How Does LASIK Eye Surgery Correct Vision?

If you’ve been putting up with glasses or contact lenses for any number of years, the thought of LASIK eye surgery may have crossed your mind once or twice. However, the eyes are delicate and sensitive organs and you want to be sure LASIK surgery is the right thing for you and your vision. If you’re wondering how LASIK eye surgery corrects vision and is it for you, keep reading. 

A Word on Refractive Error

Before explaining how LASIK eye surgery corrects vision, it helps to understand a bit more about the presenting problem – refractive error. 

Refractive error describes the failure of the eye to focus incoming light sharply onto the retina, which is what we need in order to see clearly. You may know refractive error as your prescription, such as -1.00 dioptres (D) or +2.50D. Refractive errors encompass:

• Myopia. Also called short or nearsightedness, myopia typically occurs because the length of the eyeball is too long for its focusing power. This results in light coming to a focal point in front of the retina, rather than on it. Myopic patients will find their long-distance vision is blurry, while their near vision is okay.
• Hyperopia. Hyperopia is also known as far or long-sightedness. In a sense, it is the opposite of myopia in that the length of the eyeball is considered too short for its focusing power, such that the focal point falls behind the retina. However, rather than hyperopic patients being able to see far away but not up close, many long-sighted people can see all distances clearly, particularly when they’re young. 
• Astigmatism. Astigmatism occurs when one or more refractive surfaces in the eye is not uniform, causing light to bend to different degrees depending on the angle it enters the eye. Most instances of astigmatism occur from an uneven curvature of the cornea, the front surface of the eye. However, a smaller percentage of astigmatism may arise from the lens inside the eye being an uneven shape. 

The premise underlying the correction of any sort of refractive error is modifying how light bends through the eye. Non-surgical means of this involve glasses and contact lenses, which redirect the passage of light as it enters the eye so that its rays come to a sharp focal point right on the retina. This is how we perceive sharp vision. 

However, for those who are deliberately trying to get away from glasses and contacts, LASIK eye surgery is probably an attractive option. So, how does LASIK eye surgery correct vision? 

How Does LASIK Eye Surgery Correct Vision?

LASIK surgery, and all other laser eye surgery procedures, are built on the concept of changing the shape of the cornea. The cornea and the tear film that overlies it is the first refractive surface that light passes through as it enters the eye. By surgically adjusting the curvature of the cornea, the refraction of light is altered such that it comes to a sharp point on the retina, thereby allowing clear sight. 

It’s important to understand that LASIK surgery is not able to correct or restore any vision loss that is not due to refractive error.

If your eyesight is limited due to diseases, such as a retinal detachment, macular degeneration, or amblyopia (lazy eye), LASIK eye surgery will not be able to improve your vision any further than can be achieved with glasses or contacts. 

LASIK surgery tends to be used only to correct long distance sight. This means if you’re experiencing the natural age-related decline in your near focusing ability, known as presbyopia, it may not be worth having LASIK. Instead, your surgeon may offer you a different refractive surgery technique, such as implantable Collamer lenses (ICL). Alternatively, if you are deemed an eligible candidate, you may opt to undergo Presbyond, which is a modified LASIK eye surgery technique. During Presbyond LASIK surgery, your cornea is reshaped in a way that allows areas of both distance and near vision in the same eye. This allows you a degree of functional vision at all focusing distances. 

The Steps of LASIK Eye Surgery

LASIK surgery is a fairly straightforward procedure with high success rates. Each eye only takes about 10 to 15 minutes for the operation, with your sight improving in as little as a day. 

To prepare you for LASIK eye surgery, your eye will be numbed with topical anaesthetic eyedrops. As you lie on the operating bed, you’ll be given an overhead target to fixate on for the duration of your LASIK surgery. 

LASIK eye surgery is defined by the creation of a circular flap of superficial corneal tissue. The flap can be made either using a handheld bladed tool called a microkeratome or with a femtosecond laser. It’s then moved to the side of the eye while remaining attached at a hinge. 

Once the deeper stromal layers of the cornea have been exposed, an excimer laser is then used to selectively vaporise sections of tissue. This process is guided by a computer algorithm to ensure the cornea is reshaped in a highly precise manner. 

After the vaporisation is complete, the corneal flap is replaced and allowed to self-seal. You’ll be given a protective eye shield, some medicated eye drops, and a list of post-operative instructions for the recovery period. 

If you’re interested in LASIK surgery, speak to your optometrist or ophthalmologist about whether you’re a suitable candidate. If LASIK is not considered appropriate for you, there may be other options to surgically correct your vision. 

Note: Any surgical or invasive procedure carries risks. Before proceeding, you should seek a second opinion from an appropriately qualified health practitioner.

References

LASIK procedure: A guide for what to expect.

https://www.allaboutvision.com/en-au/vision-surgery/lasik/

LASIK eye surgery.

https://www.mayoclinic.org/tests-procedures/lasik-eye-surgery/about/pac-20384774