Structure of the eyeball
Tear apparatus of the eye
Cross-section of the eyelid
Cross-section of the cornea
Division of the eye
Anterior Segment of the eye
Lens of the eye
Front view of the retina
Cross-section of the retina
Anatomy of the eye
Structure of the eye ball: This is the cross-section(side view) of
the eye. The eye works like the camera, transmitting light and images to
Tear apparatus of the eye: Tears are formed in the Lacrimal Glands
and the Accessory Lacrimal Glands. They are drained via the Lacrimal Ducts,
at the nasal side of the eye, into the Nasolacrimal duct, which opens into
the nose. That is why any eyedrops applied to the eye come into the nose
and throat. Sometimes the Nasolacrimal duct may get blocked and it may then
need to be openned surgically.
Cross-section of the eyelid: The tarsal plate is like a
backbone of the eyelid. It gives strength and flexibility to the
eye lid. The muscles in the lid are attached to this structure.
The Meibomian Glands are like sweat glands. It secretes a fatty
substance which helps in maintaining the surface tension of the
tears. A blockage of these glands leads to a condition called
Cross-section of the Cornea: Cornea is the front
transparent layer of the eye. It is a multi layered structure.
The tears also form a thin layer on top of the cornea and protect
and nourish it. A deficiency of tears can cause Dry eye. Shape of
the Cornea is altered with LASER in Refractive Surgery(Surgery
for correcting spectacle numbers). Any opacity or injury
to this structure can cause permanent opacity and hence loss of
Division of the eye: The eye is divided in two main
parts. The front or Anterior Segment. This has a water like fluid
called Aqueous Humor.The back part or Posterior Segment has a
thick jelly like substance called Vitreous Humor.
Anterior Segment of the eye: It also has 2 sub-sections
divided by the Iris. The Iris is like the shutter of camera. It
controls the amount of light coming in the eye. The Aqueous Humor
enters the chamber from the Ciliary Body and passes through the
hole in the Iris called the Pupil, to exit in the angle between
the Iris and Cornea. Any obstruction in the circulation of this
fluid leads to rise in the eye pressure and can then cause a
condition called Glaucoma.
Lens of the eye: When this becomes opaque, it is called
Cataract. Surgery is the only treatment for Cataract.
Front view of the Retina: Retina is inner layer of the
eye which when stimulated by light sends signal to brain and we
perceive an image. The retina may get detached from the inner
layer and is then put in its place by surgery. Diseases like
Diabetes, High Blood pressure, old age, high myopia, etc can also
damage the retina and can cause permanent loss of vision.
Cross-section of the Retina: Retina is made up of 10
layers. Signal from here are carried by the Optic Nerve to the
brain via the visual pathway. The Optic Nerve can be affected in
many disease, like Glaucoma and Alcohol abuse.
Eye Muscles: They control the eye movement. Any
imbalance in the tone of these muscles can lead to Squint.
Sometimes surgery is necessary to restore the proper balance.
What is Dry Eye?
Dry Eye(also called dry eye syndrome) is a very common condition. Dry eye occurs when people do not have
either enough tears, or the correct composition of tears, on the surface of their eyes to lubricate the eyes and keep them
The diagram shows the tear film and its layers along with the location of the glands responsible for the secretion of
the components of the film onto the surface of the eye. The outer, oily layer of the tear film is produced by the
meibomian glands in the eyelids and reduces evaporation of the tears. The thick, middle, watery layer is made by
the lacrimal gland above the upper eyelid and washes away irritants. The inner, mucus layer is secreted by the
goblet cells in the conjunctiva of the eyelids and helps the tear film stick to the cornea.
The prevalence of Dry Eye increases with age, so that it is extremely common in older people of both sexes. The
condition affects 2 - 3 times more women than men.
If you have dry eye, your eyes can feel persistently gritty, itchy, burning, and painful. These sensations often
worsten as the day goes on. Stringy mucus may appear in or around the eyes. You will know if you have dry eye.
The condition does not require sophisticated diagnosis. Patients with the most severe disease are at increased risk
of developing corneal infection, scarring or ulceration. These conditions can cause permanent vision loss, so it is
important to seek professional help if you have severe symptoms of dry eye.
Dry eye syndrome is not a frequent cause of blindness; however, it is still an important public health problem. One
reason for this is that it is so common. In fact, visits for dry eye syndrome are one of the leading reasons for patients
to seek eye care. This is because its symptoms are very bothersome and lead to a decreased quality of life,
reduced work capacity, and poor psychological health. Furthermore, dry eye syndrome is associated with a
decreased ability to perform activities that require visual attention, such as reading and driving a car.
Severe dry eye is sometimes caused by Sjögren's syndrome, which is a chronic, multi-organ, autoimmune
disorder that also results in dry mouth and often arthritis.You should be under a doctor's frequent care if you
Some very simple tests are used to diagnose dry eye. Schirmmer test is one of them. Here a filter paper strip of a
particular length is kept In the lower lid space and its wetting is measured.
Staining of the Cornea and Conjunctiva with special dye like Fluoroscein and Rose Bengal are some of the other
ways to diagnose dry eye.
Computer Vision Syndrome
People who work on computers or any kind of video display unit for very long hours, tend to develop symptoms of
Some simple measures can help in relieving these symptoms, like working at a comfortable distance from the
monitor, blinking frequently(average of 20 times in a minute), no staring at the monitor, keeping the brightness and
contrast levels of the monitor to a comfortable level, taking intermittent rest during working hours, no sitting in front of
an air draft ( a/c., fan), keeping the monitor at a slightly lower level than the eye, keeping yourself well hydrated,
maintaining a comfortable posture.
Prevention is better than cure
Anything that may cause dryness, such as an overly warm room, hair dryers, smoke or wind should be avoided by
any person with dry eye. A humidifier in heated rooms may help. If wearing contact lenses increases your
discomfort, wear spectacle eye-glasses instead. Some people with dry eye complain of scratchy eyes when they
wake up. This symptom can be treated by using an artificial tear ointment at bedtime. There is some evidence that,
in older women, hormone replacement therapy makes dry eye worse. If you are using HRT, talk to your doctor about
this. And seek help if symptoms occur frequently or interfere with your functioning; it is important to see an
ophthalmolist or optometrist to rule out corneal injury or infection.
The first line of treatment is usually eye drops that act as artificial tears and give some temporary relief. These
solutions and ointments give some temporary relief, but do little to arrest or reverse any damaging conditions. Many
brands are available without a prescription. For mild cases, try several to find the one you like best. The
preservatives in some eye drops can irritate the eye. Preservative-free artificial tears may be required. Researchers
are trying to develop better artificial tears, especially ones that are formulated to normalize the electrolyte balance
while lubricating the ocular surface. One promising new treatment now in clinical trials is the use of eye drops
For more severe cases of dry eye, in which the cornea is inflamed, anti-inflammatory agents are sometimes
prescribed. Topical steroids(in eye drops) are safe for short-term use, to combat inflammation, but can cause
side-effects when used for a long time. A current research area is how to actively suppress inflammatory mechanisms, rather than just
passively lubricate the surface of the eye. Tears drain out of each eye, and into the nose, through a small channel.
Your ophthalmologist may decide to close these channels either temporarily or permanently, to keep the tear film on
the surface for a longer time. For some forms of dry eye, tiny plugs can keep tears on the eye surface by slowing
the rate of drainage from the eye; this procedure is called Punctal Occlusion.
What is Cataract?
Having a cataract is a bit like having a dirty windscreen on a car. It can make the view cloudy or foggy. When the
sun is behind you, the vision through the dirty windscreen is ok, but when you turn into the sun, the view through
the windscreen becomes a white out. A cataract is similar in that glare from lights or the sun when it is low in
the sky and on-coming headlights can all cause problems with the vision. When these problems make normal daily
activities difficult, it is time to get the cataract operated on.
Cataracts do not permanently impair your vision and you will not go blind from a cataract. A simple operation will
restore your sight. Most forms of cataract develop in adult life, and can occur any time after the age of 40. The
normal process of ageing causes the lens to harden and become cloudy. Cataracts can also be caused by injuries
to the eye, for instance, any cuts, blows or burns to the eye that cause damage to the lens inside the eye.
Inside the eye, behind the iris(the colored part of the eye) is a lens. In the normal eye, the lens is clear or
transparent, and helps to focus light rays on to the tissue at the retina at the back of the eye. When a cataract
develops, the lens becomes cloudy and prevents the light rays passing into the retina. The picture that the retina
receives becomes dull and fuzzy. Cataracts usually form slowly and people experience a gradual blurring of vision.
At the clinic, Eye Specialist will check your vision and will take a medical history to find out about your symptoms
and what other medical problems you may or may not have. The doctor will then usually put some dilating drops in
your eyes to make the pupils larger. This enables the eye doctor(ophthalmologist) to have a look at the cataract and
also to look at the retina and the optic nerve and make sure that the cataract and not another problem cause the
The effect of these drops will wear off after a few hours, however, your near vision will be blurred initially. For this
reason you should not drive to appointments and you must be careful that you do not miss your footing, for instance
walking down steps.
Once you have been diagnosed and your cataract progresses to the point that it is interfering with daily activities
and normal lifestyle, you will be given an appointment for an operation to remove the cataract. Surgery is the only
effective way of removing the cloudy lens. It cannot, for instance, be removed by laser, change in diet, or pills. In
some parts of the world it is possible to buy pills to help prevent cataracts, but there is no proof that these work.
If the ophthalmologist thinks your cataract should be removed, you will be advised accordingly. As of today, surgery
is the only treatment for cataracts causing significant visual symptoms. You will be given an appointment shortly
before your operation, when a nurse in the out patients department will carry out special tests to measure your eye.
One of these is a test called Biometry which helps decide the strength of lens that will replace the cloudy
lens in your eye. The nurse will organise any tests for your general health, to make sure you are healthy enough
for surgery, such as blood tests and electrocardiograph(ECG).
If you have cataract developing in both eyes, you will not have treatment to both eyes at the same time. It is
common for cataract to develop more quickly in one eye than the other, and usually, the more seriously affected
eye is operated on first, although the ophthalmologist decides the timing of an operation.
Usually you will be given anesthetics drops or injection outside the eye to make them numb, and you will be awake
throughout the operation. Over 90% of all cataract surgery performed now is done under local anesthetics.
The operation usually takes about half an hour. Your surgeon will remove the cloudy lens by making a tiny opening
into the eye at the edge of the cornea with the help of a machine called as Phacoemulsifier. Through this, he
will remove the cloudy lens and insert a clear plastic implant lens, which will allow you to see again. The surgeon
will use a microscope to perform the procedure.
In 90% of operations done today there is no need to take any stitches. The reason being that in Phacoemulsification
method of cataract surgery the wound is of a very small size(2.5 to 2.8mm only) and this wound closes on its own.
Most operations for cataract are performed on a day care basis. This means that you are admitted to hospital, have
your operation and are discharged home all in the same day. You do not stay overnight in hospital. For a minority
of patients an overnight stay is needed.
After surgery, your operated eye will be covered with a protective plastic eye shield, and you may also have an
eye pad underneath. As the anesthetic wears off, there can sometimes be a dull ache in and around the operated
eye. Ask your doctor for tablets for pain relief.
For day care patients the eye shield(and pad if applied) is removed, the eye lids cleaned and eye examined just
before your return home. If another pad is put on for the first night at home, you will be asked to remove it yourself
the next day and the start to put in your eye drops. All patients are advised to wear the protective plastic eye shield
when in bed at night for a month after the operation.
In preparation for your return home, the nursing staff will show you how to look after your eye, including how to
clean your eyelids and put eye drops properly. Family, friends or colleagues can also be taught how to do this so
that they can help you. The eye drops are necessary because the treatment prevents infection and helps reduce
inflammation after surgery. You will not need to carry on with the drops for more than about two months, however,
please follow the instructions your nurse or doctor give you.
You should avoid rubbing or touching your eye. You may find that you are sensitive to light, so it is useful to have
a pair of plain dark glasses in case you need them.
Patients used to be told not to bend or lift heavy objects for a month, but with todays techniques this advice need
only be taken for a week. After a week all normal activities including work can be resumed. That includes all
The eye takes a few weeks to settle and for vision to return to normal. You will be advised about tests for spectacles
to improve your vision at your next clinic appointment after the operation.
Cataract in children
Babies can be born with cataracts, called Congenital Cataracts. If a child is born with a cataract, surgery is usually
performed as soon as possible to remove it and allow the childs sight to develop naturally.
If the cataract is not removed, eyesight will not develop as the brain does not learn to see pictures properly.
Glaucoma can follow cataract surgery in children, particularly when the cataract surgery has been done very early
in life. The reason for the development of glaucoma after cataract surgery is still not entirely clear. It may be that
very small proteins which are released during cataract surgery block up the flow of the filter system. If the eye
becomes inflamed for any reason, such as in patients who have the childhood form of arthritis, the drainage system
may get blocked with inflammatory cells. As a result, the pressure rises in the eye.
FAQs on Cataract
Q. Do cataracts spread from eye to eye?
A. No. But often they develop in both eyes at the same time.
Q. Has my cataract been caused by overuse of my eyes?
A. No. Cataract is not caused by overuse of the eyes and using the eyes when cataract starts to develop will not
make the cataract worse.
Q. Is it possible not to know you have got a cataract?
A. Some people may or may not be aware that cataract is developing. It can start at the edge of the lens and initially
may not cause problems with vision. Generally, as cataract develops, people experience blurring or hazing of vision.
Often they become more sensitive to light and glare.
Q. As my cataract develops, will I need to get new prescription for my glasses?
A. There may be a need to get new prescriptions for glasses more often when a cataract is developing. When the
cataract worsens, however, stronger glasses no longer improve sight. Objects have to be held close to the eye to
be seen. The hole in the iris(pupil) may no longer look black, a white or yellow appearance may be seen. The lens
behind the pupil becomes more dense and cloudy(opaque) as the cataract develops.
Q. Could anything have been done to stop me developing cataract?
A. There is no known prevention for cataract. Modern surgery is highly successful for the majority of patients.
Q. What are the complications of cataract surgery?
A. Serious complications are uncommon following cataract surgery, however, like all operations problems an
occur occasionally. If any of the following develop you must contact the Eye Surgeon at the earliest.
- Infection or inflammation following cataract surgery is very uncommon but can be serious. If the eye should
become red, sore or aching in the days following surgery, you must contact the eye doctor
- An accumulation of fluid in the retina(Cystoid Macular Edema) can occur, causing blurring of the central
vision. This usually resolves itself within a couple of weeks using drops.
- The implanted lens may occasionally move from its original position causing distorted vision. If this happens,
further surgery may be needed to reposition the displaced lens.
- The retina may become separate from the inner wall of the eye. This is referred to as a retinal detachment and
may require surgery. If you notice sudden shadows in your field of vision, floaters or flashing lights, contact the
- Thickening of the membrane behind the new lens can occur in the months following surgery. This is referred
to as capsular opacity. In this case, although the vision becomes blurred it can be treated with laser.
- In the event that stitches have been used, which is now rare, there is a very small risk of the thread breaking
which makes the eye red and sore.
If you have any concerns following the operation, please see the nearest eye surgeon at the earliest.
Q. Do you use a laser to treat my cataract?
A. Cataracts are treated using a high frequency ultrasound machine. This is the most modern and effective way to
treat cataracts. Although lasers are used in many aspects of eye surgery, they are not used in cataract surgery.
There are some lasers that are being developed to treat cataracts but at present they are not as effective as the ultrasound
Q. Do you have to take my eye out and place it on my cheek in order to operate on it?
What is Glaucoma?
Glaucoma is one of the worlds leading causes of blindess. Glaucoma is not curable, but blindness is preventable if
the glaucoma is diagnosed and treated early enough. While there are usually no warning signs, regular eye tests
will help detect the onset of the disease.
The term Glaucoma covers several different conditions like
- The most common is Chronic(primary open angle) Glaucoma - this form usually affects both eyes and
develops slowly so that loss of sight is gradual. There is no pain, redness of the eye or dramatic change in vision.
- With Acute(angle closure) Glaucoma, there is a sudden increase in the pressure within one eye. The eye
becomes red and painful. Often there is mistiness of vision and episodes of seeing haloes around lights.
- Sometimes, other diseases of the eye cause a rise in the pressure within the eye - this group of conditions is
called Secondary Glaucoma.
- Congenital Glaucoma(buphthalmos) is a condition where glaucoma is present from birth. An increase in the
pressure within the eye causes it to enlarge.
The contents of the eyeball are nourished by a fluid called Aqueous Humour, which is different to tears. It is
secreted within the eye by a tissue called the Ciliary Body, and leaves the eye via another tissue, called the
Trabecular Meshwork. This meshwork is situated at the back of the eye.
An increase in the pressure within the eye usually happens because there is an obstruction within the Trabecular
Meshwork. The obstruction means that the aqueous within the eye is not drawn out, although it continues to be
produced. There is a build up of fluid in the eye, which increases the pressure.
This increased pressure pushes on the back of the eye, which damages the optic nerve. The optic nerve carries
signals to the brain from the eye, and when this is damaged, it causes irrepairablesight loss.
Glaucoma is an eye condition characterized by loss of vision due to damage of the optic nerve. The optic nerve
carries sight images to the brain, and any damage to the nerve results in damage to sight.
Usually, but not always, the damage occurs because pressure within the eye increases and presses on the nerve,
which damages it.
When you come in to see your ophthalmologist, you are likely to undergo some simple, pain free tests. These tests
will allow the doctor to make a diagnosis and help her decide what kind of treatment you will need. You are
advised not to drive to clinic appointments, as some of the eye drops can temporarily blur your vision.
First, the pressure in your eye will need to be measured. An anesthetics drop will be given to numb the front of the
eye. You will be asked to place your head in the slit lamp and the doctor or nurse will shine a blue light into your
eye. The surface of the cornea(window of the eye) will then be touched lightly with an instrument, which measures the eye
You will also need one or more of the following tests:
- Gonioscopy - An anesthetic drop is given to numb the front of the eye. The ophthalmologist holds a special
lens against the cornea. This gives them a better view of the inside of the eye for further examination.
- Visual Field test- The visual field is the range of sight we have on each side of an object we are looking at,
and the extent of the visual field can be measured. The field test takes about 15 minutes per eye. You will be
asked to sit at a screen and keep your gaze fixed on a central light source. You will need to indicate(by pressing
a button) if you can see a series of other lights, no matter how dim, shown during the test. You are not expected
to see all the lights. This test detects if there are any missing areas in your visual field caused by damage to the
- Optic nerve assessment - Drops will be put in your eyes to make your pupils bigger. The effect of these will
wear off after a few hours but may temporarily blur your vision preventing you from reading or driving. The doctor
will then look at the back of the eye through an ophthalmoscope(which looks like a small camera), to check the
health of the optic nerve.
- Photographs - Color photos taken of the back of the eye will be taken and are kept in your file. These can be
used to establish whether any changes occur later. Before photography, drops to make your pupils bigger(as
above) are given.
Your doctor will examine the results of the tests, and will use these to help decide on the best method of treatment
Glaucoma can be treated but not cured. The aim of treatment is to lower the pressure within the eye and prevent
further damage to the optic nerve and visual loss. Because treatment can only control, not cure, the condition, it
must be continued throughout life.
Following types of treatment procedures are available to treat Glaucoma:
- Eye drops
- LASER Surgery
The first form of treatment is usually eye drops, a fluid form of medicine for the eye which lower the eye pressure.
Putting drops in properly and as prescribed is essential to try to prevent any further sight loss.
Drops may sting when first used, and some of the eye drops do have other side effects. Sometimes these arise from
the drops being absorbed too quickly into the blood stream. You can slow the absorption by pressing your forefinger
of your free hand against the lower lid where it meets your nose; or close your eye for 60 seconds.
Pilocarpine drops make your pupil smaller and can temporarily cause brow ache each time the drops are used. In
dim lighting your vision may appear worse. These effects usually wear off after 1 or 2 weeks.
If you notice breathlessness with any eye drops, stop the drops immediately and consult your General Practitioner.
Please inform the clinic doctor if you have a heart or chest condition. Some drops are not suitable for asthmatics.
Tablets of acetazolamide (Diamox®) may be given to patients. These reduce the amount of aqueous produced
within the eye, taking the pressure off the back of the eye.
The tablets initially increase the amount of urine passed and as well as the amount of salts leaving the body. This
can cause some patients to experience tingling in their hands/feet and or nausea and tiredness. If you notice any
side effects tell your ophthalmologist.
In some forms of Glaucoma an operation may be necessary. The most common operation is a Trabeculectomy,
where a small piece of tissue is removed to make a new opening for the aqueous fluid to escape from the eye. The
escaping fluid is absorbed into the tissues which form the outer coat of the eye.
Your doctor will discuss these and any other treatments you are prescribed. It is essential that you follow the course
of treatment given to you as not doing so may result in further loss of sight.
Recently various lasers have been used to manage different types of glaucomas.
Nd:YAG laser is used in Angle Closure type of Glaucoma to make a hole in the Iris, thereby improving the
circulation of Aqueous Humor(watery liquid in the front chamber of the eye). It is also used to make holes in the
Trabecular Meshwork(draining channels in the angle between the cornea and iris), again to facilitate easy drainage
of aqueous, in the Open Angle type of Glaucoma. The procedure is called Selective Laser Trabeculoplasty(SLT).
Both the above procedures are practically painless and are done within a very short time.
Diode Lasers are used in a procedure called Laser Cycloablation, in cases of Glaucoma uncontrolled by other
means, where there is no hope of gaining any form of vision.
FAQs on Glaucoma
Q. Is there any way to prevent glaucoma?
A. No, but regular eye checks will enable early detection and treatment. Please insists on getting your eye pressure
and optic nerve checked every time you have a eye examination.
Q. How did I get glaucoma?
A. Glaucoma is not catching, and is not caused by diet, work or other factors. Many people get Glaucoma as they
get older, and it seems to be part of the natural ageing process. Some groups of people are known to be at more risk:
- Relatives of someone diagnosed with Glaucoma(particularly siblings)
- People of Chinese origin
- People with severe Myopia(short-sightedness)
- People with Diabetes and Uncontrolled high blood pressure.
Q. Will I go blind from glaucoma?
A. If you have been diagnosed with Glaucoma, this does not mean you will go blind, especially if you have been
diagnosed with Glaucoma at an early stage in the disease. Drops and sometimes operations can stabilize the
Glaucoma, and with regular check-ups, you will be able to manage the condition. You will experience some degree
of sight loss but it will be minimized with effective treatment.
Diabetic Macular Edema
Severe Nonproliferative Diabetic Retinopathy
Diabetic Eye Disease
Diabetes is a chronic(lifelong) disease in which carbohydrate(Glucose ) metabolism(breakdown ) is abnormal due to
insufficient level of Insulin hormone in the body. High glucose blood level is the hallmark of this disease. This
causes many secondary effects on all organs and systems in the body.
Diabetic eye disease is one of the vital and potentially dangerous complication 0f diabetes. If it remains undetected
and therefore untreated it can cause permanent blindness.
What is Diabetic Eye?
Diabetic eye disease refers to a group of eye problems that people with diabetes may face as a complication of this
disease. All can cause severe vision loss or even blindness.
Diabetic eye disease may include:
- Diabetic retinopathy - damage to the blood vessels in the retina.
- Cataract - clouding of the eye lens.
- Glaucoma - increase in fluid pressure inside the eye that leads to optic nerve damage and loss of vision
Most common Diabetic Eye disease
Diabetic retinopathy. This disease is a leading cause of blindness all over the world. It is caused by changes in the
blood vessels of the retina. In some people with diabetic retinopathy, retinal blood vessels may swell and leak fluid.
In other people, abnormal new blood vessels grow on the surface of the retina. These changes may result in vision
loss or blindness.
Often there are none in the early stages of the disease. Vision may not change until the disease becomes severe.
Nor is there any pain. Blurred vision may occur when the macula - the part of the retina that provides sharp, central
vision - swells from the leaking fluid. This condition is called macular edema. If new vessels have grown on the
surface of the retina, they can bleed into the eye, blocking vision. But, even in more advanced cases, the disease
may progress a long way without symptoms. That is why regular eye examinations for people with diabetes are so
Most likely to be affected
Anyone with diabetes. The longer someone has diabetes, the more likely he/she will get diabetic retinopathy.
Between 40-45 percent of those with diagnosed diabetes have some degree of diabetic retinopathy.
If you have diabetes, you should have your eyes examined at least once a year. Your eyes should be dilated
during the exam. That means eyedrops are used to enlarge your pupils. This allows the eye care professional to see
more of the inside of your eyes to check for signs of the disease. In some patients special procedures are done to
detect changes which could lead to blindness. These are Fundus Photography, Fundus Fluoroscein
Angiography(FFA) and Optical Coherence Tomography(OCT). The figure is that of a normal Fundus Angiogram.
Your eye care professional may suggest laser surgery in which a strong light beam is aimed onto the retina. Laser
surgery and appropriate follow-up care can reduce the risk of blindness by 90 percent. However, laser surgery
often cannot restore vision that has already been lost. That is why finding diabetic retinopathy early is the best way
to prevent vision loss.
In patients with very advanced diabetic eye disease, surgery is necessary to remove the accumulated blood and
clear the scar tissue from inside the eye(Vitrectomy).
Diabetic Retinopathy cannot be totally prevented, but your risk can be greatly reduced. The Diabetes Control and
Complications Trial (DCCT) showed that better control of blood sugar level slows the onset and progression of
retinopathy and lessens the need for laser surgery for severe retinopathy.
The study found that the group that tried to keep their blood sugar levels as close to normal as possible also had
much less kidney and nerve disease. This level of blood sugar control may not be best for everyone, including
some elderly patients, children under 13, or people with heart disease. So ask your doctor if this program is right for
Other Diabetic Eye Diseases
If you have diabetes, you are also at risk for other diabetic eye diseases. Cataracts develop at an earlier age in
people with diabetes. Cataracts can usually be treated by surgery.
Glaucoma may also become a problem. A person with diabetes is nearly twice as likely to get glaucoma as other
adults. And, as with diabetic retinopathy, the longer you have had diabetes, the greater your risk of getting
glaucoma. Glaucoma may be treated with medications, laser, or other forms of surgery.
Much research is being done to learn more about diabetic eye disease. This research should provide better ways to
detect and treat diabetic eye disease and prevent blindness in more people with diabetes.
Protection of vision
Finding and treating the disease early, before it causes vision loss or blindness, is the best way to control diabetic
eye disease. So, if you have diabetes, make sure you get a dilated eye examination at least once a year.
In a nutshell
Diabetes is a disease that can cause very serious health problems. If you have diabetes:
- Know your ABCs-A1C (blood glucose), blood pressure (BP), and cholesterol numbers.
- Take your medicines as prescribed by your doctor.
- Monitor your blood sugar daily.
- Reach and stay at a healthy weight.
- Get regular physical activity.
- Quit smoking.
Squint is the term used when the eyes are not exactly straight. When looking at an object, normal eyes will look
exactly in the same direction. This is required for the light to fall on exactly the same parts of the two retinas(the
backs of the eyes). If a squint is present the two eyes cannot focus on exactly the same point.
The severity can vary. Some squints are very marked and obvious. Some only become noticeable when the child is
tired. Some are quite small and are only discovered by a proper examination.
The cause can vary. Sometimes they are due to muscle or nerve problems of the eye. Sometimes eye diseases
cause a squint. However, the majority are due to one eye being more longsighted than the other. In this common
situation one eye has to strain more than the other to see clearly and this can lead to a squint.
The direction can vary. Most are convergent i.e. the squinting eye tends to look inwards. However, the squinting
eye can be divergent(looking outward) or looking up or down.
Broadly Squint is divided in 2 types:
- Incommitant(where the degree of squint varies in different directions)
- Commitent(where the squint in all directions of gaze remains the same)
The Incommitent squint is mainly due to paralysis of one or muscles of the eye.
The Commitent type has multiple reasons. It is broadly classified as
- Exotropia(eyes move out)
- Esotropia(Eyes move inwards)
- Vertical squints(misalignment of eyes in vertical direction)
Exotropia is the outward deviation(turn) of an eye. The deviation may occur while fixating(looking at) distant objects,
near objects or both. Fortunately, most exotropia is intermittent and this means that the eye deviation or turn occurs
only some of the time. As long as the eyes are straight some of the time, the brain will develop some normal
functioning of the eyes(stereoscopic depth perception). Since the brain and eyes work properly some of the time,
time is on your side.
Treatment for intermittent exotropia does not have to occur immediately. As a matter of fact, early surgery has the
potential of disturbing the ability of the brain for fusion in the future and can cause a permanent reduction in vision
When the turn occurs during distance viewing the major problem is cosmetic. The child might be accused of
daydreaming or not paying attention. The parents will often notice the turn and then they bring their child to the eye
doctor who might not find it. This is because the turn usually occurs during times of inattention, fatigue, or distance
viewing not during the anxiety-provoking eye examination. These children often close their eye in bright sunlight.
If the squint is constant and is causing disruption of the ability of stereopsis(three dimensional vision) then corrective
muscle surgery is the only tretment.
Esotropia can be divided into various categories each requiring a different treatment plan, each having a different
Types of Esotropia
There are following 4 types of Esotropia:
- Congenital Esotropia
- Infantile Esotropia
- Accommodative Esotropia
- Partially Accommodative Esotropia
Congenital and Infantile Esotropia
Congenital means from birth and, using this strict definition, most infants are born with eyes that are not
aligned at birth. Only 23% of infants are born with straight eyes. In the majority of cases, one eye or the other
actually turns outward during the neonatal period. Within the first three months the eyes gradually come into more
consistent alignment as coordination of the two eyes together as a team develops.
It is common for infants to appear as if they have Esotropia, or inward turn of the eyes, because the bridge of the
nose is not fully developed. This false or simulated appearance of an inward turning is known as Epicanthus. As the
infant grows, and the bridge narrows so that more of the white of the eyes(Sclera) is visible on the inner side, the
eyes will appear more normal.
True Congenital Esotropia is an inward turn of a large amount, and is present in very few children, but the infant will
not grow out of this turn. True Infantile Esotropia usually appears between the ages of 2 and 4 months.
The baby with Infantile Esotropia usually cross fixates, which means that he or she uses either eye to look in the
opposite direction. The right eye is used to look toward the left side, and the left eye is used to look toward the right
side. By definition, they alternate which eye they are looking with. It is more difficult to help this type of Strabismus
with non-surgical methods, such as vision therapy and/or glasses. Sometimes, clear tape applied to the inner third
of each lens(Occlusion) can reduce the tendency to turn inward. Prisms may aid alignment if the turn is not too large.
Some children who develop Strabismus, in which coordination between the two eyes is poor, also have a typical
gross motor development patterns. They typically skip the crawling stage with bilateral movements, and go right from
creeping to standing. The interplay between gross motor, particularly balance systems(Cerebellar and Vestibular)
and Binocular Systems(motor control of the two eyes) is evident in the large number of young children with Cerebral
Palsy who have Strabismus.
If the inward turn of the eye is constant, and of a large amount, surgery may be indicated. Both the parent and
surgeon have to be committed to multiple procedures to obtain perfect alignment. Improved alignment may look
better cosmetically, but it does not necessarily enable the brain to utilize information from both eyes together.
Stereopsis, or two-eyed depth perception, is often poor following surgical treatment. The best chance for visual
success occurs when the surgeon works with an Optometrist who is comfortable in prescribing glasses and
exercises to encourage perfect alignment of the eyes with proper fusion. This model of cooperative care is similar to
the relationship between the orthopedic surgeon and physical therapist.
If Amblyopia is present(poorer vision in the turned eye), therapy including patching is often required so that the
turned eye develops the capacity to see as well as the better eye. It is best to do this before surgery.
The chance of developing Binocular Vision with surgery alone diminishes with age. Older children with Infantile
Esotropia may need both surgical intervention and vision therapy. Smaller turns may only require vision therapy.
Getting the eyes to work together requires a lot of time and effort, but is usually worth it.
If excessive inward turning of an eye is first noted around 2 years of age, it may be due to difficulty integrating the
focusing(accommodative) system with the eye alignment(binocular) system. Normally when we look across the room
or beyond, our eyes are parallel, or straight. However, when we look at things up close, two things happen. We
need to converge more(aim both eyes inward at the same time) and we have to input more focus, or accommodate
to keep things clear. Children have large amounts of focusing power, and sometimes in getting things clear, inward
turning or Esotropia results. If the inward turning only occurs up close, as when playing with small objects, making
eye contact, coloring, looking at picture books and so forth, the child may just need glasses for near activities to
reduce or eliminate the esotropia.
However, if a child is significantly farsighted(Hyperopia), an inward turn of the eye may even occur when focusing
to look further away, such as television. If the amount of turn is greater at near than far, your optometrist may
prescribe a multifocal lens. For children this could be a traditional bifocal with a line, or a form of no-line bifocal or
progressive lens. Your optometrist will review with you which is the best option for your child. In addition, vision
therapy may be of benefit. This condition should never be treated with surgery.
When the eyes are aligned by corrective lenses sometimes the eyes spontaneously begin to work together. Other
times, they need help. Remember, the habit of suppressing or turning off one eye or the other was probably
developed over a number of years. The eyes have to be trained to work together again and suppression must be
eliminated in order to restore normal eye teaming, depth perception, and stereopsis. The eye doctor might have to
patch an eye that was suppressed or turned off and/or employ vision therapy.
Intermittent turns usually do not require long term treatment. Vision Therapy may be necessary to improve the
muscle coordination and eventually eliminate the bifocal.
Patients with Accommodative Esotropia should never have eye muscle surgery to eliminate the need for glasses. If
they do, they will have significant focusing problems when they get older. In the future, these patients might be
excellent candidates for refractive surgery(Hyperopic LASIX) or contact lenses. This should be coordinated with the
developmental Optometrist and LASIK surgeon.
Partially Accommodative Esotropia
In some instances, part of the inward turn is due to basic Esotropia, and an additional amount due to the effect of
accommodation. Glasses may reduce the amount of eye turn, but it is not totally compensated. Initially, the eye
doctor may prescribe prism to compensate for the amount of turn. Office-based Vision Therapy is usually needed.
Surgery remains an option to address the non-accommodative portion of the Esotropia. Remember that surgery
alone rarely enables a patient to learn how to use both eyes together as a team, and usually leaves the patient with
poor Stereopsis. Because vision is a learned process, some form of therapy is often helpful in learning new
binocular vision patterns, or restoring normal pathways that have been lost or underutilized. Binocular vision occurs
in the visual centers of the brain, not in the eye muscles.
Upward deviation of the eye is usually due to a paresis of one of the muscles that either elevate or depress the eye.
Most of the time it is due to one specific muscle known as the Superior Oblique. The paresis may be
congenital(born with it) or acquired. Most of the time, palsy of the superior oblique is congenital but may present
itself later in life. For one reason or another the fusion system breaks down and the deviation becomes manifest. An
inexperienced doctor may send this patient out for extensive neurological testing including MRI. There are tell tale
signs that tell the sophisticated doctor that the turn has been there a long time and one does not have to worry
about it such as a head tilt being present in old pictures, etc.
If the Hypertropia is a decompensation of a congenital deviation, then treatment may consist of prism glasses and
vision therapy. Our goal is fusion without prismatic glasses. However, often, treatment requires small amount of prism
to hold the eyes in comfortable alignment.
Amblyopia causes more visual loss in the under 40 group than all the injuries and diseases combined in this age
group. If not detected and treated early in life, amblyopia can cause loss of vision and depth perception. Improvements are possible at
any age with proper treatment, but early detection and treatment offer the best outcome. Comprehensive vision
screenings are needed for infants and pre-school children. An eye exam by a pediatrician or the 20/20 eye chart screening is not
adequate for the detection of amblyopia (and other visual conditions).
Amblyopia, commonly known as lazy eye, is the eye condition noted by reduced vision not correctable by glasses
or contact lenses and is not due to any eye disease. The brain, for some reason, does not fully acknowledge the
images seen by the amblyopic eye. This almost always affects only one eye but may manifest with reduction of
vision in both eyes. It is estimated that 3% of children under six have some form of amblyopia.
Causes of Lazy Eye
Anything that interferes with clear vision in either eye during the critical period(birth to 6 years of age) can cause
amblyopia. The most common causes of amblyopia are constant strabismus(constant turn of one eye),
anisometropia(different vision/prescriptions in each eye), and/or blockage of an eye due to cataract, trauma, lid
Amblyopia is a neurologically active process. In other words, the loss of vision takes place in the brain. If one eye
sees clearly and the other sees a blur, the brain can inhibit(block, ignore, suppress) the eye with the blur. The brain
can also suppress one eye to avoid double vision. The inhibition process(suppression) can result in a permanent
decrease in the vision in the blurry eye that can not be corrected with glasses, lenses, or lasik surgery.
Detection and diagnosis of Lazy Eye
An eye exam by a pediatrician or the 20/20 eye chart screening is not adequate for the detection of
amblyopia(and other visual conditions). The most important diagnostic tools are the special visual acuity tests other
than the 20/20 letter charts currently used by schools, pediatricians and eye doctors. Examination with cycloplegic
drops can be necessary to detect this condition in the young.
Since amblyopia usually occurs in one eye only, many parents and children are unaware of the condition. Many
children go undiagnosed until they have their eyes examined at the eye doctor's office at a later age.
Comprehensive vision evaluations are highly recommended for infants and pre-school children.
Treatment of Lazy Eye
- Early detection of factors causing amblyopia is most effective means of treating Amblyopia.
- Screening of child before he/she starts school by an ophthalmologist is absolutely a must.
- If the child has refractive errors in any of his/her eyes, then it has to be worn from a very early age.
- Special exercises with one eye patched for a specified period of time is the most & only effective treatment for improving a amblyopic childs eyesight.
If the squint is large it can be a cosmetic problem when the child grows up. However, another important
complication is amblyopia. This means that vision can be gradually affected if the squinting eye is left untreated. As
mentioned above, even in very minor squints, if the two eyes are not exactly straight they cannot focus on the same
point. This confuses the brain as two images are seen at the same time causing double vision. The weaker
image then tends to be ignored by the brain. This weaker eye then gradually loses its power(just like if you
never use one arm it will become wasted and weak). This loss in vision takes years to develop but is irreversible.
Therefore even very slight squints in children should be treated.
The aim of the treatment is to get the weaker squinting eye trained up. If the cause of the squint is due
to one eye being more long-sighted then wearing glasses to correct this may do the trick. Sometimes wearing a
patch on the good eye to train up the weaker eye is advised for part of each day. Eye muscle exercises are
sometimes tried. If the squint is large and the above measures do not seem to be helping, then an operation is
sometimes performed to correct the squint. Treatments are usually under the supervision of Orthoptists who are
specially trained people who deal with all aspects of squint and work in close co-operation with eye surgeons.
What is Refractive Error?
By definition a refractive error is an abnormality of the eye where the light rays do not converge on the Retina. Due
to this a person has blurred image of objects and hence a subnormal eyesight.
There are three main types of Refractive Errors
In Hypermetropia the image forms behind the retina. Hence if the object is beyond a particular distance, it is visible
little more clearly, than if the object is near the eye. A person who crosses the age of 40yrs needs glasses,
particularly for reading and near work. This is called Presb.
Another variety of hypermetropia is called Presbyopia. A person who crosses the age of 40yrs needs glasses,
particularly for reading and near work. This is called Presbyopic error. This is because after this age the muscles
controlling the ability to focus for near start becoming weak.
Children who have this kind of error need to diagnosed very early, otherwise they can loose there eyesight and this
can have an effect on there school performance.
Three options are available to treat hypermetropia
- Contact lenses
- Refractive surgery
Refractive surgery is done in various ways. Lasik involves surgery on the Cornea. Similarly Conductive
Keratoplasty is a new technique to treat Presbyopic type of refractive error. It is still not very popular, but will be in vogue in
future. Prelex is a combination surgery involving surgery on the cornea and implantation of special type of lenses
inside the eye.
In Myopia the light rays fall in front of the retina. Hence a person with this defect will have better near vision than for
distance. Generally the cause of this error is an abnormally long eyeball, but this error could also be due to abnormal shape of
cornea. Heredity is one of the strong factors for myopia.
A person who develops myopia late in life is due to cataracts and this is temporary. A person who has myopia of
high degree, has a chance of developing break in the retina, which can lead to loss of eyesight. Hence such
persons are advised to undergo a very simple screening test of the retina, and if any such defects are noticed the
they need to be treated at the earliest(by laser).
Three options are available to treat myopia
- Contact lenses
- Refractive surgery
Two types of Refractive surgeries are done for treating Myopia. Lasik is the commonest refractive surgery done
anywhere in the world. A corneal flap of a particular thickness is taken(slice of cornea). This flap remains attached
to the cornea at one end. Laser is then done on the exposed bed of the cornea and the flap is repositioned back.
Phakic lens implantation is one more option for person with very high myopia (more than - 10). A specially designed
lens is implanted inside the eye, without removing the original lens.
In Astigmatism, some part of light rays fall on the retina, while some part do not. Hence the image seen by persons
with this kind of error is abnormal in shape or elongated. Astigmatism can of the Hypermetropic or Myopic type or
sometimes it could be a combination of both.
Three options are available to treat Astigmatism
- Glasses(Cylindrical lenses)
- Contact lenses(Toric)
- Refractive surgery
Contact lenses are worn on the cornea as an alternative to glasses. The main advantage of contact lenses is that it
eliminates any artificially induced restriction in vision due to spectacle. Contact lenses ,therefore give near natural
vision to a person having refractive errors. It also adds to the personality of a person.
Contact lenses are of two types
The Hard/Semisoft type of contact lenses are the older variety of lenses. The only advantage of this type of lens is,
that they are durable and long lasting. However they are uncomfortable to wear and often not easily tolerated.
Soft Contact lenses are the most preferred type of lenses. They are more comfortable to wear and more suitable to
There are 4 types of soft lenses
- Soft lenses for spherical type of numbers:- Here lenses are of the yearly duration, quarterly duration or monthly use
- Toric soft lenses:- These are lenses used by persons having astigmatism(Cylindrical power)
- Multifocal lenses:- These lenses are used by people who need glasses for reading and distance both
- Coloured lenses:= Lenses of various colors are available for cosmetic purpose
Care to be taken while using soft contact lenses
While learning to use soft lenses for the first time, always do all movements very slowly. Do not rush into learning to
wear or remove lense from the eye. Sometimes it can lead to injury to the eye if proper instructions from the doctor
are not followed. Always wash hands and dry them before wearing and removing lenses. Do not wash soft lenses
with water. Use the contact lens cleaning solution only to clean the lens. Do not sleep with the lens in the eye.
Change the contact lens solution every 2-3 days. Keep the contact lens container clean. Do not use any kind of
cosmetics or eye drops when wearing the lens.