Knowledge
Pub
Know the Diseases :
The main
eye related problems are :
1.
Cataract
2. Glaucoma
3. Diabetic Retinopathy
4. Retinal Detachment
5. Lasik
Cataract
Click
here for video clip of cataract operation with foldable lens (Phacoemulsification)
---Need real player download here---
Human
Eye:
The basic structure of the human eye is like a Camera. In a normal eye,
light rayspass through the "Cornea" & "Lens" and
get focused exactly on the "Retina". In our eyes, the "lens"
is the important part of the eye that helps to focus light on the "Retina".
The retina is the eye's light-sensitive layer that sends visual signals
to the brain via Optical Nerve. So to produce a sharp image, the lens
must remain clear.
Cataract :
The Lens, which is responsible for focusing light and producing sharp
images, is a clear tissue located behind the pupil - the dark circular
opening in the middle of the iris or colored part of the eye. The lens
works with the transparent cornea, which covers the eye's surface, to
focus light on the retina at the back of the eye. When the lens becomes
cloudy, light cannot reach to the retina properly, and vision is blurred
and decreased. This can start to cloud small areas of the lens, blocking
some light from reaching the retina and interfering with vision. This
is called a Cataract. So cataract is formed when the natural lens of the
eye becomes cloudy and hardens, resulting in a loss of visual function.
Causes
of Cataract:
Everyone is at risk of developing cataracts simply because age is the
single greatest risk factor.
*Diabetes
*Family history of cataracts
*Previous eye injury or inflammation
*Previous eye surgery
*Prolonged use of corticosteroids
*Excessive consumption of alcohol
*Excessive exposure to sunlight
*Exposure to high levels of radiation, such as from cancer therapy
*Smoking
Types of Cataract :-
*Age-related cataract: Most cataracts are related to aging.
*Congenital cataract: Some babies are born with cataracts or develop them
in childhood, often in both eyes. These cataracts may not affect vision.
If they do, they may need to be removed.
*Secondary cataract: Cataracts are more likely to develop in people who
have certain other health problems, such as diabetes. Also, cataracts
are sometimes linked to long term steroid use.
*Traumatic cataract: Cataracts can develop soon after an eye injury, or
years later.
Symptoms: Here are some signs of a cataract:
*Cloudy, fuzzy, foggy, or filmy vision.
*Changes in the way you see colors.
*Problems while driving at night because headlights seem too bright.
*Problems with glare from lamps or the sun.
*Frequent changes in your eyeglass prescription.
*Double vision.
*Better near vision for a while only in farsighted people.
How to Diagnose a Cataract ?
To detect a cataract, an eye care professional examines the lens. A comprehensive
eye examination usually includes:
*Visual acuity test. Acuity refers to the sharpness of your vision or
how clearly you see an object. In this test, your eye doctor checks to
see how well you read letters from across the room. Your eyes are tested
one at a time, while the other eye is covered. Using the chart with progressively
smaller letters from top to bottom (the standard Snellen chart), your
eye doctor determines if you have 20/20 or 6/6 vision or less acute vision.
*Slit-lamp examination. A slit lamp allows your eye doctor to see the
structures at the front of your eye under magnification. The microscope
is called a slit lamp because it uses an intense line of light - a slit
- to provide oblique illumination of the cornea, the iris, the lens and
the space between the iris and cornea. The slit allows your doctor to
view these structures in cross section and detect any small abnormalities.
*Retinal examination. In this procedure, your eye doctor puts dilating
drops in your eyes to open your pupils wide and provide a bigger window
to the back of your eye. Using a slit lamp or ophthalmoscope, he or she
can examine your lens for signs of a cataract and, if needed, determine
how dense the clouding is. He or she will also check for glaucoma and,
if you have blurred vision or discomfort, for other problems involving
the retina and the optic nerve. Dilating drops usually keep your pupils
open for a few hours before their effect gradually wears off. Until then,
you probably will have difficulty focusing on close objects, but your
distance vision shouldn't be affected. With your pupils open this wide,
you'll probably need sunglasses for your trip home, especially if it's
a bright day. It would be safer to let someone else do the driving, after
this test.
*Tonometry: This is a standard test to measure fluid pressure inside the
eye. Increased pressure may be a sign of glaucoma.
Other eye tests may also be used occasionally to show how poorly you see
with a cataract or how well you might see after surgery:
A. Glare test B. Contrast Sensitivity Test C. Potential
Vision Test D. Specular Photographic Microscopy
How Cataract can be Treated?
(A) For an early cataract, vision may improve by using different eyeglasses,
magnifying lenses, or stronger lighting. If these measures don't help,
surgery is the only effective treatment. This treatment involves removing
the cloudy lens and replacing it with an artificial lens. A cataract needs
to be removed only when vision loss interferes with your everyday activities,
such as driving, reading, or watching TV.
(B) Surgery is the only option for Cataract. Neither diet nor medications
have not been shown to stop cataract formation. Cataract surgery is now
a frequently performed operation in most parts of the world
Cataract Surgery Methods:There are two primary ways to remove a cataract.
*Phacoemulsification, or Phaco (Misnomered as Laser): Your doctor makes
a small incision on the side of the Cornea, the clear, dome-shaped surface
that covers the front of the eye. The doctor then inserts a tiny probe
into the eye. This device emits ultrasound waves that soften and break
up the cloudy center of the lens so it can be removed by suction. Most
cataract surgery today is done by phaco, which is also called small incision
cataract surgery or Suturless surgery. Since the incision is made in a
valvular fashion with the help of special keratomes, there is no need
to take any stitches & the incision takes only a couple of hours to
heal.

Click
here for video clip of cataract operation with foldable lens (Phacoemulsification)
---Need real player download here---
"
Extra capsular surgery. Your doctor makes a slightly longer incision on
the side of the cornea and removes the hard center of the lens. The remainder
of the lens is then removed by suction.In a cataract operation, the eye's
natural lens is removed. In most cataract surgeries, the removed lens
is replaced by an artificial Intra-Ocular lens (IOL). An IOL is a clear,
artificial lens that requires no care and becomes a permanent part of
your eye. With an IOL, you'll have improved vision because light will
be able to pass through it to the retina.for som people with eye disease,
a soft contact lens may be suggested. For others, glasses that provide
powerful magnification may be better.
The artificial
lens is made of plastic and is usually inserted at the same time the cataract
is removed. Once the surgeon has determined that intraocular lens replacement
is appropriate, the patient undergoes a special preoperative evaluation.
Like contact lenses and "prescription" eyeglasses, intraocular
lenses differ in terms of refractive power, and the evaluation will determine
the proper lens power of the implant. The length of the eye is measured
and the curvature of the cornea is evaluated. Calculation of the implant
power is based on this information and performed on a computer called,
A-scan Biometry or Sonography.
Generally speaking, overall cataract surgery lasts about an hour and is
usually performed on an outpatient basis. After a brief rest after surgery,
the patient generally returns home the same day, in most of the cases
without a Bandage too ( more so if the surgery is done under typical anesthesia
& a foldable lens is implanted.
Types of Intra-Ocular Lens :
(1) Foldable
(2) Expandable (3) Non-foldable (4) Multifocals
GLAUCOMA
What is Glaucoma?
*Glaucoma is a disease where the pressure inside the eye is raised to
the extent that it may cause visual damage. So it is an abnormally high
fluid pressure within the eye. As pressure builds, it can "pinch"
both the optic nerve and the blood vessels, which nourish the retina.
The result is usually a slow loss of peripheral, or side vision, and eventual
blindness. So Glaucoma is the leading preventable cause of blindness.
* Generally our eye needs a certain amount of pressure to keep the eyeball
in shape so that it can work properly. In some people, the damage is caused
by raised eye pressure. Others may have an eye pressure within normal
limits but damage occurs because there is a weakness in the optic nerve.
In most cases both factors are involved but to a varying extent. Eye pressure
is largely independent of blood pressure.

Types of Glaucoma:
A. Open
Angle glaucoma
B. Closed Angle glaucoma
C. Secondary glaucoma (precipitated by other factors)
D. Primary glaucoma (glaucoma originating without secondary
causative
factors)
E. Juvenile glaucoma (children)
F. Congenital glaucoma (meaning from birth)
In Open-angle glaucoma, the transparent fluid inside the eye (Aqueous
Fluid) cannot be drained quickly enough, because the drainage channels
(Trabecular meshwork) within the eye have become restricted. Open-angle
glaucoma is often inherited from parents, although this is rarely the
case with Closed-angle glaucoma.
In Closed-angle glaucoma, the angle or periphery of the anterior chamber
of the eye is closed and so the eye cannot drain the fluid quickly enough.
The most common is chronic glaucoma (chronic = slow) in which the aqueous
fluid can get to the drainage channels (open angle) but they slowly become
blocked over many years. The eye pressure rises very slowly and there
is no pain to show there is a problem, but the field of vision gradually
becomes impaired.
Acute glaucoma (acute = sudden) happens when there is a sudden and more
complete blockage to the flow of aqueous fluid from the eye. This is because
a narrow `angle' closes to prevent fluid ever getting to the drainage
channels. This can be quite painful and will cause permanent damage to
your sight if not treated promptly.
Childhood glaucoma
Childhood glaucoma is a rare form of glaucoma that often develops in infancy,
early childhood, or adolescence. Prompt medical treatment is important
in preventing blindness.
Congenital glaucoma
Congenital glaucoma, a type of childhood glaucoma, occurs in children
born with defects in the angle of the eye that slow the normal drainage
of fluid. Prompt medical or surgical treatment is important in preventing
blindness.
Primary glaucoma
Both open-angle and angle-closure glaucoma can be classified as primary
or secondary. Primary glaucoma cannot be contributed to any known cause
or risk factor.
Secondary glaucoma
Both open-angle and angle-closure glaucoma can be classified as primary
or secondary. Secondary glaucoma develops as a complication of another
medical condition or injury. In rare cases, secondary glaucoma is a complication
following another type of eye surgery.
Symptoms of Glaucoma:
* Frequent mild headaches, especially upon waking;
* Increased difficulty with night vision;
* Recurring redness in one or both eyes, especially if accompanied by
blurred vision
and/or pain.
* A frequent change of eyeglass prescriptions;
* A noticeable loss of peripheral vision.
* Severe eye pain, foggy vision and rainbow haloes.
If you experience
these symptoms, seek treatment immediately.
Main Cause for Glaucoma:
The main underlying reason why increased intra ocular pressure develops
(glaucoma) is because the outflow of intra ocular fluid gets impaired
(obstructed) in one way or another. This leads to increased pressure of
the fluid inside the eye.

* Anyone can develop glaucoma, however, it is rare in people under 45
years of age. The people, who run the highest risk of developing glaucoma,
are people who have a close blood relative who have suffered from glaucoma.
(E.g. mother, father, sister or brother)
" Certain eye conditions are more prone to developing glaucoma: --
- People who are very short-sighted
- Detachment of the Retina.
- Certain illnesses of retina e.g. Retinitis pigmentosa
- Also patient with diseases of the thyroid gland.
- Patient with Diabetes mellitus (impaired Sugar tolerance)
Detection & Diagnosis of Glaucoma:
Glaucoma can only be detected through a series of tests performed by your
eye doctor. The loss of vision is usually so gradual and painless that
most people are unaware of it until damage is permanent. Once vision has
been lost due to glaucoma, it cannot be restored. If you are over 45 years
of age, your eye surgeon will use an instrument called a "Tonometer".
This instrument takes a pressure reading from your eye by placing the
machine on your eye (Applanation or Schiotz Tonometer) or by firing a
puff of air (Pneumotonometer).
In addition to a complete medical history and eye examination, your eye
care professional may perform the following tests to diagnose glaucoma:
* Visual acuity test - the common eye chart test, which measures vision
ability at various distances.
* I.O.P. Measurement - Either by Schiotz Tonometer (lying down position)
or by Applanation or Pneumotonometer (sitting position on the slit lamp)
* Pupil dilation - the pupil is widened with eye drops to allow a close-up
examination of the eye's retina & optic nerve head.
* Gonioscopy - To see the angle of the eye with the help of 3 or 4 mirror
Gonioscope.
* Visual field - a test to measure a person's side (peripheral) vision.
Lost peripheral vision may be an indication of glaucoma.
In a simple, painless test, doctor measures the fluid pressure or "hardness"
of the eyeball manually and evaluates the retina and optic nerve. If the
pressure is unusually high or if the optic nerve proves abnormal upon
examination, your doctor will probably suggest you undergo a "visual
fields" test to determine if any peripheral or side vision has been
lost.
Treatment of Glaucoma:
If glaucoma is detected, it can be treated one of three ways: with medications,
conventional surgery or lasers. Traditional treatment includes eye drops
and tablets to control fluid pressure. These drugs will reduce the production
of the transparent fluid within the eye. This relieves the pressure from
within the eye and prevents damage caused by Glaucoma. If medication is
ineffective, either laser or conventional surgery will be used to open
channels in the eye through which fluid may drain.
"The best defense against glaucoma is regular eye checkups by a qualified
eye care specialist."
LASER:
The laser, actually an intense beam of light, produces short bursts of
precisely directed energy to create fluid channels within the eye. A typical
laser treatment takes 15 minutes or less and requires only eye drops for
anaesthesia. Blurred vision for an hour or so after Laser is usually the
only discomfort. The laser is not a "cure" for glaucoma, but
it often makes it possible to avoid surgery and reduce dependence on medications.
If laser and medical treatment fails to bring glaucoma under control,
conventional glaucoma surgery to open a drainage channel will almost certainly
be required.
TRABECULAR SURGERY:
This method is used to improve the drainage of fluids from the eye. The
"trabecular meshwork" is a fine net of fibers between the cornea
and the iris. If fluid is blocked from passing through this net, pressure
on the eye builds, pinching the optic nerve.
The surgery is usually done under local anaesthesia. The usual surgical
time is around 30-35 minutes. Bandage is kept for a day or two depending
on the healing. Slight pricking or watering & redness following surgery,
will be there for 5-7 days. Though the complication rate is less, but
few complications viz. bleeding, failure of surgery or loss of vision
may be expected in less than 1% of cases.
DIABETIC
RETINOPATHY
Normal
Vision:
The Retina
is the nerve cell layer of the eye and acts much like film in a Camera.
When light enters the eye it passes through the Cornea and Lens and is
focused onto the Retina. The Retina transforms the light energy into vision
and sends the information back to the brain through the optic nerve. The
macula is the sensitive, central part of the retina and is responsible
for sharp, detailed vision.
DIABETIC
RETINOPATHY:
Diabetic
Retinopathy results from the effects of the diabetes on blood vessels
that nourish the Retina tissue, which is the innermost layer of the eye
wall. It is mainly associated with diabetes and is caused by the breakage
of tiny blood vessels in the retina, causing hemorrhages on or in the
retina. Diabetes causes retinal blood vessels to leak and grow abnormally.
Untreated diabetes or poor disease maintenance greatly increases the risk
of diabetic retinopathy. Depending on the severity of the disease, sight
can remain near normal or may be lost entirely. Remaining vision may be
blurred or distorted or the hemorrhage may cause a deep reddish veil to
form over the field of vision
.
Types of Diabetic Retinopathy:
A. Non-Proliferative
B. Proliferative.
* In Non-Proliferative
or Background Diabetic Retinopathy, patients may have normal vision. The
damaged retinal vessels leak fluid. Fat and protein particles may leak
from these vessels and become deposited in the retina in patches known
as retinal exudates. The retinal blood vessels may bleed into the retina
and result in tiny hemorrhages. If any of the leaking fluid accumulates
in the central part of the retina (called the macula), the vision is affected.
This condition is called Macular Edema.

* In Proliferative Diabetic Retinopathy, new abnormal blood vessels grow,
which extend over the surface of the retina. These vessels occasionally
invade the gelatinous contents of the eye, the vitreous. The proliferating
blood vessels frequently break, causing vitreous bleeding that may significantly
decrease vision. Fibrous tissue may grow over the new blood vessels and
distort vision. Occasionally, the tissue may contract and pull the retina
off the inner surface of the eye, causing a tractional retinal detachment.

Symptoms:
There are no symptoms in the early stages of diabetic retinopathy. Vision
may not change until the disease is advanced or the Macula is affected.
The earliest sign may be an abrupt change in eyeglass prescription. The
blood sugar effects the water content of the lens of the eye and, therefore,
spectacle prescription changes. Sudden increase in blood sugar will cause
an increase in myopia. This often occurs before the detection of the disease.
Diabetic Retinopathy may begin in eyes without one noticing any change
in vision. Unfortunately, there may be extensive and severe changes before
vision is affected. Thus, it is very important to have the eyes examined
regularly at six-month or yearly intervals
depending on duration and/or severity of the diabetes.

Detection of Diabetic Retinopathy:
Diabetic Retinopathy is detected during an examination of the back of
the eye "Fundoscopy" through dilated (enlarged) pupils and by
testing your vision. Dilation is the method through which after putting
some eye drops we can see what is inside, to properly evaluate the Retina.
We look for evidence of Diabetic Retinopathy. Based on the findings a
Fluorescein Angiogram may be advised.
Fundus
Fluorescein Angiography (FFA):
Fluorescein Angiography is a dye test often used to assess the damage
to the retina and its blood vessels. A dye is injected into a vein of
one arm. Photographs are taken of the retina as the dye passes through
the blood vessels. Since there is a risk of allergic reaction, a history
of allergy is important. There may be mild nausea during the procedure.
The skin and urine may turn yellow for 24 to 48 hours. These Angiograms
show areas of leakage, areas of oxygen-starved retinas, and weak, fragile
new vessels. Based on the results a laser may be advised.
Treatment:
LASER:
The most important treatment for diabetes and its complications including
diabetic retinopathy is control of the diabetes. Tight control of blood
sugar, weight and blood pressure are important in preventing the ocular
complications of diabetes and thus slowing the progression of the disease.
Once retinopathy is diagnosed, LASER therapy is the current modality of
treatment. Most patients tolerate the procedure extremely well with little
discomfort. Laser surgery is used to treat both diabetic macular edema
and proliferative diabetic retinopathy. Laser treatment for diabetic macular
edema stabilizes vision by stopping blood vessels from leaking fluid into
the retina. Either focal treatment for small discrete areas of leakage
or a grid pattern is used when the leakage is diffuse in nature. After
treatment, the patient may notice small spots of decreased visual sensitivity
in the field of vision. Usually these spots become less noticeable with
time. It is possible that the vision may get a little worse after laser.
However, the laser helps prevent further reduction in vision. Studies
have shown that most patients who receive laser for macular edema will
have better vision in the future than if they hadn't received the treatment.
After instilling an anaesthetic drop in the eye, the retina is treated
with LASER using suitable laser delivery system.
RETINAL
DETACHMENT
In Retinal
Detachment, the retina separates from the outer layers of the eye thus
losing its function. If not treated early, retinal detachment may lead
to impairment or complete loss of vision.
Cause:
Most retinal detachments are preceded by one of more tears or holes in
the retina. Fluid passes through these openings and separates the retina
from the adjacent layers of the eye. Near-sighted individuals are more
commonly affected due to thinning of the retina. Holes or tears can then
develop in the thinned retina. The vitreous (gel fluid in the eye) also
plays a significant role by causing tugging on the retina especially when
shrinkage occurs. Cataract surgery can also be a precipitating cause.
A positive family history of retinal detachment is another risk factor.
A combination of factors is usually responsible for retinal detachment.
Retinal detachment can also be caused by other diseases in the eye such
as tumors, severe inflammations, or complications of diabetes.
Symptoms:
Middle-aged and older persons may see floating black spots called floaters
and flashes of light. In most cases, these symptoms do not indicate serious
problems. In some eye, the sudden appearance of spots or flashes of light
may herald the onset of retinal detachment. A thorough examination of
the retina by an Ophthalmologist after dilation of the pupil is necessary
to determine the cause of the symptoms. Some retinal detachments can proceed
unnoticed until a large section of the retina is detached. In these instances,
patients may notice the appearance of a dark shadow in some parts of their
vision. Further development of the retinal detachment will blurr central
vision and create significant sight loss in the affected eye. A few detachments
may occur suddenly and the patient will experience a total loss of vision
in that eye. Similar rapid loss of vision may also be caused by bleeding
into the vitreous, which may happen when the Retina is torn.
Treatment:
If the retina is torn but detachment has not yet occurred, prompt treatment
may prevent the occurrence of a complete detachment. Once the retina becomes
detached, it must be repaired surgically.
Laser
Photocoagulation:
When new small retinal tears are found with little or no nearby retinal
detachment, the tears are sometimes sealed with a laser light. The laser
places small burns around the edge of the tear. These produce scars that
seal the edges of the tear and prevent fluid from passing through and
collecting under the retina.
Freezing
or Cryopexy:
Freezing through the sclera (white of the eye) behind a retinal tear will
also stimulate scar formation and seal down the edges.
Surgical
Repairs:
Successful reattachment of the retina consists of sealing the retinal
tear with a silicone material, which is sutured to the Sclera (white of
the eye) to indent the eyeball inwards. Freezing applications are then
used to bind the retina to the underlying layers.
Newer procedures
have been developed to achieve the same result using the injection of
a gas into the eye in suitable cases.
The surgery
may be performed under local or general anaesthesia depending on the procedure,
age and general health of the patient. In more complex retinal detachments,
it may be necessary to use a technique called vitrectomy. This operation
removes the vitreous body from the eye. In some cases, when the detached
retina itself is severely shrunken or scarred, air or gas may have to
be used to fill the vitreous cavity temporarily.
Prognosis:
Over 90%
of all retinal detachments can be reattached by modern surgical techniques.
Occasionally, more than one operation may be required.
The degree
of vision which finally returns about six months after successful surgery
depends upon a number of factors. In general, there is less visual return
when the retina has been detached for a long time or if there is fibrous
growth on the surface of the retina.
Approximately
40% of successfully treated retinal detachments achieve excellent vision.
The remainder attains varying amounts of reading vision.
Due to continuous
shrinkage of the vitreous and the development of fibrous growths on the
retina, not all retinas can be attached. If the retina cannot be reattached,
the eye will continue to lose sight and ultimately become blind.

Before Operation
|
After
Operation
|
LASIK
What is Refractive Error?
The cornea is a part of the eye that helps focus light to create an image
on the retina. It works in much the same way that the lens of a camera
focuses light to create an image on film. The bending and focusing of
light is also known as Refraction. Usually the shape of the cornea and
the eye are not perfect and the image on the retina is out-of-focus (blurred)
or distorted. These imperfections in the focusing power of the eye are
called Refractive errors.

Normal Eye Vision
Type of Refractive Errors:
There are three primary types of refractive errors: Myopia, Hyperopia
and Astigmatism.
1. Myopia (Near-Sightedness): -
In a "Myopic" eye, the light rays are passed
through the "Cornea" & "Lens", but point at which
they get focused is in front of "Retina". This
Configuration allows clear image of near objects, but not those that are
far away. Normally, it occurs, when "Cornea" is too curved or
eye is too long.
2.Hyperopia (Far-Sightedness): -
In case of "Hyperopic"
eye, light rays after getting passed through "Cornea" &
"Lens", focus at a point beyond the "Retina". In such
case, patients can focus more on distant object, but not images that are
close to hand. It occurs when cornea is too flat or the eyeball is too
short.
3. Astigmatism: -
With Astigmatism, the rays of light do not focus into a single point but
form a line on Retina. This occurs when the corneal curvature is irregular
in different meridians.
Types
of Refractive Surgery:
Various
types of Refractive Surgery that are used to reshape the "Cornea"
are:
1. Radial
Keratotomy (RK)
2. Photo Refractive Keratotomy (PRK)
3. Laser In-Situ Keratomileusis (LASIK)
In "RK",
a very sharp knife is used to cut slits in the "Cornea" changing
its shape.
"PRK"
was the first surgical procedure developed to reshape the cornea, by sculpting,
using a laser. It involves removal of the top surface layer of the cornea
called the epithelium. This exposes the inner cornea (stroma), which the
computer assisted laser will begin to resculpt, thereby altering the curvature
of the Cornea.
Later the
"LASIK" was developed. The same type of Laser is used for both
"LASIK" & "PRK". The major difference between
these two procedures is the way in which the stroma (the middle layer
of the "Cornea") is exposed before it is vaporized with the
laser. In "PRK", the top layer of "Cornea" (called
Epithelium) is scraped away to expose the stromal layer underneath, while
in LASIK, a flap is cut in the stromal layer & the flap is folded
or replaced back.
LASIK
Fundamentals: -
What
is LASIK?
LASIK is the acronym for "Laser In-Situ Keratomileusis". It
is a surgical procedure that is capable of correcting a wide range of
"Near-sightedness", "Far-sightedness" & "Astigmatism"
by the use of laser to reshape the "Cornea" without invading
the adjacent cell layers. This correction procedure utilizes two devices
i.e. the Excimer Laser and the Microkeratome. The Microkeratome, a precise
instrument that is the "keystone" in the LASIK procedure, is
a mechanical shaver that contains a sharp blade that moves back and forth
at high speed. This shaver is placed in the guide tracks of the suction
ring and is advanced across the cornea using gears at a controlled speed.
This process creates a partial flap in the cornea of uniform thickness.
The flap is created with a portion of the cornea left uncut to provide
a hinge.
Why
LASIK?
LASIK is the latest Refractive Surgery technique that can benefit a great
number of people with Myopia, Hyperopia & Astigmatism. Candidates
who have a strong desire to reduce a lifetime dependence on glasses &
contact lens can go for LASIK.
Comparison of Refractive Surgery:
Neither LASIK nor PRK involves any pain during the procedure itself. Patients
prefer the LASIK procedure because of the rapid vision recovery and minimal
postoperative care.Patients with high amounts of nearsightedness should
have LASIK. For patients with lower to moderate amounts of myopia, either
process may be appropriate, of course let your refractive surgeon decide
what is best for you.
PRK
|
LASIK
|
1.Preferred
for lower degree of Myopia & Hyperopia. |
1.Treats
high level of Myopia & moderate amount of Hyperopia & Astigmatism. |
2.
Slow Visual Recovery. |
2.
Visual recovery is faster. |
3.
Outcome depends on healing ability of the Patient. |
3.
Gives better results with higher
predictability, so number of follow-ups are reduced. |
4.
Procedure is relatively Painful. |
4.
Procedure is Painless. |
5.
Laser is given after scraping the epithelium of the Cornea. |
5.Laser
is given under the corneal flap.Epithelium remains intact and therefore
better visual results. |
6.
Eye medications are used for 2-3 months and clear contact lenses are
placed on each eye for 3-5 days to prevent infection. The surface
layer will begin to regenerate itself and the whole healing process
will take up to 3-4 mths. |
6.
Eye drops used for up to one week and the patient can resume normal
activities within three days. Most of the healing] process takes place
within a week, however, it may take from 1 to 3 months for your vision
to fully stabilize. |
7.
Pain relief medications required for about 1-2 days post operatively.
|
7.
Many LASIK patients experience only 5-6 hours of discomfort. |
8.
With PRK there is a small risk of problems arising from an irregular
healing response and/or infection. These can generally be treated
with medications or in some cases by further surgery. |
8.
The disadvantage of LASIK is that it requires an additional surgical
step, the creation of the flap. This creation is painless and takes
less than a minute to complete. Improper creation of the flap could
result in the need for further surgery |
Step
by step Operation procedure of LASIK:
In a nutshell,
LASIK procedure requires the surgeon to use a surgical instrument called
a Microkeratome to create a corneal flap. A portion of the flap remains
attached to the eye (as a hinge) while the remainder is gently lifted
up and back exposing the inner cornea. The cool beam laser resculpts the
cornea and the flap is then returned to its original position.
Step
1:
Anaesthetic eye-drops are instilled to numb the eye & after that surgeon
marks the "Cornea" to guide replacement of the flap.
Step
2:
With the help of a specially designed "Suction Ring" ,Surgeon
holds the eye steady & checks the pressure of the eye.
Step
3:
With the help of "Microkeratome", Surgeon raises a thin layer
of Cornea called Corneal Flap, to expose the portion beneath.
Step 4:
The flap of around 1/5 of the thickness of Cornea is lifted and reflected
to the side.
Step
5:
Then as a basic preparation, Surgeon walks the patient through the fixation
process & also tests for laser alignment.You will be asked to look
at the target light while the Laser is on.
Step
6:
The Excimer laser now removes the tissue under the flap.
Removal
of lap
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Excimer
laser
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Removal
of lap.
A clicking sound can be heard as each microscopic layer of tissue is vapourized.
The process will last from seconds to minutes depending upon the amount
of correction required.Ultraviolet light & high-energy pulses from
excimer laser reshape the cornea with accuracy up to 0.25 micron.
Step
7:
Then, the surgeon lays the flap back into its original position. Healing
is rapid and the eye does not require stitches or bandage or contact lens.
Near-Sightedness (Myopia) Correction:
If nearsightedness is being corrected, the Excimer Laser is used to remove
tissue and reshape the center of the cornea. The amount of tissue removed
is dependent upon the degree of near-sightedness that is being corrected.
Astigmatism Correction:
The Excimer laser can be used to treat astigmatism while performing LASIK.
Astigmatism measurements describe to what degree the cornea is "non-spherical."
As an example, the surface of a basketball is spherical and would have
no astigmatism. The surface of a football, on the other hand, would be
highly non-spherical and would have high astigmatism. The Excimer laser
reduces the degree of astigmatism by removing corneal tissue in an asymmetric
manner, utilizing an oval-shaped beam.
Far-Sightedness
(Hyperopia) Correction:
If farsightedness (hyperopia) is being corrected, the cornea is flatter
than is required given the length of the eye. Hyperopic LASIK is used
to reshape the front surface of the eye, making it more curved. In hyperopic
(farsighted) treatment, a "donut" of tissue is removed from
the mid-periphery of the cornea. This changes the profile of the cornea
to steeper the central curvature.
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