easily met for subjects with a minimum acuity of 6/9, and the calculated magnification causes 3-point print to have the same retinal image size as unmagnified 10.8- to 12.9-point print. The FOV with this magnifier was more than 60 characters long at the recommended magnifier-to-eye distance. This FOV is well beyond the total perceptual span of approximately 20 characters identified as necessary for everyday reading of normal text, involving a staircase pattern of saccadic eye movements.29
The same protocol was used for each reading condition. The subjects were informed that the reading was to be timed, but that they should read accurately at their normal speed rather than trying to complete the task in the shortest time possible. No verbal prompts, encouragements, or interruptions occurred during the test. Reading speed was calculated as the number of words read correctly per minute. Words missed or misread were excluded from the calculation: words read twice were counted only once.
Subjects first read the 12-point print aloud, with their reading correction if worn (UNMAG).
The same text used in the unmagnified reading, but produced in 3-point print, was used to train the subject to use the magnifier. Subjects then read with the magnifier under two different conditions—MOVEMAG and MOVETEXT—the order of which was randomized. The text was placed onto a clipboard and subjects held the magnifier in one hand and the clipboard in the other.
For training, subjects read the text sample once, with prompts and encouragement from the experimenter, according to a prearranged protocol.
Because of the compact size of the magnifier compared with the cumbersome clipboard with the text, normal subjects were expected to find the "moving text" condition difficult. To avoid this problem, the practice session was conducted twice, first with the text in the nondominant hand and then in the dominant hand. At the end of the second practice session, subjects were given a choice as to which hand they used to move the text with during the following timed reading session. Subjects showed a unanimous preference for moving the text with the dominant hand. The session under timed conditions took place immediately after the practice session.
Manual Dexterity Measurements
Manual dexterity was measured with three different tests, in the following order.
Jebsen-Taylor Hand Function Test.
This is a seven-part test that is used to assess global hand dexterity, and testing was performed according to the standard protocol. All parts of this test were timed and subjects had to complete each task in the shortest time possible. The seven subtests were administered in the standard order22 : handwriting, simulated page turning, picking up small common objects, simulated feeding, stacking checkers, picking up large, light objects, and picking up large, heavy objects. Each test was performed only once with each hand, first the nondominant (results not reported here) followed by the dominant hand.
Grip Strength Measurement.
This was assessed with a standard Jamar hydraulic hand dynamometer. The subjects were asked to sit with the shoulders facing the examiner in front, the elbow flexed at 90°, and the forearm in neutral position with the wrist between 0° and 30° dorsiflexion. The dynamometer was firmly held in this position, and the subjects were asked to squeeze the handle as hard as they could. Grip strength measures were recorded for both the dominant and nondominant hand in random order. The results were recorded in pounds, and the final score for each hand was taken as the average of three attempts. A rest period of 30 seconds was given between each attempt.
The Finger-Nose Test.
This test was used to measure the upper limb motor coordination of subjects in a series of fast, accurate, repeated movements of the arm. After a short demonstration and practice, the subjects were asked to place the index finger of the dominant hand on the nose and then extend the arm to touch a target that was placed level with the nose at the distance of the fully extended arm. After touching the target, they had to touch the nose again. This series of movements was counted as one complete cycle and the subjects were timed while performing three cycles as quickly and accurately as possible. The final result analyzed was the mean of three repetitions of the full test (i.e., the mean time taken to perform three cycles of the movements). Characteristics of the movements such as dysmetria (imprecision in making a movement) or tremor were not recorded.
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Results |
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Reading speeds with the magnifier were converted to relative scores for both moving the magnifier (RELMAG) and moving the text (RELTEXT). The result was determined by dividing the speed of reading with the magnifier, by the subject's unmagnified reading speed. Little difference was found between magnified reading moving the magnifier or the text (i.e., RELMAG showed no significant difference from RELTEXT). This result was true of both the older and younger groups.
Table 2 shows the mean and standard deviation of the manual dexterity scores for both groups of subjects. One-way analysis of variance (ANOVA) was used to compare the older and the younger groups for each of the dexterity tests. The dexterity scores were those obtained with the dominant hand only, because this was the hand used in each reading condition to manipulate the moving object. There were significant differences between the two groups in the Jebsen-Taylor total scores (i.e., the time for all the seven subtests added together) and the results of the finger-nose test. Measurement of grip strength, however, showed no significant difference between the groups. All but two of the Jebsen-Taylor subtests showed significant differences between the older and the younger groups of subjects. Picking up large heavy objects showed the most significant difference. The handwriting subtest contributed heavily to the total score, because it is the task that takes the longest to complete, and it also showed a significant difference between the two age groups. The only two subtests that showed no significant difference between the groups were simulated page turning and simulated feeding.
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Discussion |
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Reading speed without a magnifier was not significantly different between the older and the younger groups of subjects. This finding indicates that age alone is not a significant independent predictor of performance, in accordance with the results of Lott et al.33 Reading speeds for the younger group were similar regardless of the reading conditions. Differences between their average reading speeds, with and without a magnifier were not significant. Reading rate with a magnifier, however, was found to be reduced significantly in the older group. This result was apparent when compared either to the performance of the younger group or (within group) to the older group's baseline (unmagnified) reading speed.
By the time patients are referred to a low-vision clinic for assessment, they will often have tried some sort of commercially available magnification aid. When naïve users are reading with a magnifier, the natural tendency is to move the magnifier along the page, particularly since they also tend to use a long eye-to-magnifier distance. In low-vision clinics, however, patients may be taught to use a steady-eye strategy, whereby the magnifier is held steady at a fixed distance from the page and patients read by moving the page under the magnifier. Clinical experience suggests that it is often difficult to retrain patients who are accustomed to moving the magnifier to move the text instead. Moving the text is particularly beneficial, however, when the FOV is small, either because of magnifier limitations, or because of the patient's eye condition. In this study, the two groups of naïve subjects were trained to use both of these methods for reading with the magnifier, and reading speed was (unexpectedly) the same in both conditions, presumably because, in this study, the subjects were actively encouraged to try moving the page with either hand, and all then chose to read by moving the text with the dominant hand. It is well-known that the nondominant hand has poorer dexterity,22 and so this seems a sensible strategy. (All the subjects in this study performed worse in the dexterity tests with their nondominant hand, but as none of them chose to use that hand for either task, we have not reported these data). However, low-vision patients who have been accustomed to holding the magnifier with the dominant hand are unlikely to swap hands spontaneously when asked to move the text instead. Protocols for LVA training vary between clinics and practitioners, and we do not know whether, in general clinical situations, low-vision patients are encouraged to switch hands when adopting the page-moving strategy. Although we do not know whether this would be equally beneficial to the experienced user, we recommend that this strategy be considered.
Dexterity scores, as determined by the increased time taken for the Jebsen-Taylor and the finger-nose tests, showed a significant reduction in hand function in the older group of subjects in agreement with the findings of Jebsen et al.22 and Desrosiers et al.15 Grip strength, however, showed no significant difference between the two age groups, in contrast to the results of Mathiowetz et al.13 This may be the result of a gender bias, since men tend to have greater grip strength than do women.13 34 In the present study, there was (by chance) a gender bias toward the women in the younger group of subjects with the ratio of 3:1; whereas the older group had more male participants. Josty et al.35 have also reported that those who perform heavy manual work had the strongest grip, whereas office workers had the weakest. All the younger subjects were students, and the older group was retired, but their past occupations may have influenced grip strength. When the analysis was controlled for gender (partial correlation coefficient), a significant correlation was found in the present study between grip strength and relative reading speed (r = 0.42, for relative speed when moving the magnifier; P = 0.029).
Despite the significant differences found between the two groups in the total Jebsen-Taylor score (older group: 52.26 ± 11.77; younger group: 37.29 ± 6.86), some subtests revealed smaller or negligible differences between the groups. Simulated page turning and simulated feeding were found to show very little difference between the two groups. The latter finding was also reported by Jebsen et al.,22 and Hackel et al.12 found differential effects of age on the different subtests. It is possible that the particular hand functions involved are not as susceptible to aging, or that those tasks (particularly feeding) with which individuals are involved on a daily basis may not be so susceptible to decline. If this is the case, it suggests that the regular use of a magnifier may help to preserve the dexterity skills needed to continue to use it. Therefore, one might suspect that experienced magnifier users who are good at manipulating the aid may also show unusually good performance on certain dexterity tests because of the continual reinforcing of those skills while using the aid.
It is not known whether prolonged practice can actually improve dexterity generally or the use of the magnifier in particular. The effect of short-term practice on results of the Jebsen-Taylor test has been found to be insignificant, since the test has excellent test–retest repeatability.22 It is possible, however, that longer-term training would be effective, so long as the patient did not become too discouraged by an early lack of success.
Manual Dexterity and Reading Performance
Analysis of the results from all 27 subjects showed a significant correlation between the manual dexterity and reading speed with the magnifier. The strongest correlation was found with the finger-nose test, independent of whether subjects moved the magnifier or the text. To be sure that the result we found was due to the effect of manual dexterity, it was important to eliminate any other possible factors that could affect reading speed with a magnifier. Even though the subjects in both groups had normal corrected visual acuity and contrast sensitivity, these abilities are age dependent, and so the mean performance of the younger group would inevitably be significantly better. We suggest, however, that this was not a significant factor in this experiment, because the subjects acted as their own controls, with performance being compared with and without the magnifier. Any effects of reduced acuity or contrast sensitivity on reading performance would therefore be present in both conditions. The FOV of the magnifier was identical for both groups, and the acuity reserves, contrast reserves, and the FOV of the magnifier for both groups were above the level recommended by Whittaker and Lovie-Kitchin5 for high-fluency reading. None of the subjects had any cognitive impairment, as measured with the MMSE, which may have affected their ability to understand the training they received.
The most obvious potential confounding factor is age. It is possible that age has a concurrent effect on both manual dexterity and reading performance. If this were true, correlations between dexterity and reading performance could exist simply because they were both affected by age, but in fact there may be no direct relationship between the two. However, it was found that the correlation remained significant when performed within group, thus correcting for the influence of age.
There were interesting differences in the correlations found between the individual subtests in the Jebsen-Taylor and the reading speed. Because it is difficult to determine the specific types of hand function needed to manipulate a hand-held magnifier, we cannot speculate on reasons for the relationships found. This finding does affirm, however, the claim by Jebsen et al.22 that the design of the dexterity test measures different aspects of hand function. It also suggests that several different aspects of hand function are involved in magnifier use. The subtests which showed the strongest correlation to reading with a magnifier were handwriting and picking up large, heavy objects: on the contrary, simulated page turning and simulated feeding showed no correlation. Although we tested a wide range of dexterity skills, there may be other equally relevant aspects of hand function that we did not consider.
Although the Jebsen-Taylor test is standardized and has been shown to be valid and repeatable, it is time-consuming and exacting to set up. It is also heavily reliant on good vision (e.g., the handwriting test), and could not therefore be used directly for visually impaired subjects. The finger-nose test result showed the best correlation to reading speed. It is quick to perform, does not rely so heavily on good vision, requires little training of the subject, and in this study showed a high correlation with the total Jebsen-Taylor score (r = +0.674 for the dominant hand). Unfortunately, the method of performing the test varies, accurate timing may be difficult, and repeatability has not been determined. Further studies of this test are needed to determine its practicality and clinical prognostic usefulness.
The results of this study suggest that manual dexterity could be a significant factor in determining the reading rates of untrained individuals when using a hand-held magnifier. It is acknowledged that in the case of patients with low-vision, this would be most likely to apply to those who otherwise had no visual contraindications to fast reading: that is, they had appropriate acuity reserve, contrast reserve, and scotoma size.5 For subjects whose visual characteristics limited the potential for fast reading, a dexterity limitation may be less significant. The results of this study, however, suggest that dexterity testing could be useful in identifying elderly patients who may have difficulties reading with a magnifier because of their physical abilities. This could assist clinicians in making a decision concerning the best type of magnifier to prescribe, to help minimize rejection by patients and avoid delay in visual rehabilitation. This study suggests that further research on the effect of dexterity on magnifier reading is warranted, but it appears sensible to counsel those individuals with poorer dexterity to choose a magnifier that requires less handling (for example, a bar or a stand magnifier) and to hold any objects that need to be manipulated with the dominant hand.
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Footnotes |
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Disclosure: C. Dickinson, None; M. Shim, None
The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked "advertisement" in accordance with 18 U.S.C. 
1734 solely to indicate this fact.
Corresponding author: Chris Dickinson, Faculty of Life Sciences, University of Manchester, Moffat Building, PO Box 88, Manchester, M60 1QD, UK; chris.dickinson{at}manchester.ac.uk.
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