Refractive error correction methods (Part 2)

1399/10/16 - 17:49 / 32

What is LASIK eye surgery?

 

LASIK stands for Laser in Situ Keratomileusis, which means using a laser underneath a corneal flap (in situ) to reshape the cornea (keratomileusis). This procedure utilizes a highly specialized laser (excimer laser) designed to treat refractive errors, improve vision, and reduce or eliminate the need for glasses or contact lenses. This laser procedure alters the shape of the cornea, which is the transparent front covering of the eye. Though the excimer laser had been used for many years before, the development of LASIK is generally credited to Ioannis Pallikaris from Greece around 1991.

 

How does LASIK work?

 

During the LASIK procedure, a specially trained eye surgeon first creates a precise, thin hinged corneal flap using a microkeratome. The surgeon then pulls back the flap to expose the underlying corneal tissue, and then the excimer laser ablates (reshapes) the cornea in a unique pre-specified pattern for each patient. The flap is then gently repositioned onto the underlying cornea without sutures.

 

 

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How do glasses or contacts improve vision in people with refractive errors?

 

Glasses or contact lenses are used to compensate for the eye's refractive error by bending light rays in a way that complements the eye's specific refractive error. In contrast, LASIK and other forms of refractive surgery are intended to correct the eye's refractive error to reduce the need for other visual aids.

 

Will You Still Need to Wear Glasses or Contacts After LASIK?

 

Laser vision correction is designed to reduce or eliminate your need for glasses and contact lenses. Although many patients are able to function well without any glasses or contact lenses, some still require optical correction for certain tasks. In addition, laser vision correction does not change the condition known as presbyopia, which is the expected difficulty with close work as one reaches the age of 40 or older. Monovision laser procedures, which involve having one eye corrected for distance and the other for seeing up close, are an option to reduce the effects of presbyopia.

LASIK cannot directly "fix" accommodation, but there are a variety of strategies that can be successful, including blended vision or monovision, in which one eye is corrected for better distance vision and one eye is corrected for better near vision.

 

What are the risks of LASIK?

 

LASIK has been shown to be a very effective procedure, and most patients are very happy with their vision following the procedure. However, like any surgical procedure, LASIK does come with some risks. In order for you to decide whether LASIK surgery is right for you, you need to be aware of potential risks and complications and weigh these carefully before proceeding with surgery.

You may be over-corrected or under-corrected. Most patients are satisfied with their vision after a single treatment, but in some cases, you may not achieve quality vision initially and need a second surgery, called an enhancement, to sharpen your vision. Patients with more extreme prescriptions are at higher risk for needing an enhancement. This enhancement cannot be performed for many months after your initial surgery to allow for your eyes to heal appropriately from the first surgery and for your eyeglass prescription to stabilize. In some rare cases, you may not be able to have an enhancement if your corneas are too thin or abnormally shaped after surgery.

You may still need glasses or contact lenses after surgery to achieve your best vision. This is extremely rare for the average person; however, it is something you should discuss with your surgeon. In addition, if both of your eyes are corrected for good distance vision, you will still need glasses for close work when presbyopia develops as a part of normal aging process.

 

 

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Your results may not be permanent. Although uncommon, some patients do experience a regression of their desired treatment effect many years after the surgery. This is more common in patients with hyperopia, or farsightedness. Those who need reading glasses are especially prone to having changes in their vision after LASIK surgery. If regression does occur, it may be possible for you to have an additional surgery many years after your initial LASIK.

You may experience visual aberrations, especially in low light. Visual effects that can occur with LASIK and decrease visual quality include: anisometropia (difference in refractive power between the two eyes), aniseikonia (difference in image size between the two eyes), double vision, hazy vision, fluctuating vision during the day and from day to day, increased sensitivity to light, glare, shadows, and seeing halos around lights. These visual aberrations are extremely unusual; however, they may be incapacitating for some time and may not ever go away completely.

Dry eye symptoms may persist or get worse. Most people experience some dry-eye symptoms immediately after surgery. In some cases, people may develop worsening of dry-eye symptoms, such as burning and redness, or even decreased vision, after surgery. This condition is occasionally permanent and may require medication to improve tear production or punctal plugs, which temporarily close off the drainage system for tears.

You may lose vision. Rarely, LASIK may result in worse vision that cannot be corrected with glasses or contact lenses. This could result from flap-related complications, equipment malfunction, infection, scarring, or extreme changes in corneal shape postoperatively.

 

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What should I expect after surgery?

 

As soon as the procedure is finished, you may notice that your eyes feel irritated, burn,itch  or feel like there is something in them. Your eyes will frequently water or tear excessively, and your vision will be somewhat blurry. The most important thing to avoid during this time is rubbing your eyes. Do not rub your eyes under any circumstances, as rubbing can dislocate or shift the corneal flap, which could require you to have an additional procedure to reposition it. Using copious artificial tears and resting with your eyes closed will most effectively ease these sensations. In some instances, there may be increased discomfort or even a mild degree of pain, for which your doctor may advise you to take a pain reliever . In most cases, nonsteroidal anti-inflammatory drugs , such as ibuprofen, are enough to relieve the pain. In addition to artificial tears, you will have antibiotic drops and anti-inflammatory drops (steroids) to use beginning on the day of surgery that you will continue to use for days to weeks after surgery.

Other symptoms you may notice immediately after surgery include light sensitivity, hazy vision, glare, seeing starbursts or halos around lights, and reddened or bloodshot eyes. All of these symptoms should improve over the first few days following surgery. It is very important that you contact your doctor immediately on the first night after surgery if you are having severe pain or if your vision is getting worse and not better. You do not need to wait until your first follow-up visit if you are experiencing either of these things.

Your first postoperative visit should be scheduled within the first 24 hours following surgery. At that visit, your doctor will check your vision and examine your eyes. You will continue to use your antibiotics and steroid drops as well as artificial tears. Your vision should be clearer but may still be blurry the first few days after surgery, and you may need to adjust your work or travel schedule or even take some time off after surgery to fully recuperate.

You should ask your doctor how long you need to wait to start participating in sports again, such as walking or jogging. In general, you should wait anywhere from one to three days following surgery to restart low impact sports, and avoid any possible eye trauma, such as more competitive sports, for a minimum of 2 or more weeks. In addition, it is unwise to expose yourself to eye infection risks such as pools, lakes, or hot tubs during the early healing process. Your surgeon will tell you when you can resume these activities.

As mentioned earlier, lotions, creams, makeup, and perfumes can often cause buildup on the eyelids and may increase the risk for infection. Ask your doctor when it is advisable to resume use of these products.

Typically, your vision will stabilize within the first week or two, but it may continue to change over the first couple of months following surgery. It may take anywhere from 3-6 months for your vision to stabilize completely. Other visual symptoms, such as glare, seeing halos, and difficulty driving at night, may continue during this stabilization period. Additional treatments, or enhancements, may be needed after surgery, but the stability of your cornea will need to be established before any repeat treatments are performed. Before enhancements are considered, you should have had consistent eye measurements at two consecutive visits. When considering additional treatments, you should know that while it is likely that your vision can be improved by enhancements, just as with the initial surgery, there are no guarantees, and there are still risks associated with having surgery.

You should not hesitate to call your eye doctor immediately if you develop worsening or unusual symptoms at any time after surgery. These symptoms could be a sign of a serious problem that could result in loss of vision if not treated properly in a timely fashion.

 

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Prepared:
Neshat Khosravi - Microbiologist

Reference:

https://www.medicinenet.com



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