Fc Assignment

7/27/2019 Fc Assignment

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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.

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