At present,
there are four primary causes of visual impairment in older
people: cataracts, glaucoma, diabetic retinopathy and age-related
macular degeneration. Although there are many other types
of visual disorders, these affect the large majority of the
population.
The “Big 4”: (clockwise from
upper left) cataract, glaucoma, diabetic retinopathy, age-related
macular degeneration.
Although
there have been very important developments in the surgical
and medical treatments of these conditions, there are still
a significant number of unresolved problems in the assessment
of vision before, during, and after these interventions. There
is much left to learn about residual vision and its amenability
to rehabilitation. More often than not, even after all possible
treatment have been tried, the individual is still left with
a significant reduction in vision. The challenge is to examine
how the sensory, perceptual, and psychosocial components of
visual impairments may be studied to bring about better understanding
of the system as well as more comprehensive treatment of people
who experience visual loss.
Sensory Capacities
of an Impaired Visual System
When
a person experiences visual loss, it rarely results in total
blindness. One of the first goals is to appropriately assess
the remaining capacity of the sensory system. Applied psychophysics
offers the opportunity to expand our knowledge of sometimes
difficult to quantify residual vision.
Test of Vernier Acuity (top) and
Spatial Contrast Sensitivity (bottom)
Perceptual
Abilities and
Readaptation to Visual Loss
Once the
sensory capacity of the visual system has been assessed, the
next question centers on how well the person uses the remaining
vision that he or she has. This encompasses the unaided use
of perceptual and cognitive abilities to make sense of the
world (Figure 3) and the additional challenges posed by the
necessity for optical or electronic devices.
It has been
shown that a person’s use of residual vision can improve
substantially following practice and training. The challenge
remains to design training programs which are efficient, cost-effective,
and are quantifiable in terms of their results.
The (incorrect) interpretation of
salient features of a visual stimulus.
Psychosocial
Impact of Visual Impairment
Finally,
it has been said that visual impairment is a “social
disease”, which is to say that it does not only affect
the individual who loses vision. His/her family, friends,
and larger social milieu is also affected by the process and,
therefore, must be involved in the restoration of function
to the individual. People often find it difficult to discuss
or even admit that they have a visual problem. They often
believe that they are the only ones who have to deal with
this type of situation.
Studies
are ongoing to examine the broader affect of visual loss on
the significant others of visually impaired people and on
the wider social circles in which they exist. Often, involving
the family in the rehabilitation process can ameliorate the
situation, developing contacts with other visually impaired
people can lessen the anxiety of the person affected by a
visual disorder, and making the wider community cognizant
of the existence of visual impairment can bring about a greater
understanding and acceptance of this ever-increasing reality
in the aging population.
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