Wednesday 30 October 2013

Lasik surgery for Myopia

What is it? 

LASIK (laser assisted in-situ keratomileusis) surgery is an operation that is done to correct near-sightedness (myopia) by using laser light.

The cornea is the clear/transparent film in the front of the eye that lies just in front of the coloured part which is the iris. The cornea allows light to enter the eye and also refracts/bends the light and focuses it at the back of the eye which is the photosensitive area called the retina.

If there is a problem with the shape of the cornea, the light focuses in front of and not exactly on the retina and this doesn’t allow you to clearly see objects that are away from you.
In LASIK surgery, the cornea is properly reshaped by the laser to allow the light to focus on the retina. LASIK surgery can be used for people with mild, moderate or severe myopia.

It’s not indicated for people who:

• are aged less than 18 years.
• have not had stable vision for at least one year.
• have any other diseases of the cornea.

 Although nearsightedness is the main indication for LASIK surgery, it has also been used to a much lesser degree for the correction of hypermetropia and astigmatism.

In hypermetropia (far-sightedness) the cornea focuses the light behind the retina, while in astigmatism the light has a split focus which results in blurred vision.

The operation

The operation takes about 30 minutes and is carried out as a day surgery case, which means that you will go home on the same day of the operation. The operation takes place in a room that has the Laser system.
You will be on a special chair that is similar to a dentist’s chair. You will be lying on your back and your eye will be numbed with some anaesthetic eye drops. A special device is used to keep the eyelids open.

A microscopic knife will be used to cut a small flap in the centre of the cornea. The cut is not complete; a small bridge of tissue is left to keep it in contact with the rest of the cornea. The flap is then lifted and folded back.

Via this opening the laser light can get through to the inner aspect of the cornea. The laser system will then be positioned close to your eye and the laser light will be directed towards the inner aspect of your cornea.

The laser light vaporises the tissue of the inner aspect of the cornea and reshapes the cornea in such a way that after the operation it will focus the light on the retina allowing you to clearly see objects that are away from you.

The amount of laser light/energy that will enter your eye and the way it will reshape the cornea is controlled by a computer which is very accurate.

After the laser treatment the flap of the cornea is put back in place but it is not stitched. A pad/shield will be placed over the eye at the end of the procedure to protect it.

Any alternatives?

This is an entirely elective procedure that is being done to help you to get rid of the inconvenience of wearing spectacles/glasses or contact lenses.

lasik Surgery
lasik Surgery
You don’t have to have LASIK surgery and therefore, you need to have a very detailed discussion with your ophthalmologist before you decide to have the procedure.

Before the operation

Stop smoking and get your weight down if you are overweight.
If you know that you have problems with your blood pressure, your heart or your lungs, ask your family doctor to check that these are under control.

Check the hospital’s advice about taking the Pill or hormone replacement therapy (HRT). Bring all your tablets and medicines with you to the hospital.

If you take aspirin or any other medication that contains aspirin, you’ll need to let your doctor know. You need to stop taking it one week before the operation because aspirin is a blood-thinner and can cause bleeding.

On the ward, you will be checked for past illnesses and will have special tests to make sure that you are well prepared and that you can have the operation as safely as possible. You will have the operation explained to you and will be asked to fill in an operation consent form.

Before you sign the consent form, make sure that you fully understand all the information that was given to you regarding your health problems, the possible and proposed treatments and any potential risks. Feel free to ask more questions if things are not entirely clear.

Any tissues that are removed during the operation will be sent for tests to help plan the appropriate treatment. Any remaining tissue that is left over after the tests will be discarded.

Before the operation and as part of the consent process, you may be asked to give permission for any ’left over’ pieces to be used for medical research that have been approved by the hospital. It is entirely up to you to allow this or not.

Many hospitals now run special preadmission clinics, where you visit a week or so before the operation, where these checks will be made.

If you are using contact lenses, you need to stop wearing them three to four weeks before the operation and use glasses instead. This is because contact lenses affect the shape of the cornea and it needs three to four weeks to revert to its natural shape. If the cornea does not have its natural shape before the operation, the laser cannot reshape it accurately and effectively to provide a successful result.

After – in hospital

Most patients experience little pain or discomfort after LASIK surgery but may have some minor swelling of the eye. You may be given painkillers to control the pain or discomfort.
Your eye may also itch or produce tears. Don’t rub it!

You can wash, bathe, or shower normally after the operation, but you must not get water in your eye for a month. If you have your hair washed, have it done with your head leaning backwards. Do not use makeup on your eyelids for one month.

You will be given a supply of eye drops and be shown how to put them in your eye. The drops are used to prevent infection.

You will be given an appointment for the outpatient department for your first check-up one to two days after your operation. From then on you will have regular appointments (the frequency depends on your progress) for six months after your operation.

The nurses will advise about sick notes, certificates, etc. You are advised to have somebody with you to drive you home.

After – at home

At home, if you experience some mild discomfort or pain in the area of the operation, take two painkillers every six hours to control it. It is better to take paracetamol and not aspirin, which can cause bleeding.
Even if everything is well during your first visit as an outpatient one to two days after your operation, you will continue to have your eye covered by a pad and a protective plastic shield. This is to stop you touching your eye, especially when you are asleep.

You MUST wear the eye shield to protect the operated eye at night, or if you sleep during the day. You will be told in the outpatient clinic when you can stop using the shield (normally about one month).
During the day you can use any glasses you were using before the operation.Sunglasses are a good idea to protect your eyes from the glare. You must not use contact lenses.

After the operation any activity that can jolt the eye must be avoided. Contact sports must be avoided after LASIK surgery for at least four to six weeks.
Plan to go back to light work in about two to three weeks, and a more heavy/manual job after about three to four months.

Initially, your vision might be blurry for the first few days after the operation but it will gradually improve. It usually takes three to six months to experience the maximum improvement and stability of your vision.
You must be very careful with driving because your sight may not be as good as you think it is. Ask the doctor whether your sight is good enough to drive. If in doubt, don’t drive.

Possible complications

Complications occur in 1 to 5 per cent of cases.

The eye may become infected in the area of the operation. Drops of antibiotics and of anti-swelling medication may be needed to treat the infection. If the infection is very serious and spreads around your bloodstream, you will need to stay in hospital and have the infection treated by intravenous (antibiotics through a small plastic tube placed in one of your veins).

You may also experience the problem of dry eye which can cause irritation, redness and discomfort. This is treated by using eye drops that help to keep the area wet until the symptoms go away.
The dislocation of the flap after the operation can be a problem which has to be treated promptly with another operation to put it back in place before it affects vision.

Sometimes, while the cut around the flap is healing, a lot of scarred tissue can develop and this can blur your vision. You may need further laser treatment or another operation to deal with this problem, but this is not always successful.

LASIK surgery can sometimes under-correct or over-correct the problem of myopia or, rarely, can make it worse. In this situation you may require further laser treatment but there is a chance that the result will not be successful.

LASIK surgery significantly improves the vision of 80 to 90 per cent of people with less than 6 diopters (a unit used to measure how well a person sees – the more the diopters the worse the vision) of myopia.
The procedure results in significantly better vision in 30 to 60 per cent of people with 6 to 12 diopters of myopia.

General advice

These notes should help you through your operation. They are a general guide. They do not cover everything. Also, all hospitals and surgeons vary a little.

If you have any queries or problems, please ask the doctors or nurses.

Thursday 24 October 2013

Types of Laser Eye Surgery


There are two fundamentally different types of laser eye surgery: PRK and LASIK. Under these two categories, there are several different flavors or modifications of each type. For example, LASEK (with an “E”) is just a newer type of PRK. All techniques are performed with the patient awake and drops are used to numb the eyes.
The types of laser eye surgery that fall under the category of PRK do so because they all involve a surface ablation technique to remove the cornea’s outermost layer, called the epithelium, rather than creating a flap via a cutting technique as used in LASIK procedures. Removing the epithelium is the first step of laser eye surgery. The next step is reshaping the cornea by excimer laser. Here, the model of excimer laser varies as do guidance or mapping systems associated with each model. The more precise the mapping and reshaping system, the better the results.

Following is a brief overview of the different types of laser eye surgery that use surface ablation techniques:

PRK (PhotoRefractive Keratectomy) In PRK the outermost layer of the cornea (epithelium) is manually scraped away and an excimer laser reshapes tissues located on the underlying (stromal) surface of the cornea. Afterwards the epithelium layer must grow back. PRK is an option for those with thin corneas where the creation of a cornea flap by cutting is undesirable. Drawbacks of PRK include a longer recovery period and more discomfort during healing than with LASIK. The two main advantages are that PRK does not create a cornea flap by microkeratome blade, which is the part of laser eye surgery that carries the most risk, and it does not penetrate deeply into the cornea, reducing the risk of ectasia. (Ectasia is a condition of inner eye pressure pushing out against a thinned corneal wall, causing it to bulge resulting in worsening vision over time.)
A Canadian version of PRK (transepithelial PRK) uses an excimer laser to vaporize the epithelium, rather than manually scraping it away.
LASEK (Laser Assisted Sub-Epithelial Keratomileusis), An advanced form of PRK that uses alcohol in solution to first soften then remove the epithelium. After the excimer laser reshapes the stroma to correct the vision, the epithelium is replaced. The advantage of LASEK over PRK is that the healing process is hastened while still avoiding the use of a cutting blade to create a cornea flap.

Epi-LASEK This modified LASEK procedure uses a “separator” to preserve a living layer of epithelium, which is replaced after the excimer laser reshapes the stroma. Epi-LASEK seeks to reduce discomfort and healing time even further than LASEK.

Following are examples of LASIK, or the different types of laser eye surgery that create a corneal flap by cutting, either with a microkeratome blade or laser:
LASIK (Laser-Assisted In Situ Keratomileusis) uses a microkeratome metal blade to cut the cornea flap and an excimer laser to reshape the eye. After the procedure, the flap is returned to its position. This is painless for most patients, and unlike PRK techniques, vision is immediately corrected, though some blurriness may be present for the first 24 hours and vision will improve for a period of weeks.

Custom Vue Lasik: Uses the same hardware as conventional Lasik but the excimer laser is guided by advanced software called Wavefront. In this procedure vision is measured by mapping the optical system using technology that is 25% more accurate than traditional methods. The map is so exact it is likened to a fingerprint. No two surgeries are alike, hence the name. Because of the precision it can be used to correct vision or to correct imperfections created by other laser procedures. Reportedly patients can expect 20/20 vision using Custom Vue Lasik with many people experiencing even better results. The need for a second procedure is less common (but if the microkeratome blade causes imperfections during the Custom Vue session, those imperfections would not be correctable until a later procedure).

Conventional IntraLasik Uses a femtosecond Intralase laser to make the corneal flap, rather than a metal blade. This allows a much thinner flap to be created, and eliminates imperfections caused by a metal blade. This is regarded as a far superior method for corneal flap creation. The only drawbacks are that it takes about a minute to create a flap, rather than seconds, and it is more expensive. Also, if an excimer laser is used without Wavefront technology, imperfections can still result from the second step of the procedure — the actual reshaping of the eye.

Custom Vue IntraLasik This type of laser eye surgery combines the best of all worlds. It uses a laser to create a cornea flap, and Custom Vue’s Waterfront technology to guide the excimer laser for the best possible results. It is also the most expensive type of laser eye surgery.

Custom Vue with Wavefront guidance technology cannot be used with all excimer lasers. VISX Star S4 is one type of laser that does accommodate it, and it is a “tissue saving” model as well. Other types of excimer lasers are guided by other wavefront technologies. Some require the pupils be dilated for the mapping process, such as the Alcon LADARVision laser that uses CustomCornea Wavefront technology. Some physicians report that dilation can cause the center of the pupil to shift, offsetting the preciseness of the wavefront map, resulting in less than optimal results. In FDA clinical trials where nearsighted patients underwent laser surgery and were retested after a 6-month period, 95.8% of those who were treated with VISX Star4 Custom Vue Lasik retained 20/20 vision, compared to 79.9% treated by Alcon LADARVision CustomCornea.

There are many issues associated with laser eye surgery and this article is not intended to be an exhaustive list of those issues nor an endorsement of any particular brand or technology, but rather a guide so that you will be more prepared to ask questions of your ophthalmologist about any options he or she may present. Among the questions you might want to ask: What is the baseline of expectation associated with this type of laser eye surgery? How accurate is the mapping/reshaping process? What percentage of people require a second procedure? What percentage of people have halo, glare, or night vision problems afterwards? Is the laser and procedure 100% FDA-approved?
Most reputable centers for eye laser surgery note that 20/20 vision from laser-corrected surgery may not be like 20/20 vision with corrective lenses. Some haze or other side effects can result from laser eye surgery, though technology is always working to eliminate these. The most advanced techniques that carry the least amount of risk for side-effects are often more expensive. RK (Radial Keratotomy) is an obsolete form of corrective eye surgery that reshaped the cornea by making a series of radial slits. RK predates the excimer laser and people who had RK may benefit from PRK or Lasik.