iPhone Icons and Age-Related Decline of the Visual Sensory System
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Running Head: IPHONE ICONS & AGE-RELATED DECLINE OF VISION 1
iPhone Icons and Age-Related Decline of the Visual Sensory System
Armen J. Chakmakjian
Bentley University
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 2
Abstract
This paper is an expert review of the current implementation of icons on mobile
interfaces, especially the iPhone against the backdrop of customers with declining visual
perception. The paper starts by describing the current understanding of the first two stages of the
human visual sensory system, the eye and the lateral geniculate nucleus. The research then
describes the decline of the healthy visual system related to advancing age in the areas of image
size, contrast sensitivity and decline in the ability to distinguish hue, saturation and brightness.
The paper then reviews the relevant research about icons and in particular mobile phone
iconography against the age-related decline in the visual sensory system. In particular, the paper
looks at the affect of “retina” displays such as on the newest iPhone to see if they may be
exacerbating the visual difficulties of older users. The conclusion is that the iPhone designers are
not taking into account the needs of older users with the current model of accessibility. The
recommendation in this paper is for Apple to create a mode where the icons are quadrupled in
size to accommodate age-related decline in size, contrast sensitivity, and color discrimination.
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 3
iPhone Icons and Age-related Decline of the Visual Sensory System
Perception is a multi-stage signal-processing event in which external stimuli are
processed in order to form an integrated cognitive representation that can be used for decision-
making. (Gazzanina, Ivry, & Mangun, 2002, p. 148). Vision is one of the biological channel
through which a set of signals is consumed. This paper deals with the initial stages of visual
sensory system, which are key in detecting a stimulus, and the specific biology that is used to
process light signals for later use in cognitive functions.
Modern technology provides us with an interesting new set of inputs in the form of
display technology for our visual sensory adaptations to process that are not found in the natural
environment. Display technology has now achieved a pixel resolution such found on the Apple’s
iPhone “retina” display reaching 1136-by-640-pixel resolution at 326 ppi. (Poor, 2012) The
human eye is measured in pixels per degree of visual angle, meaning proximity of the object of
interest affects this measurement. As one NASA report points out, this is about 120 pixels per
degree at 100% contrast, or a rough maximum of 350 ppi for those blessed with astronaut vision.
(Gille, Martin, Larimer, 1996) This clarity of resolution allows for vibrant and very dense
graphical information to be displayed.
Concurrently, many users with healthy eyesight are experiencing the expected age-related
decline of their visual sensory system. They have difficulty focusing on small objects; their
contrast sensitivity decreases and their ability to discern visual properties such as hue, brightness
and saturation also decline. Software and mobile manufacturers are creating more and more
precise detail on mobile display and a particular feature of iOS is the concept of folders. Folders
allow the grouping of several related icons within the space of a normal icon. This shrinking of
visual information may create a problem for users as they age.
This paper describes the visual sensory system from both a biological and signal theory
point of view, and reviews the relevant research in age-related factors that affect the visual
sensory system. A description of iconography on the iPhone and the new folder feature follows.
The paper concludes with a suggestion that is not currently employed in the accessibility
accommodation features in iOS.
The Visual Sensory System
The visual sensory system has 4 basic stages: the eye itself, including the lens and retina
systems, the lateral geniculate nucleus (LGN), the visual cortex, and then the rest of brain’s
cognitive processing on the visual image. The focus of this paper is on the eye and the lateral
geniculate nucleus and the age related decline therein. Figure 1 illustrates the eye and its two
basic subsystems. The lens is a flexible combination of collagen and epithelium (Werner,
Peterzell, & Scheetz, 1990) attached to a muscle that flexes the lens to focus an image on the
retina. Lens flexibility is maintained because of a water-soluble protein embedded in it, a-
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 4
crystallin. (Heys, Cram, & Truscott, 2004)
Figure 1: Stages of the Visual Sensory System
The retina is made up of a distribution of neurological photoreceptors each containing
light sensitive molecules called photopigments. (Gazzanina, Ivry, & Mangun, 2002, p. 150)
These receptors, called cones and rods, detect color and brightness of objects respectively.
(Cornsweet, 1970, p. 90) Cones, which are predominantly in the fovea at the center of the retina,
concentrate on color and are organized as red, yellow and blue receptors that pass along color
signals to the next stage of the visual system. From a quantitative point of view, they are actually
short, medium and long wavelength-sensitive receptors and organized into a pattern so that a
“single class of cone samples the retinal image.” (Roorda, 1999, pp. 520-2) The Roorda study of
the distribution of the medium and long receptor cones has implications on variation in color
sensitivity, one manifestation of which is the well-understood condition of color blindness. Rods
concentrate on brightness of objects and tend to be concentrated around but away from the fovea.
Cones and rods pass their respective information along to the lateral geniculate nucleus
that can be thought of as a filter. Research done by Kaplan, Purpura and Shapley shows that the
LGN introduces noise in the signals it receives from the eye and speculates that this adaptation
preconditions the signal before sending it along to the visual cortex to avoid premature saturation
in the cortex before it combines the signals to create a cognitive image. (Kaplan, Purpura, &
Shapley, 1986)
A discussion of signal theory is necessary to complete the concept that Kaplan puts
forward. One excellent definition of a signal is “A signal can be defined as the variation of a
quantity by which information is conveyed regarding the state, the characteristics, the
composition, the trajectory, the course of action or the intention of the signal source. A signal is a
means to convey information.” (Vaseghi, 2000). At each stage, the visual sensory system detects,
filters and refines the light signal emanating from an object. Light is broken up by color and
luminance into signals that are sent to the brain for cognitive processing. Just as in electrical
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 5
signal theory, anything that attenuates a light signal or introduces or filters noise as it passes
through the various stages of the visual sensory system is doing signal processing.
Visual Sensory System and Age-Related Decline in Property Sensitivities
The ability of the visual system to detect contrast is an adaptation that allows a human to
detect the edges of an object and separate that object from its surroundings for processing. The
general definition of contrast is (Lmax – Lmin)/(Lmax + Lmin) where L is the measure of
luminance. (Arden, 1978) This is the ratio of the difference in luminance between 2 regions and
the sum of the luminance of the two regions. Depending on the sensitivity of the individual, if the
difference is small, the contrast may not be detectable. Cones themselves do not easily detect
brightness; it is the job of the rods to help with this function. Comparisons of test results over
time come back with the same data, that contrast sensitivity is relatively stable until the age of 65,
and deteriorates after that. (Werner, Peterzell, & Scheetz, 1990)
Contrast sensitivity can be affected by texture differences between the object and its
background. Basic contrast sensitivity, often referred to as first-order stimuli sensitivity, deals
with luminance differences between foreground and background. Second-order stimuli, texture
differences between the foreground and background, allow for further detection and recognition
of the edges of objects. A 2009 study points out that both contrast sensitivity for first-order and
second-order stimuli does show a progressive decline with age and in fact sensitivity to second-
order stimuli may actually begin declining earlier than first-order sensitivity. (Tang & Zhou,
2009) To illustrate this example, consider an object that has a crosshatch pattern that appears as
texture, but the background is smooth, over time, the secondary aid in detection diminishes in
influence faster than the simple contrast between the objects.
The perception of color has 3 distinct factors: hue, saturation and brightness. Hue is,
quantitatively for this discussion, the wavelength of light that is detected by the visual system.
(Cornsweet, 1970, p. 224). In a 2001 NIH sponsored study, it was found that age-related
deterioration seemed to happen with Medium and Long cone sensitivity rather than with short
cone sensitivity after the age of 65. (Shinomori, Schefrin, & Werner, 2001) This has large
implications since it means that after the age of 65 it can be increasingly difficult to see red and
green. Simultaneously, a loss in the ability to distinguish blue begins to occur in old age also
because of yellowing that occurs in the lens. This yellowing blocks blue from getting to the blue
cones (S cones). (Jackson & Owsley, 2003)
Brightness is a measure of variation of intensity of the light source detected by the visual
system. (Cornsweet, 1970, p. 225) As a 1990 study points out, there are 2 factors that affect the
transmission of light through the eye as a person ages. These are crystalline lens absorption and
pupil size. The lens gets stiffer and thicker as humans age which both affects focus of the light on
the retina, as well as the amount of light that passes through. The pupil will shrink slightly with
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 6
age and will alter the quantity of stimulus reaching the retina, the culprit being the aging iris.
Color discrimination may also be affected by the amount of light reaching the fovea. (Werner,
Peterzell, & Scheetz, 1990)
Saturation is a measure of how much white light is mixed in with a monochromatic hue.
It tends to vary with brightness. (Cornsweet, 1970, p. 225) This paper does not address age-
related saturation detection with respect to the use of icons in smartphones.
As the Werner article points out, other studies show the decline in the performance of the
LGN correlating to declines of up to 50% in neurons in the visual cortex in the elderly. (Werner,
Peterzell, & Scheetz, 1990) This paper will not address those changes and effects.
Iconography on the iPhone and the Elderly
Icons in computing were invented in the Xerox PARC designs that Apple consumed into
the Macintosh. Icons allow a user to start a task or open a file from a pictorial representation
instead of selecting an action from from a list of files and typing in the request on command line
interface. Icons take advantage of several properties of the underlying graphical system in order
to communicate with the user. They are made up of visual details of the normal computing
display environment, and might try to communicate the function behind the future action if
selected. (Leung, McGrenere, & Graf, 2009)
.
Figure 2: Spatial Frequency versus Contrast Sensitivity Curves taken for different age groups (McGrath & Morrison, 1981)
Since contrast sensitivity is directly correlated with the difference between background
and foreground, it would be no wonder that if the user had a background image was not uniform
in color and different from the icon which is emblazoned on it, a user with declining contrast
sensitivity might have trouble discerning an icon from its background. A study on spatial
frequency versus contrast sensitivity (McGrath & Morrison, 1981) tells us that as people age their
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 7
peak sensitivity to spatial frequency (the ability to discern fine detail in a high contrast
environment) was unchanged, but their contrast sensitivity was degraded. Figure 2 shows us the
detail of their experimentation. It can be extrapolated here that as long as the background image
of the icon screens of a phone are bright and neutral, this can mitigate the effects of the decline in
contrast sensitivity.
Size of icons is a significant factor in detection and the ability to perform tasks on the
iPhone for the elderly. One study shows that the symbol size of the icon is critical in recognizing
the icon, and leads to increased time to find the specific icon of interest. (Mertens, Brandl,
Przybysz, Koch-Körfges, & Schlick, 2012) The standard size of an iPhone 5 icon is 114x114
pixels (Apple Inc., 2012) which is roughly 9mm. A year 2000 study showed that people with
deteriorating vision were 50 times slower in selecting icons sized at 9.2mm than the fully-sighted.
(Jacko, Rosa, Jr., Scott, Pappas, & Dixon, 2000)
While the normal iPhone icons themselves may cause some difficulty, a greater problem
may have been introduced by Apple in their zeal to allow people to group similar icons together.
Apple’s icon folder function allows a user to press on an icon, and then drag it onto other icon.
The system responds by creating an icon-sized container, with miniature versions of the original
icons inside it. A tap on that container opens up a drawer that shows the user the full-sized icons
contained in the folder. The problem here is that the with the decline in the ability of the lens to
flex sufficiently to focus on small objects, the extremely small icons within a folder icon may not
be focusable at all for an elderly user.
Figure 3: Typical iPhone 4 display showing icons and folder icons.
Figure 3 shows a typical iPhone 4 display with icons and folders. Up to 9 icons are
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 8
shrunk within a folder icon the size of a standard icon. That means that each shrunken icon is
slightly less than 1/3 of the regular icon size (less because there is a space between them), less
that 3mm. While the separation of the tiny icons is done on a black background, heightening
contrast, the details on each icon are now potentially so small that a typical user with declining
ability may no longer be able to detect detail except for icon color.
With the decline in contrast sensitivity and hue sensitivity from the red/green spectrum as
previously discussed, one could posit that differentiating certain icons on a non-black or non-
white background might be impossible for a elderly user, including the small red alert circle some
icons will put up on their top right corner (See Figure 3). Compounding this, the yellowing of the
lens blocks blue light from reaching the fovea, making it so that the ubiquitous use of blue may
be a problem. The example of the Skype icon in Figure 3, if the reader can find it, will be a
typical problem for the older user. The blue Skype icon within the folder would be almost
unrecognizable in this case because of the elderly user’s diminished ability to focus, their ability
to discern hue, and diminished contrast sensitivity. The blue S symbol might be seen as yellow on
the white background which may not be enough contrast. All the user might see is a small yellow
blob on black. Further examining Figure 3, when a bluish icon is full sized, such as the Dropbox
icon, it is also accompanied by white text below it. If the user has a dark background, the white
text might be visible. However, the text is quite small in this case, and any decline in contrast
sensitivity combined with a light background might make this apparent textual accommodation
less than useful.
Recommendation
The major recommendation in this paper is due to the lack of serious accommodations on
the iPhone for the elderly. There are some accommodations including auditory feedback that can
be invoked, but the auditory system for the elderly is also in decline at the same time. Apple
should create a mode where 4x sized icons (meaning 18mm x 18mm) icons and folders are used.
Given the brightness of the display this would mitigate many of the problems introduced by
aging, including inability to focus on small objects and diminished contrast sensitivity.
Conclusion
This study began by describing visual perception as a concept of signal theory and
concentrated on the first two stages of the visual sensory system. These two stages detect and
transform light and color into signals that are used later in cognitive functioning. The paper then
described the properties of visual perception, object size and the ability of the lens to focus the
image on the retina. A description of how the retina receptors, cones and rods, detect light
patterns to discern contrast, hue, brightness and saturation followed. A survey of research then
pointed to how the sensitivity to these properties decline with age. The paper studied specific
feature of the iPhone, application icons and icon folders and the problems in detection and
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 9
discernment in older individuals. Research showed that the usability of the iPhone through its
primary interface might become challenging to elderly users. Finally the paper makes a simple
recommendation to accommodate the elderly by altering the size of icons.
IPHONE ICONS & AGE-RELATED DECLINE OF VISION 10
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