Every five seconds an adult goes blind somewhere in the world,
and every 60 seconds a child goes blind.
Using the World
Health Organization (WHO) definition of blindness, defined as
vision in the better eye of less than 3/60, it is estimated that
there are about 45 million blind people in the world.
There are
also about 135 million people who are visually impaired and
who need help.
Leading causes of blindness
worldwide
Ninety per cent of the world’s blind and visually impaired
people live in the countries of the developing world.
The
impact of medical progress has been greatest in the more
affluent countries of the developed world, where economic
resources have facilitated significant advances in tackling
blinding diseases.
Two hundred years ago the main cause of blindness in
western Europe was smallpox; 100 years ago this was replaced
by ophthalmia neonatorum.
Although there are success stories
in the battle against blindness, it is important to remember that
blinding diseases still represent one of the major problems
facing developing nations.
Causes of blindness in the developing world
Cataract
About 20 million people are blind in both eyes because
of cataracts.
These people could all be treated if they
had access to cataract surgery, and currently there are
large scale programmes under way in many developing
countries.
Glaucoma
If glaucoma is detected at an early stage then blindness is
usually avoidable.
However, long term topical glaucoma therapy
is not practicable in many low income countries, because of
cost, compliance, and access issues.
Currently several research
programmes are evaluating the feasibility of surgery.
In areas of the world where angle closure glaucoma has a high prevalence,
laser therapy (peripheral iridotomy) has the potential to
prevent much blinding disease.
Trachoma
Infection with Chlamydia trachomatis causes this severe scarring
conjunctival infection.
Basic hygiene and public health
measures can dramatically reduce the prevalence of blinding
infection.
Vitamin A deficiency
Vitamin A is needed to maintain epithelial surfaces (including
the ocular surface) and to make retinal photoreceptor
pigments.
Deficiency of vitamin A (xerophthalmia) causes
ocular surface dryness, scarring, infection with possible
perforation, and night blindness.
Vitamin A supplementation
can eradicate this important blinding disease, which, coupled
with common childhood infections (such as measles), is a
major cause of blindness in children.
Onchocerciasis
“River blindness” is caused by the parasite
Onchocerca volvulus,
carried by the blackfly, which transfers the parasite when it bites
humans. Infection results in corneal scarring, cataract,
glaucoma, and chorioretinitis.
Treatment with ivermectin can
help control parasite levels in infected individuals, and public
health measures to eradicate the blackfly vector, which breeds
in fast flowing rivers, can reduce disease prevalence.
Changing nature of blindness
in “middle income” countries
Many South American and eastern European countries now fall
into this economic category.
The extreme poverty common in
the developing world is not so prevalent in these countries, and
there are pockets of very high quality ophthalmic care.
Two
ophthalmic diseases in particular have the potential to increase
dramatically in prevalence in “middle income” countries:
retinopathy of prematurity and diabetic retinopathy.
Retinopathy of prematurity (ROP)
The prevalence of blinding ROP is increasing in many “middle
income” countries because basic neonatal intensive care
facilities are available.
Although better neonatal care means
more babies survive, there are usually very limited facilities for
monitoring babies.
As a result, many babies receive
unmonitored supplemental oxygen therapy and therefore are
at increased risk of developing severe ROP.
Diabetic retinopathy
As the levels of income, nutrition, and basic health care
increase, more patients with type 1 and type 2 diabetes will
survive into later life.
Many of these patients will develop sight
threatening diabetic retinopathy, but there is simply not
enough access to laser treatment facilities to manage their
retinopathy and prevent blinding complications.
Eye disease in patients from outside
the United Kingdom
With modern air travel, the number of people travelling to the
United Kingdom from developing countries has increased
dramatically.
An overseas patient with an ophthalmic problem
may have a tropical ophthalmic disease not usually seen in
the United Kingdom (for example, red eye due to trachoma)
or an ophthalmic manifestation of a systemic disease (for
example, red eye and uveitis secondary to tuberculosis).
Travelling outside the United Kingdom
Many patients will ask their family doctor for ophthalmic advice
before travelling.
Some common questions are answered below.
Can I fly after surgery for retinal detachment?
Patients who have had gas injected inside their eyes to provide
tamponade as part of surgery for retinal detachment should
consult their ophthalmic surgeon before flying, as it usually
takes several weeks for the potentially expansile gas (sulphur
hexafluoride) to be absorbed postoperatively.
Aircraft cabins
are usually pressurised (to about 8000 feet) during flight, which
can cause the intraocular gas to expand while the plane is in
the air, leading to acute glaucoma.
How soon after eye surgery can I go abroad?
All patients who have had intraocular surgery (for example,
cataract surgery) are at risk of delayed complications such as
inflammation or infection for the first two to four weeks post
operatively.
The patient should consult their ophthalmic
surgeon before arranging travel abroad.
Should I take any precautions because of my
eye problems?
● Patients who are prone to recurrent uveitis or corneal herpetic
disease may experience a reactivation of their problem while
abroad.
Patients should carry basic information about their
condition with them and may carry a supply of appropriate
medication in case of a flare up.
It is always best to seek an
expert ophthalmic opinion before starting therapy abroad
● Patients who have had previous glaucoma surgery may
benefit from carrying a supply of topical antibiotics in case
they develop an infective conjunctivitis
● Individuals that wear contact lenses should pay strict
attention to hygiene when using lenses in developing
countries. Non-sterile water (for example, from taps) used to
clean contact lenses or contact lens cases may be a source of
pathogens such as acanthamoeba, which can cause
intractable, potentially blinding infection.
Care should be
taken with contact lens hygiene, especially if wearing contact
lenses on long haul flights.
Daily wear contact lenses should
not be worn overnight on long flights, because the cabin
partial pressure of oxygen is reduced considerably
● Patients with “dry eye” syndromes may experience a marked
exacerbation of their symptoms in the dry atmosphere of the
aircraft cabin and should carry a supply of ocular lubricants.
