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Satisfaction Level of Progressive Additional Lens (PALs) Wearers


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The number of presbyopia is increasing worldwide with highly reported on an inadequate correction, which can reduce the visual satisfaction. A survey was conducted to study the level of vision satisfaction between the quality of vision and symptoms reported by progressive addition lens (PALs). Sixty questionnaires were mailed to the (PALs) wearers aged between 40 years and above from Universiti Teknologi Mara (UiTM) Vision Care. The strongest correlation was found between the quality of vision at intermediate viewing with total satisfaction on seeing grocery shelves and computer screen with p<0.001. PALs wearers priority and needs should be considered in selecting the appropriate lens design to be matched for required tasks.
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ASLI QoL 2017
3rd ABRA International Conference on Quality of Life
“Quality of Life 3”
Riverside Majestic Hotel, Kuching, Malaysia, 14-16 Oct 2017
eISSN: 2398-4287© 2017. The Authors. Published for AMER ABRA by e-International Publishing House, Ltd., UK. This is an open access article under the CC BYNC-
ND license ( Peerreview under responsibility of AMER (Association of Malaysian Environment-Behaviour
Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning &
Surveying, Universiti Teknologi MARA, Malaysia.
Satisfaction Level of Progressive Additional Lens (PALs) Wearers
Nur Aresya Ahmad Najmee, Noor Halilah Buari, Rabiatun Mujari, Muhammad Irwan Rahman
Optometry, Faculty of Health Sciences,
Universiti Teknologi MARA, 42300 Bandar Puncak Alam, Selangor, Malaysia
The number of presbyopia is increasing worldwide with highly reported on an inadequate correction, which can reduce the visual satisfaction. A
survey was conducted to study the level of vision satisfaction between the quality of vision and symptoms reported by progressive addition lens
(PALs). Sixty questionnaires were mailed to the (PALs) wearers aged between 40 years and above from Universiti Teknologi Mara (UiTM) Vision
Care. The strongest correlation was found between the quality of vision at intermediate viewing with total satisfaction on seeing grocery shelves and
computer screen with p<0.001. PALs wearers priority and needs should be considered in selecting the appropriate lens design to be matched for
required tasks.
Keywords: Level of satisfaction; quality of vision; multifocal lens; progressive additional lens.
eISSN: 2398-4287© 2017. The Authors. Published for AMER ABRA by e-International Publishing House, Ltd., UK. This is an open access article under the CC BYNC-
ND license ( Peerreview under responsibility of AMER (Association of Malaysian Environment-Behaviour
Researchers), ABRA (Association of Behavioural Researchers on Asians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning &
Surveying, Universiti Teknologi MARA, Malaysia.
1.0 Introduction
Presbyopia affects the quality of life (Patel & West, 2007). Presbyopia is the most common physiological change that occurs in the
most adult eye and expected to impact billions of people worldwide (Chu, 2010). According to Laviers et al., (2009), presbyop ia is
projected to impact 1.04 billion of people in which 517 million people were left inadequately fixed. Furthermore, (McDonnell et al.,
2003) suggested that the association of presbyopia have an adverse impact towards the life of United States population. The normal
young eyes can easily focus on near or distant objects (Werner et al., 2000). This ability diminished towards old age.
According to Helmholtz’s theory, the cause of presbyopia is due to the loss of elasticity of the crystalline lens in which the changes
or contraction in the ciliary muscle and choroid become less efficient with age. The loss of elasticity will cause the lens to resist in
changing its shape and focus on near and distant objects (Chu, 2010). Due to ageing, the capability of reading small prints at a normal
distance decreases as blur increases. Progressive degeneration combined with inadequate illumination, as light affects the human
vision (Wahab & Zuhardi, 2013), normal size print will soon diminish. The onset of presbyopia is considered to occur when the
amplitude of accommodation has decreased to 5.00D or less (Grosvenor, 2007). As the amplitude of the accommodation diminished,
the range of clear vision at near will reduce due to the disturbance and difficulties in more frequent or demanding near vision tasks.
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A self-administered questionnaire by the National Eye Institute of Refractive Error Quality of Life was conducted and found out that
inadequate optical correction of people with presbyopia has been found to give adverse effects on their health-related quality of life
(Chu, 2010). The daily life of people suffering from visual impairment can be affected (Malinovska & Majerova, 2015). An effective
optical correction by using spectacles is one of the solutions to remediate presbyopia. It remains as the most shared and cost-effective
presentation worldwide (Marmamula et al., 2013). By prescribing reading additions based on patient’s age would be the most
successful method to determine correction addition required for the presbyopic patient (Leary & Evans, 2003).
There are several choices of prescription or procedure to correct presbyopia. For example, a single vision lens for near correction.
Another type of lenses such as bifocal or trifocal lenses, progressive or multifocal lenses, progressive contact lens or surgery can also
be used to accommodate presbyopic patients. Initially, the majority of presbyopes were prescribed to use progressive addition lenses
(PALs), which followed by bifocal or trifocal spectacles (Chu, 2010). Nevertheless, the use of progressive addition lens (PAL) is the
ideal spectacle correction for presbyopia due to the property less distortion, which can provide a continuous progression in power for
clear vision at all distances (Lynn, 1998). The property of progressive lens on PALs, enables a continuous clear vision at a distance,
intermediate and near in which the dioptric power will gradually increase along the lens surface from the upper to the lower portion
(Odjimogho, 2004). Gradual changes in plus power for about 0.12D steps can barely eliminate the jumping image due to the rotation of
distance to near portion, which caused by the seamless transition of power. Furthermore, the design of PALs in regard of the curves,
known as curvature, is taken into consideration, as to allow the customisation on the wearer habits and characteristics such as
occupation, age, head movements and relative velocity (Savio, Concheri, & Meneghello, 2011).
Figure 1.1 Arrangement of a PAL lens.
The majority of PALs wearers have the acceptance rate at 90% or more due to the comfortability and the quality of vision that PALs
provided (Hons, 2008). It has become one of the most competent presbyopic management and an excellent choice for presbyopia
wearer as compared to bifocal lenses. The high acceptance rate of PALs can be due to the elimination of imaginary lines and jumping
images in which reduce the sudden change in the prismatic and increase the comfortability of the wearers (Walsh, 2001). Odjimogho
(2004) surveyed 106 PALs wearers aged between 37 to 66 years old. 69.8% of patients have a high rate of comfortability with their
PALs. Younger patients have achieved more comfortable fit as compared to older patients. This may occur due to the easier
adaptation of the early presbyope as compared to the late presbyope. A previous study by Han et al., 2011, has compared patients
satisfaction with progressive lenses with other types of presbyopic correction. They revealed pout that most the subjects involved has
were satisfied with progressive lenses rather than other type of lenses (Han et al., 2011). Overall, the multi-design lens scored the
highest in the areas of quality of vision, ease of adaptation and patient satisfaction (Lynn, 1998). Moreover, cosmetically, PALs offer a
desirable additional power without the lines and ledges that fundamentally „blend the transition between distance and near zones
(Meister & Fisher, 2008).The blending is by a various amount of astigmatism that oriented at the oblique axis. The ability to alter the
dimension from the distance to intermediate and near were also influence the high comfortability with PALs wearers. It represented the
overlapping of multiple individual focal points, where each have their own range of clear vision, hence providing a single, broad
expanse of clear vision from infinity to near distance (Gispets, Pujol, & Vilaseca, 2011). Clear vision is possible to some e xtent at all
distances and certainly increased the quality of vision (Walsh, 2001). According to Gime, 2008, although bifocal lenses were more
appreciated for their near field of view, progressive lenses have had a very high success (97%) since the 1970s (Gime, 2008). A
previous study by Spaulding (1981), involving 48 multifocal candidates and their preferences of multifocal lens design. 52% preferred
PALs lenses as compared to bifocal design (48%) (Lynn, 1998). According to (Chu, 2010), one study demonstrated that up to 92% of
previous bifocal wearers preferred progressive addition lenses (PALs) when given a choice between PALs and bifocal lenses following
a trial of PALs. The line on bifocals is not particularly attractive for younger presbyopes. Ninety-two percent of patients involved in the
study by Boroyan et al. (1995) preferred PALs as compared to a lined multifocal due to the cosmetic purposes (Lynn, 1998). The
success of the visual performances with PAL spectacles was correlated with the optics of the lenses, the fit of the frame and the
position wear including eyes and head movement for visual tasks at a different viewing distance and the individual characteristics of
the patient. Hence, the adaptation and satisfaction PALs have been hampered by several problems. The primary disadvantage of PAL
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is the restricted optical zones. This makes reading at both intermediate and near distances a problem (Spencer & Ciuffreda, 2002).
Restriction of this optical zone will lead to the increment frequency of the compensatory head movement to get clear vision.
Furthermore, the prismatic effect of the lateral sides of PALs. This will cause the presence of unwanted peripheral astigmatism, which
is induced by the continuous change in power through the lens. PALs wearers may be aware of the lateral image blur that can
adversely affect the success of the adaptation process (Mok, Chung, & Kwok, 2011). Thus, most of the PALs wearers
complained of vertigo and dizziness when changing gaze horizontally (Suemaru, Hasebe, & Ohtsuki, 2008).
PALs wearers were also needed to view the appropriate part of the lens to obtained clear vision depending on the
distance of the object. Moreover, the progressive lens costs more than other types of correction lenses for presbyopia. Consequently,
due to all of these problems, some patients are not satisfied enough with their spectacle correction. Therefore, a survey of patients
satisfaction on wearing progressive additional lenses was conducted. In this study, we systematically review patients’ feedback on
progressive additional lenses provided by UiTM Vision Care regarding the quality of vision and associated symptoms occurred. It is
fundamental to evaluate the satisfaction level of vision among presbyopic patients with PALS as well as to enhance the services
provided by UiTM Vision Care.
2.0 Methodology
2.1 Research Design
A cross sectional survey design was chosen to answer the research aims and objectives. Data was collected at a particular time
in one session for a defined population.
2.2 Research Settings and Participants
Sixty respondents aged between 40 years old and above were selected from UiTM Vision Care (optometric clinic and practice in
Universiti Teknologi MARA). Those who were wearing progressive addition lens for other reasons such as myopia or
accommodation were excluded from this research. Respondents were selected from patients records and enlisted using
convenience and availability sampling method. Patients records were obtained by accessing their archived receipt for the
purchase of progressive additional lenses (PALs) that was prescribed from UiTM Vision Care. The selection was based on the
patients prescription from February 2014 through February 2015.
2.3 Instrument
A questionnaire was adopted from The Ohio State (DAI-B 59/08, p. 4217, Feb 1999) to evaluate the satisfaction level of visual
performance based on respondents’ daily activities. The questionnaires were divided into three parts; namely (1) demographic
details, (2) respondents feedback, and (3) symptoms reported by the PALs wearers. The questionnaire was given via email,
post and by other types of communication services. Demographics questions were developed to collect the respondents’
information. The questions regarding visual performances at distance viewing, intermediate viewing and near vision with the
total satisfaction of progressive additional lens (PALs) prescribed were calculated using a Likert scale. Symptoms occurred while
wearing the PALs was also recorded in the questionnaires. The Likert scale has been used as it is a simple, reproducible, quick
and reliable in measuring the patients satisfaction level (Hiraoka et al., 2009).The questionnaires had 10-point Likert responses
scales ranging from 0, which represented as ‘totally unacceptable’ to 10 which described as ‘excellent’ for part (2). Except for
part (3) which is related to symptoms experienced by respondents, the responses scale ranging from 0-10 which is ‘extremely
bad’ to ‘none’ respectively. The scores were converted into percentages, the higher the rate, the level of satisfaction
respondents using the PALs was assumed as increased. Total satisfaction of PALs wearer was determined by adding all
responses in part (2) which give a total score of 100.
2.4 Data Analysis
All data were analysed using SPSS software version 21.0. The descriptive data respondents were shown regarding the mean
and standard deviation. Satisfaction level was analysed using linear regression to determine the correlation between the
qualities of vision with total satisfaction. As for the relationship between quality of vision, wearing hours and associated
symptoms with total satisfaction, Spearman rank correlation was used. Findings with a p-value <0.05 were considered to be
statistically significant.
2.5 Ethics
The study was approved by Research Ethics Committee of Universiti Teknologi MARA (UiTM). The aims and objectives of the
study were explained to all respondents, and informed consent forms were obtained.
3.0 Result
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3.1 Respondents profile
The questionnaires were mailed out to the sixty respondents that were selected from UiTM Vision Care. From the sixty questionnaires,
only thirty-two questionnaires were given back, which gave the total of 53.3% of response rate. However, due to the invalid response
and the involvement of glaucoma disease by the respondents, another two questionnaires were excluded. Only thirty questionnaires
were used for further analysis, which gave a total of 50% response rate.
The socio-demographic data of the respondents were tabulated in Table 3.1 which comprise of gender, ethnic, age, and salary
range. 97% of the respondents were Malay while only 3% of the respondents were non-Malay. The distributions of male to female
respondents were 33% and 67% respectively. The majority of the respondents were aged between 51 to 60 years old which
comprises of 54% of the total respondents while only one respondent was aged at 40 years old (3%). The other 43% of the
respondents were aged between 41 to 50 years old (30%) and above 61 years old (13%). Also, 47% of the respondents earn betwee n
RM 4501 and above per month, followed by both RM 1501-3000 (20%) and less than RM 1500 (20%) per month, while 13% of the
respondents that have the frequency of 4 earns between RM 3001-4500 per month.
Table 3.1: Socio-demographic characteristics of the respondents
Demographic data
Percentage (%)
40 years old
41 to 50 years old
51 to 60 years old
61 years old and above
RM1501 to 3000
RM3001 to 4500
RM4501 and above
3.2 Quality of Vision, Wearing Hours and Symptoms Reported and Total Satisfaction of PALs wearers.
Based on initial assessment, all of the respondents have healthy eyes with normal corrected vision. Hence, high qualities of vision and
high levels of patients satisfaction were most appreciated after the prescription of the progressive additional lens (PALs). The
feedbacks from the respondents were assessed based on two key factors, which were the quality of vision at the different viewing
area and the symptoms reported after the application of PALs. Figure 3.1 and Figure 3.2 shows the mean for the quality of vision at
the different viewing area, and the mean value for symptoms reported related to the use of progressive additional lens respectively.
Figure 3.1 Mean quality of vision at the different viewing area.
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Figure 3.2 Mean symptoms reported associated with PALs.
The mean value provided is directly proportional to the satisfaction value. The highest mean for quality of vision (Figure 3.1)
reported by the respondents is by seeing grocery shelves at intermediate viewing (7.27±1.84), followed by seeing keyboard
computer at near (7.20±2.02), seeing computer monitor at intermediate viewing (7.07±2.05), seeing signboard at distance
viewing (7.03±1.85), reading paper on a chair (6.97±2.19), reading book at table (6.93±2.16) .The lowest quality of vision
reported is by viewing at a distance while driving (6.67±2.45). The descriptive result of wearing hours shows that the mean is
9.47 ± 5.698 hours. These high wearing hours indicates that most of the PALs wearer wore it for almost half of their day to do
their daily activities.
In contrast, the mean value provided by the symptoms is indirectly proportional towards the satisfaction value. The highest
reported symptoms related to the use of PALs lenses were blurry vision with a mean of 7.07±2.60, followed by eye strain
(7.27±2.55), dizziness (7.33±2.86) and headache (7.47±2.93). A high mean value for the symptoms is because; most of the
patients rate their symptoms as „10. The value 10 indicates that none of the symptoms to be felt by the patients.
3.2 Correlation of Quality of Vision, Symptoms with Total Satisfaction Level of PALs Wearer.
The relationship between the quality of vision at the different viewing area and the total satisfaction were obtained by using
Spearman Correlation. The test revealed that the correlation between the quality of vision for driving and seeing signboard at a
distance is positively correlated with the total satisfaction, and both were statistically significant, having the value of p<0.05
(Figure 3.3 (A) and (B)). Out of 10 questions regarding the quality of vision, the correlation of quality of vision during driving
showed the lowest in the ranking of total satisfaction.
Figure 3.3: Scatter plot of correlation between qualities of vision at a distance with total satisfaction. (A) Correlation between qualities of
vision of driving with total satisfaction (B) Correlation between qualities of vision of seeing a signboard with total satisfaction.
Figure 3.4: Scatter plot of correlation between qualities of vision at intermediate with total satisfaction. (A) Correlation between qualities of
vision of seeing computer monitor with total satisfaction (B) Correlation between qualities of vision of seeing grocery shelves with total
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The correlation between the quality of vision at the intermediate viewing for seeing computer monitor and seeing grocery shelves
are highly correlated to the total satisfaction Figure 3.4 (A) and (B). Higher total satisfaction was associated with higher level of quality
of vision. Higher scores indicated a better clarity of the visual performance. The correlation between the quality of vision and total
satisfaction is the highest at intermediate viewing compared to others.
The correlation between the quality of vision at near viewing for seeing computer keyboard, reading paper while sitting on a chair
and reading a book on a table, are highly correlated to the total satisfaction, and it is statistically significant to each o ther as shown in
Figure 3.5 (A), (B) and (C). The highest quality of vision was seeing computer keyboard, followed by reading the paper on a chair and
reading a book at the table. Table 3.2 summarises the correlation of the quality of vision with their respective satisfaction values.
Figure 3.5: Scatter plot of correlation between qualities of vision at near with total satisfaction. (A) Correlation between qualities of vision of
seeing computer keyboard with total satisfaction (B) Correlation between qualities of vision of reading the paper at the chair with total
satisfaction. (C) Correlation between qualities of vision of reading book at a table with total satisfaction.
Table 3.2: Summary on the correlation of quality of vision at distance, intermediate, and near regards with the tasks required.
Quality of Vision
Regression (r)
p value
At Distance
See signboard
At Intermediate
See computer monitor
See Grocery shelves
Reading books
Reading paper at chair
See keyboard
There was a statistically significant difference of the correlation between each symptom and their total satisfaction, which was
analysed by Spearman Correlation. The mean rating for each symptom in the questionnaire did not appear to differ between
each other. The correlation between the symptoms and satisfaction value were shown in Figure 3.6 and Table 3.3.
Table 3.3: Summary on the correlation of the symptoms.
Regression (r)
p value
Eye strain
Blurry vision
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Figure 3.6 Scatter plots of associated symptoms with total satisfaction. (a) Headache with total satisfaction, (b) Eyestrain with total
satisfaction, (c) Blurred vision with total satisfaction and (d) Dizziness with total satisfaction
4.0 Discussion
4.1 Quality of Vision at Total Satisfaction.
Linear regression was performed to determine the correlation between the qualities of vision with the total satisfaction (Figure 3.4 and
3.5). Slopes of the regression lines are positive with the increase in score of the total satisfaction for each of the task. As for the
relationship between the qualities of vision with their total satisfaction level and the results of the Spearman rank correlation test, it
shows that the quality of vision was significantly correlated with the patient satisfaction. It can be said that different viewing area or
different tasks to be a major factor that affects the satisfaction level as people seek for best correction lenses to help in improving their
visual acuity and improving their quality of life.
Measuring the variances at different viewing areas has proven to affect the visual task performance (J. Sheedy, Hardy, & Hayes,
2006). Hence, patients should be aware that, different zones widths and areas across the lens were designed to satisfy their visual
performances. The result shows that the level of visual satisfaction was highest at the intermediate as compared to the distance and
the near viewing. The correlation between these qualities of vision at intermediate viewing with total satisfaction gave the highest
correlation regression as shown in Table 3.2. The tasks that require the respondents to use their lens in the intermediate zones also
show positive linear regression line and higher correlation coefficient value. This corroborates with Gispets et al., (2011) and Spencer
& Ciuffreda, (2002) where the stimulus becomes sufficiently cramp and precise to be felt within the clear field of the view at the
intermediate channel. This will reduce the shift of the head movements and cause it to become a more desirable yet closer match to
the normal eye fixation magnitudes (J. E. Sheedy, 2004). Moreover, depth-of-focus in this area offers a better compromise in which
sharper retinal images produced to be corresponding with the objects. Interestingly, related to this, it was reported that the
performance of PALs is equivalent to the performance of single vision lenses (Spencer & Ciuffreda, 2002). The intermediate vi ewing
provides a clear vision non-stepwise and corresponds to the wide visual distance range. It greatly enhances the capacity of the visual
field at that segment (Sugarman, 1994). Nonetheless, the main consideration of the PALs effectiveness at the intermediate viewing
needs to be related to the task itself.
The result of high satisfaction with significant positive linear correlation was also found at the near viewing on the tasks like
reading a book on the table, reading the paper on a chair and seeing the keyboard (Figure 3.5). During reading, the eye does not
move in an orderly manner. They pause, move backwards and jump from one point to another; hence require a high level of
accommodation (Batemanazan et al., 2014). These findings support the prediction by the previous studies where reading involving
size print would require the use of the clearest portion of the lens and the clarity of vision is ideal at the centre of the near zone (Lynn,
1998). However, this was contradicted by the study done by Gime, (2008), the distance vision tasks have higher satisfaction, but for
near vision, the task received the lowest score.
High satisfaction can be barely assumed as most wearers were either able to tolerate well with the eye movement required during
near task or adapt on the preferred lens design. This may happen due to the choices of the lens design for the suitable daily task were
more toward near tasks compared to distance tasks (R.Cited, 2004). However, according to Chu, (2010), PALs wearer require a
significantly higher head movements when reading a near text which diminished the adaptation and satisfaction level of the PALs
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wearers. Hence, it contradicted with the result gathered in this study due to the different type of statistical analysis used which is an
analysis of variance (ANOVA).
At the distance viewing, the result shows the lowest level of visual satisfaction as both require higher visual demands such as
driving and seeing signboard (Figure 3.3 (a) and (b)). During driving, by viewing an object at a distance paired with vision disturbance;
peripheral blur, unwanted astigmatism and distortion. Han et al. (2011) reported that progressive additional lens (PALs) wearer was
more satisfied as compared to the use bifocal lens. However, most of them were uncomfortable with distortion at the peripheral vision.
A study conducted by Ellison, (2012) justified the same effect on PALs wearers. Activities such as driving or walking by using
progressive additional lens cause the vision to appear to oscillate at the sides. This scenario rose due to the aberration and unwanted
astigmatism at the peripheral section of the lens while making the higher visual demand (Spencer & Ciuffreda, 2002). Peripheral
astigmatism in the progressive lens has been found to be significant in its axis and magnitude (Hendicott, 2007). This periph eral
astigmatism can change the power along the vertex line of the PALs progression. Thus wearers may experience astigmatism with the
occurrence of blur when the eye moves toward the other different viewing areas.
4.2 Symptoms and Total Satisfaction
Most PALs wearers reported being comfortable with their lenses as the data obtained shows the least of complaints and symptoms
with the high level of satisfaction. Blurry of vision is the most noticeable symptom that lowered the level of total satisfac tion and shows
the most positive regression lines among others (Figure 3.6). Poor adaptation, changes of power profile in term of magnification,
astigmatism or aberration along the PALs lines can be the main causes of blurry vision. A similar result is obtained from the quality of
vision at distance viewing which shows the lowest satisfaction. This likely due to the optical design of the PALs as progressive
additional lens require gradual changes of distance to near area which caused unwanted distortion through the lower lens periphery
(Chu, 2010). However, there were no significant differences between the symptoms. Also, a high correlation was recorded between
the symptoms reported with the total satisfaction (0.7 and above) with the PALs dispensed. This indicates most wearer can use their
PALs without any significant visual problems in their daily activities.
5.0 Conclusion
Despite their limitation, progressive additional lenses are the best option and represent the rigid multifocal correction for a large share
of the presbyopic population. Even though it had been introduced to the public many years ago; approximately 40 years, however, the
improvement of the PALs design are consistently released as there was always a high demand for needs of the better understanding
towards its progressive surface (Pope, 2000). The improvements are used to enhance the antagonist lenses qualities together with
wearers adaptation and happiness. Thus, the result from this study can benefit all eye-care practitioners especially optometrists to
improve the quality of servicing progressive additional lens by providing the information regarding the quality of vision that is positively
correlated with the level of total satisfaction for progressive addition lenses delivered by UiTM Vision Care. It is reasonable for the
quality of vision at a different area or different tasks to be major factors that affect patient satisfaction level because wearers seek the
best correction to help to improve the visual acuity and their quality of life.
The eye-care practitioners should aware of the PALs wearers priority and requirements in selecting the appropriate lens design
that matches with the tasks required. Hence, the study can act as a stimulus for better research in the future especially in ophthalmic
industry to develop and market PAL designs based on the wearers specific visual needs and tasks. Additionally, by time to time, due
to advance in technology, there will be some improvement in PALs designs, potentially reducing the possibility of symptoms, hence
increasing satisfaction level among PALs wearers in the future.
The authors wish to thank UiTM Vision Care and Faculty of Health Sciences, Universiti Teknologi MARA (UiTM) for
permission to conduct the study and to all participants in the study.
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... 32,33 Appropriate selection and glazing are specifically important with PALs, which present many variables that can lead to patient dissatisfaction, hence influencing the overall quality of vision. 34,35,36,37 The ability to specify progressive corridor length requires the practitioner to possess an in-depth understanding of the interplay between the natural reading-level preferences of eyes, lens fitting parameters, individual prescription values and the design goals of the lens itself. 11,38 Checking and verification for finished spectacle PALs is an important routine that ensures quality control and enhances patient satisfaction and comfort. ...
... Furthermore, complaints had different effects on overall satisfaction. Similar results were reported by Najmee et al. 34 who found that the quality of vision was positively correlated with the level of total satisfaction for PAL and inversely correlated with the reported complaints. However, blurry vision was the most prominent complaint that reduced the level of total satisfaction. ...
... Besides their popularity and the fact that they do seem to improve wearers' quality of life [Ahmad Najmee et al., 2017], not everyone gets used to them. Scientific literature is scarce when it comes to gathering knowledge about why few "rookie" wearers suffer in adapting to these lenses or which could be the main factors contributing to this. ...
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For decades, manufacturers have attempted to reduce or eliminate the optical aberrations that appear on the progressive addition lens' surfaces during manufacturing. Besides every effort made, some of these distortions are inevitable given how lenses are fabricated, where in fact, astigmatism appears on the surface and cannot be entirely removed or where non-uniform magnification becomes inherent to the power change across the lens. Some presbyopes may refer to certain discomfort when wearing these lenses for the first time, and a subset of them might never adapt. Developing, prototyping, testing and purveying those lenses into the market come at a cost, which is usually reflected in the retail price. This study aims to test the feasibility of virtual reality for testing customers' satisfaction with these lenses, even before getting them onto production. VR offers a controlled environment where different parameters affecting progressive lens comforts, such as distortions, image displacement or optical blurring, can be analysed separately. In this study, the focus was set on the distortions and image displacement, not taking blur into account. Behavioural changes (head and eye movements) were recorded using the built-in eye tracker. Participants were significantly more displeased in the presence of highly distorted lens simulations. In addition, a gradient boosting regressor was fitted to the data, so predictors of discomfort could be unveiled, and ratings could be predicted without performing additional measurements.
... The majority of presbyopes are prescribed PALs, which are most optically complex, followed by bifocal or trifocal spectacles. 2 The PALs have a vertical gradient of increasing power toward the lower part such that the wearer can see at all distances by looking through different parts of the lens. Although PALs are widely used, they do not work for everyone. ...
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Progressive addition lenses introduce distortions in the peripheral visual field that alter both form and motion perception. Here we seek to understand how our peripheral visual field adapts to complex distortions. The adaptation was induced across the visual field by geometrically skewed image sequences, and aftereffects were measured via changes in perception of the double-drift illusion. The double-drift or curveball stimulus contains both local and object motion. Therefore, the aftereffects induced by geometrical distortions might be indicative of how this adaptation interacts with the local and object motion signals. In the absence of the local motion components, the adaptation to skewness modified the perceived trajectory of object motion in the opposite direction of the adaptation stimulus skew. This effect demonstrates that the environment can also tune perceived object trajectories. Testing with the full double-drift stimulus, adaptation to a skew in the opposite direction to the local motion component induced a change in perception, reducing the illusion magnitude (when the stimulus was presented on the right side of the screen. A non-statistically significant shift, when stimuli were on the left side). However, adaptation to the other orientation resulted in no change in the strength of the double-drift illusion (for both stimuli locations). Thus, it seems that the adaptor's orientation and the motion statistics of the stimulus jointly define the perception of the measured aftereffect. In conclusion, not only size, contrast or drifting speed affects the double-drift illusion, but also adaptation to image distortions.
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This paper deals with the modern trends in typhlotechnics in terms of quality of life for persons with visual impairment. A person with visual impairment is strongly influenced by the development of modern technologies. From the perspective of special education the support of people with visual impairment should take place not only by using the typhlotechnics, artificially made aids, but activity of the individual is equally important. The main method for the outputs of our paper selected was the analysis of foreign and local literature, mostly from the years 2008-2014. Comparison of specialized material allows the evaluation of the current state of development in the area and creation of an informational base for further research projects.
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During the process of reading, the eyes do not move continuously but jump from one word to another, and they also stop at particular points. In eye-tracking studies, these processes are called „saccade‟ and „fixation‟. This paper presents an analysis of the reading patterns of readers reading Malay and English sentences and questions using the eye tracker. Malay-English bilingual readers read a set of statements in Malay and English and their reading comprehension was tested using questions with different levels of difficulty. Their correct responses and reactions to the comprehension questions are also presented and discussed in this paper.
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Presbyopia is one of the earliest universal signs of aging and the basic pathophysiology involved in its development has been a matter of controversy for centuries. This article discusses many aspects of presbyopia by reviewing the literature on the multitude of age-related changes that occur in the eye.
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Background Multifocal glasses (bifocals, trifocals, and progressives) increase the risk of falling in elderly people, but how they do so is unclear. To explain why glasses with progressive addition lenses increase the risk of falls and whether this can be attributed to false projection, this study aimed to 1) map the prismatic displacement of a progressive lens, and 2) test whether this displacement impaired reaction time and accuracy. Methods The reaction times of healthy ≥75-year-olds (31 participants) were measured when grasping for a bar and touching a black line. Participants performed each test twice, wearing their progressives and new, matched single vision (distance) glasses in random order. The line and bar targets were positioned according to the maximum and minimum prismatic displacement effect through the progressive lens, mapped using a focimeter. Results Progressive spectacle lenses have large areas of prismatic displacement in the central visual axis and edges. Reaction time was faster for progressives compared with single vision glasses with a centrally-placed horizontal grab bar (mean difference 101 ms, P=0.011 [repeated measures analysis]) and a horizontal black line placed 300 mm below center (mean difference 80 ms, P=0.007). There was no difference in accuracy between the two types of glasses. Conclusion Older people appear to adapt to the false projection of progressives in the central visual axis. This adaptation means that swapping to new glasses or a large change in prescription may lead to a fall. Frequently updating glasses may be more beneficial.
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Art gallery exhibition area is a place to display the ideas of artists for visitors through the visual quality toward the artworks display. This paper seeks to present the findings of a human visual factor towards the artworks from the literature review which then tested by an observation survey at Solaris Dutamas in Kuala Lumpur. The experts’ interview is part of the research process aimed in to strengthen data from the literature review. Qualitative methodology is apply to gather and analyze data collection. The findings revealed the visible factors affect the human visual quality. These factors can be categorized into 3 components.
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Purpose: A longitudinal prospective, cross-over, double masked study was designed to evaluate task oriented visual satisfaction and wearing success with two types of simultaneous vision multifocal soft contact lenses. Methods: Twenty-two presbyopic subjects followed two 14-day trial periods in which they were alternatively and randomly fitted with two types of multifocal lenses. Habitual tasks were described in terms of observation distance, visual demand level and time allocation. Subjects graded visual satisfaction with each pair of lenses and each habitual task at different times during each trial. Overall satisfaction was evaluated after completion of the two trial periods. Wearing success was determined by the percentage of subjects opting to continue multifocal lens wear and by the number of subjects still wearing their lenses six months later. Results: Viewing distance and visual demand level were found to influence visual satisfaction (p
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Purpose: To introduce a simple method for subjective perception of progressive addition lens (PAL) peripheral image blur (PIB). The amounts of PIB induced by traditional PAL trial lenses (plano distant PAL, TPAL) and prescription PAL (FPAL) were also evaluated. Methods: Subjects wearing the PALs adjusted their heads laterally to view the fixation target for PIB perception. 38 subjects were randomized and recruited from the Eye’ni optical shop. Outcomes were assessed by the high-contrast visual acuity chart (LogMAR scale), and by subjectively indicating the magnitude of PIB on a scale of 0 to 10 (10 is extremely blur) using astigmatism-sensitive optotype (Polatest®, Carl Zeiss Vision, Germany). Results: Visual acuities (mean ± SD) at the central and temporal fixations were measured at 0 ± 0.03 and 0.2 ± 0.04 with FPAL, and 0 ± 0.03 and 0.1 ± 0.03 with TPAL respectively. Significantly lower visual acuities were found with the temporal fixation than with the central fixation in both PALs (p
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Background. There is limited research conducted on uncorrected refractive errors, presbyopia, and spectacles use among the elderly population in residential care in developing countries such as India. We conducted a cross-sectional study among elderly in residential care to assess the spectacle coverage and spectacles usage in the south Indian state of Andhra Pradesh. Methods. All 524 residents in the 26 “homes for aged” institutions in the district were enumerated. Eye examination was performed that included visual acuity (VA) assessment for distant and near vision. A questionnaire was used to collect information on spectacles use. Results. 494/524 individuals were examined, 78% were women, and 72% had no education. The mean age of participants was 70 years. The spectacle coverage for refractive errors was 35.1% and 23.9% for presbyopia. The prevalence of current use and past use of spectacles was 38.5% (95% CI: 34.2–42.8; n = 190) and 17.2% (95% CI: 13.9–42.8), respectively. Conclusions. There is low spectacle coverage for both refractive errors and presbyopia among elderly individuals in residential care in the south Indian state of Andhra Pradesh. Appropriate service delivery systems should be developed to reach out this vulnerable group of seniors on a priority basis.
This paper focuses on the design, fabrication, and metrology technologies of the ultra-precision optical freeform surface for progressive addition lens (PAL). The PAL, which has a front surface with far-view zone, near-view zone, and intermediate zone, was used to remedy presbyopia by distributing optical powers of the three zones. The PAL surface is a freeform surface because of its non-symmetrical power distribution. We introduce the PAL freeform surface design methodologies, including B-spline description and its optimization. After optimization of B-spline parameters of the PAL surface, we demonstrate the fabrication and measurement technologies of the mold for PAL surface by using ultra-precision freeform machining machine with slow tool servo function and ultra-precision 3D metrology system with user-defined function.
In a subjective preference study, two key progressive addition lens parameters, near zone width and corridor length, were varied in a double-masked, randomized, clinical trial of 49 patients. Each subject received a complete eye examination and a new frame. Each wore 6 pairs of lenses for one week at a time and completed questionnaires relating to vision, adaptation, and satisfaction. The preferred lens was identified from the three near zone width lenses and from the three corridor length lenses. Patient characteristics were analyzed for their effect on design preference. Satisfaction ratings following a brief experience with each design were compared to ratings after one week of wear in order to ascertain the predictability of initial impressions. One lens design appeared twice in the preference trial, providing an assessment of the repeatability of the rating instrument. The lens design with the widest near zone was rated significantly lower than the other near zone width designs for nearly every question relating to vision, adaptation, and satisfaction. This lens was also least preferred of all the designs. Preferences for corridor length were evenly distributed among the three designs. Of patient characteristics, years of progressive addition lens wear and gender significantly affected design preference in this population. Initial impressions were not predictive of satisfaction after a week of wear. The rating instrument was judged to have low repeatability. In the head movement portion of the study, 18 participants from the preference study wore the three near zone width designs while reading three paragraphs of varying print size. From a 20 second recording for each of three different paragraphs with each lens, measures of head rotation and posture were collected. The amplitude of head rotation was significantly affected by print size but not by lens design. The effective zone widths on the lenses scanned by the eyes and the locations of the reading levels were calculated from the head rotation and posture data. Effective zone widths were narrower than the contour plot widths for each condition.