abnormalities may be divided into two categories
- abnormalities of lens size and shape, which are
largely developmental, and abnormalities of lens
clarity, or cataract.
A cataract is essentially an abnormality in
lens clarity, which can lead to impaired vision
even absolute blindness. It is one of the most
common ailments affecting people (particularly
aged people) worldwide. There are several factors
contributing to the cause apart from age such
as exposure to ultraviolet light, smoking and
alcohol, genetic composition, and diabetes.
Studies on the biochemistry and normal physiology
the lens and the changes that induce cataract
An effective method, which could restrain the
formation of a cataractous lens, has yet to be
developed. However, normal visual function can
by cataract surgery which involves applying an
artificial intraocular lens.
Developed countries throughout the world
allot a significant portion of their health care
budgets for cataract surgery. The United States
makes a huge annual expenditure on cataract-related
services. The scenario in the developing world
is quite miserable – the numbers of new
cataract cases significantly outnumber the rate
of surgical removal. In Africa, not even half
of cataracts each year have their sight restored
Cataracts can be defined as an eye disease in
which the crystalline lens or its capsule becomes
Its effect on the vision may be incontrovertible
or convertible. It eventually results in loss
There are various causes of cataract development,
which include metabolic disorders, developmental
abnormalities, trauma and drug-induced changes.
The major cause of visually evidential cataracts
is ageing. As we grow old the lenses in our eyes
deteriorate. For some, cataract development occurs.
Classification of Cataracts
The cause of age related changes in the lens
due to cataracts has not been explored fully
but it is expected to be multifactorial. There
main classifications of age-related cataracts
defined according to their clinical appearance:
cortical, nuclear, and posterior subcapsular.
With cortical cataracts new lens fibers are
formed on the cortex of the lens. These fibers
ageing and new fibers continue to grow forming
a layer on outer portion of the lens, under the
outer coating or capsule of the lens. Ageing
causes discrete opacities (cortical spokes) within
the cortex of the lens. There are no visual problems
until they affect the visual axis or the entire
cortex, as the lens becomes white and matures.
The nucleus of a lens is compressed with aging
and becomes harder (nuclear sclerosis cataract).
of cataract is associated with yellowing of the
lens. This progresses gradually over the years.
It certain cases the affected person experiences
a change in refraction (myopic shift) which is
often referred as second sight, as he/she does
not usually require glasses for reading. However,
progression there can be a loss of vision, especially
for near vision.
Occurrence of granular opacities primarily in
the central posterior cortex causes this type
of cataract. It is generally more common in younger
patients. Affected patients suffer symptoms
such as complaint of glare when driving at night
near vision acuity more than distant vision.
Factors responsible for cataracts
The epidemiological studies suggest a number
of risk factors are associated with cataracts:
- One of the major factors is increasing
age, which is often responsible for nuclear
and cortical opacities.
- Ethnic variation
can be associated with different
types of cataracts and variable rates of prevalence.
- Genetic factors are held responsible for
nearly half of the severity of nuclear cataracts
and are considered important in development
of cortical cataracts. The studies show that
recessive genes are potential inciters of cortical
and nuclear cataract development.
- According to the evidence,
women have a greater chance of developing cataracts
- External factors responsible
for Cataractogenesis (development of cataracts)
are sunlight, cigarette smoking, alcohol consumption,
lack of nutritional supplements, and lower
education. Further, the studies reveal that
light sources such as ultraviolet B (UV-B) rays produce
lens opacities in the human eye leading to
cortical cataract development. These factors
are also related with
certain health problems.
- Common medical
factors such as diarrhea, dehydration, diabetes,
use of steroids, and use of certain systemic
medications, increases the risk of cataracts.
to be largely associated with development of
cortical and posterior subcapsular cataracts,
subjecte to the duration of the disease and
degree of successful diabetes control. The
studies have found that diabetics suffer
lens opacities or require cataract surgery
than nondiabetics. Moreover, diabetes seems to be
associated with early-age cataract development.
- Poor nutrition
is also an indicator of higher cataract risk,
especially deficiency of antioxidant
vitamins A, C, and E are significant.
The diagnosis of cataracts is done through estimation
of visual function, which requires the measurement
of visual acuity with the help of a vision chart.
The vision chart consists of black letters on
a white background, which the patient has to
read in a darkened room from a distance and with
lights on for near vision.
For proper detection of ocular diseases, like
dry eyes or abnormal cornea, it is necessary
to have an ophthalmic eye examination, as these
could impede a successful cataract surgery. It
also help to avoid other causes diabetic retinopathy,
macular degeneration, or glaucoma. The examinations
include measurement of vision using a slit-lamp,
testing intraocular pressure, and dilation of
pupils for thorough examination of the lens,
vitreous inside the eye.
Sophisticated surgical techniques have made
removal of cataracts easier than ever. The use
of viscoelastics, phacoemulsifcation and the
development of intraocular lenses, have made
treatment quite effective and ensures steady
visual recovery in most cases.
Cataract surgery essentially depends on the
visual needs. There are a few cases of ocular
disease, such as diabetic retinopathy, that
not justify cataract surgery. The patient needs
to be informed on other options such as use of
aids, and of the effect of surgical intervention
before a decision on whether or not to have surgery
can be made.
TMethods of delaying
be discovered. Currently there are no proven
ways to stop cataracts from developing other
than maintaining a healthy lifestyle and cutting
out the apparent risk factors such as smoking
and nutrient deficient diets.
Cataract surgeries have a high rate of success,
but no procedure is without risk. So, before
deciding on cataract surgery, the risks, benefits,
and patient’s expectations should be evaluated
by the doctor. The patient too must decide whether
the benefits of surgery outweigh the risks.