What does LASIK eye surgery involve?

There are several variations of laser refractive surgery. LASIK is the best known and most commonly performed. Many articles, including this one, will use the term “LASIK” to refer to all types of laser eye surgery.

Normally, images are focused on the retina in the back of your eye. With nearsightedness (myopia), farsightedness (hyperopia) or astigmatism, they end up being focused elsewhere, resulting in blurred vision.

Myopia (shortsightedness) is a condition in which you see nearby objects clearly, but distant objects are blurry. When your eyeball is slightly longer than normal or when the cornea curves too sharply, light rays focus in front of the retina and blur distant vision. You can see objects that are close more clearly, but not those that are far away.
Hyperopia (farsightedness) is a condition in which you can see far objects clearly, but nearby objects are blurry. When you have a shorter than average eyeball or a cornea that is too flat, light focuses behind the retina instead of on it. This blurs near vision and sometimes distant vision.
Astigmatism causes overall blurry vision. When the cornea curves or flattens unevenly, the result is astigmatism, which disrupts focus of near and distant vision. Traditionally, blurry vision is corrected by bending (refracting) light rays with glasses or contact lenses. Reshaping the cornea will also provide the necessary refraction and vision correction.

Before a LASIK procedure your eye surgeon will assess detailed measurements of your eye (including eye biometry and corneal topography examination). Then a surgeon will use a special type of cutting laser (excimer laser) to precisely reshape the curvature of your cornea. With each pulse of the laser beam, a tiny amount of corneal tissue is removed, allowing your eye surgeon to flatten the curve of your cornea or make it steeper.

Most commonly, the surgeon creates a flap in the cornea (FEMTO LASIK or LASIK procedure), and then raises it up before reshaping the cornea. There are also variations in which a very thin flap is created (epi-LASIK procedure) or no flap at all (PRK procedure). Each technique has advantages and disadvantages.

Individual eye surgeons may specialize in specific types of laser eye procedures. The differences among them are generally minor and none are clearly better than any others.

Depending on your individual circumstances and preferences you may consider:

FEMTO LASIK (ALL LASER LASIK – femtosecond LASIK) – the femtosecond laser creates a corneal incision by delivering laser pulses at a predetermined depth in the cornea. These pulses cause microphotodisruption, an expanding bubble of gas (CO2) and water that cleave the tissue and create a plane of separation. Compared to conventional mechanical microkeratomes, femtosecond lasers create LASIK flaps with more predictable and uniform thickness, and fewer complications. However, side effects unique to the femtosecond laser, such as transient light sensitivity syndrome, have been reported. Femtosecond laser aided LASIK has been shown to provide better predictability of refractive outcomes and lower enhancement rates than LASIK performed using a microkeratome, epi-LASIK, PRK and LASEK.

Photorefractive keratectomy (PRK) – with PRK, the top surface (corneal epithelium the upper surface of the cornea) is scraped or removed using concentrated alcohol. This corneal abrasion takes three or four days to heal, resulting in moderate pain and blurred vision in the short term. It was thought that these drawbacks were outweighed by the theoretical advantage that PRK was safer for people who are more likely to be struck in the eye — for example, those involved in contact sports, law enforcement forces and / or the military. But even with standard LASIK, the risk of eyeball rupture is still very low, so there is probably no significant advantage with PRK. LASIK, due to the need to create a flap of the outer layer of the cornea, is also theoretically a worse surgical method than PRK in the case of correction of high shortsightedness.

Laser-assisted subepithelial keratectomy (LASEK) – LASEK is similar to LASIK surgery, but the flap is created by using a special cutting device (microkeratome) and exposing the cornea to ethanol. The procedure allows the surgeon to remove less of the cornea, making it a good option for people who have thin corneas. For people at greater risk of eye injuries, LASEK does not have any significant advantages over LASIK.

Epithelial laser-assisted in-situ keratomileusis (epi-LASIK) – in an epi-LASIK procedure, your surgeon separates the epithelium from the middle part of the cornea (stroma) using a mechanized blunt blade device (epikeratome) and reshapes the cornea with a laser. This procedure is similar to LASEK.

Implantable lenses – corrective lenses can be surgically inserted in the eye to improve vision. This is routinely done as part of cataract surgery (in which the old, cloudy natural lens is removed). It may also be an alternative to LASIK for older adults who may need cataract surgery in the future. Younger people with high degrees of nearsightedness that cannot be satisfactorily treated with corrective lenses may also be offered implantable lenses. But this is not a routine option for most people.

Bioptics combines – one or more techniques, such as implantable lenses and LASIK, to treat nearsightedness or farsightedness. Again, this is not an option for most people seeking refractive eye surgery.