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FC ASSIGNMENT
NAME: KHUSHBOO .H. JAIN
CLASS: SYBCOMC
ROLL NO.: 02
TOPIC: LASER EYE TECHNOLOGY
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Laser Eye Technology
QuickHistory:
Corrective eye surgery has been in practice since the 1940s. Radial
keratotomy (RK) and photorefractive keratectomy (PRK) have had the greatest
impact on current methods of refractive eye surgery. The most common
refractive surgery used today is Laser in Situ Keratomileusis (LASIK). RK uses a
diamond tipped knife to flatten the central cornea by making a series of incisionsradiating from the cornea. RK can only treat low degrees of myopia and
astigmatism, unlike LASIK. PRK uses a laser to correct the refractive area by
removing corneal tissue. PRK can be discomforting or even painful because it
removes nerve fibers that run through the corneal epithelium. After this surgery,
it can take up to six months for vision to stabilize. Immediately following the
surgery, vision is blurry until the corneal epithelium healed, and the bandage lens
removed. PRK is similar to LASIK because it uses a laser to correct the corneal
defects. LASIK has the same benefits, but with fewer, less-sever side effects thanPRK. Also, LASIK is less painful, and recovery time is shortened because the
corneal epithelium is not removed. The LASIK procedure folds back the corneal
epithelium and then a laser is used to reshape the cornea.
The first lasers used were broad beam lasers (about 6 mm) that acted similar to a
showerhead, splitting the main laser into smaller beams.
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The Role of Physics in Laser Eye Surgery:
The deficiency of the eye can be examined using the physics of
refraction. Refraction occurs mostly at the cornea due to the substantial
difference between the index of refraction of the cornea, and that of air. The
cornea and the lens combine to focus the light at the retina. The eye adjusts the
curvature of the lens in order to alter the focal length, enabling it to focus objects
at varying distances. A normal eye is able to converge light properly by changing
the lens shape so that objects both near and far appear clearly.
In nearsightedness, the cornea is overly curved resulting in a greater index of
refraction. The light converges, and the image forms in front of the retina. In
order to correct this problem with laser eye surgery the procedure begins with a
surgeon temporarily peeling back the epithelium. A laser is then trained on the
eye to remove small amounts of the cornea. The cornea is flattened in order to
correct nearsightedness. The flattened cornea has a lower index of refraction
than previously, focusing the image on the retina instead of in front of the retina.
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Another dysfunction of the eye is farsightedness. In farsightedness, the
cornea is not curved enough, and thus, the refractive index is lower. This causes
the images focal point to be located behind the retina. The surgeon corrects thiscondition by using a laser to remove the outer edge of the cornea, thus
steepening it. As a result of this surgery, the eye is able to focus the image
directly on the retina, due to the greater index of refraction resulting from the
curvature of the eye being increased.
Advantages, Disadvantages, and Risks:
Laser eye surgery is one of the fastest methods to correct visual impairments. It
has the ability to correct even severe refractive errors, but minimize the recovery
time. Most patients are able to return to work within a week! Many patients even
return to normal activities the day after surgery. The treatment is permanent
according to studies done so far, but as eyes change with age re-treatment may
be necessary over time. Eye drop medication is necessary for the first week, butdiscomfort wears off after 5-6 hours. The medication is used to prevent infection,
not as a pain suppressant. The main disadvantage of LASIK surgery is that it
requires the creation of a flap in the cornea. This step takes less than a minute to
complete, but there are risks of complications.
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As with any surgery, there are risks associated with the procedure. The best way
to avoid certain risks is to have a thorough examination with your doctor pre-
surgery. Some of these risks of surgery include:
Corneal infection (less than 0.1% with LASIK)
Undercorrection/overcorrection
Decrease in best corrected vision
Corneal haze, though risk is less with LASIK than PRK
Regression, can be re-treated to correct, etc.
What to Expect:
The first step to having laser eye surgery is a medical examination with your
doctor to determine your prescription, look for any retinal problems or unusual
intraocular pressure, and look for signs of eye disease. A corneal topographer is
used to make a map of your cornea to help the surgeon determine how to correct
the irregularities. Before you go in for surgery, be sure to not wear any contact
lenses for a week because that changes the shape of the cornea. Also dont use
makeup or lotions around the eyes.
During surgery, which lasts approximately 30 minutes, you will lie on your
back and numbing drops are placed in your eye. A lid speculum holds the eye
open as it is cleaned and high pressures are applied to create suction around the
cornea. The doctor uses a microkeratome, a blade, to cut a flap into the cornea.
Then the suction ring is removed. The flap is folded back and a laser positioned
over your eye. The doctor will ask you to fixate on a point of light, then use a laser
to remove the corneal tissue. Pulses are heard as the computer programmed
laser removes a fixed amount of tissue determined by pre-operationmeasurements. A shield is placed over the eye to prevent damage to the eye or
movement of the flap, as no stitches are used. The pressure from the eye will
cause the flap to reseal against the eye and it will heal naturally.
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After surgery, there may be slight discomfort, which can typically be
removed by a mild over the counter pain reliever. These symptoms should
disappear within the first few days. A follow up appointment is absolutely
necessary the day after surgery to ensure the flap has not been dislodged and is in
the appropriate place. After that, check-ups on regular intervals for only six
months. Vision may fluctuate during the months after surgery but should stabilize
within three to six months.
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Who should get laser eye surgery?
Laser eye surgery is ideal for anyone who wants the freedom that improved
eyesight can give. The hassles of glasses and corrective lenses can be removed,
often permanently, by the procedure. But, laser eye surgery is not for everyone.Before undergoing surgery, all patients should have a complete medical
examination with their doctor. People with persistent medical conditions, have
difficulties healing, or have vascular, autoimmune, or eye diseases may not be
suitable for the procedure. Pregnant women should also refrain from surgery due
to changes in the eyes refraction during pregnancy.
Typical patients for eye surgery are at least over 18, though the age
preference changes with the type of laser used. Patients have mild to moderate
nearsightedness, farsightedness, and astigmatisms, within the range of correction
for the treatment. Each laser has different ranges for the procedure performed.