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Laser eye surgery terminology – do you know your LASIK from your keratectomy from your lenticule?


Laser eye surgery terminology – do you know your LASIK from your keratectomy from your lenticule?

As laser eye surgery is a medical procedure, patients may hear a lot of unfamiliar words. That’s why we’ve put together this handy guide.


In surgery, to ablate is to remove (see ASLA).

ASLA (advanced surface laser ablation) or PRK (photorefractive keratectomy)

ASLA or PRK was the first laser eye surgery option introduced and is still in use today. The procedure involves removing the epithelial layer (the top layer of the cornea). This layer naturally regenerates after surgery.

Once the layer is removed, the excimer laser is used to reshape the underlying corneal tissue.

Correcting short-sightedness (myopia) entails removing tissue in the middle to create a flatter surface. Correcting long-sightedness (hyperopia) requires removing tissue from the corneal edges. Excimer lasers correct astigmatism by reducing corneal irregularity and providing a more even surface for improved light refraction.


A deviation of a spherical curve (the cornea) resulting in distorted images. In classic Greek, the ‘a’ is ‘without’, while the ‘stigmata/stigmat’ refers to a point – so it is literally ‘without point’.

Astigmatism is a common refractive error that can be corrected with laser eye surgery.

Epithelial layer

The cornea consists of five layers, and the top layer is called the epithelial layer. Laser eye surgery involves the epithelial layer (the epithelium) and the stromal layer (the stroma).

Excimer laser

An excimer laser uses gas to produce energy through which the cornea can be permanently reshaped without the need for any heat. No burning occurs.

Femtosecond laser

A femtosecond laser is used in LASIK laser eye surgery to create a flap of tissue which can be lifted and replaced back into its original position. The word ‘femtosecond’ relates to the amount of time it takes for a single pulse – a ‘femtosecond’ converts to approximately one quadrillionth of a second.

The purpose of the femtosecond laser is to create the ‘flap’ in LASIK laser eye surgery.


In Greek, ‘hyper’ means ‘beyond’ and ‘ops’ means ‘eye’. Hyperopia refractive error refers to ‘overcorrect/over measure’. You may know hyperopia as long-sightedness or far-sightedness.

Laser eye surgery can be used to correct hyperopia.


Refers to the surgical removal of a layer of the cornea.


Keratomileusis refers to the reshaping of the cornea in order to correct a refractive error – ‘kerato’ relating to the cornea, and ‘mileusis’ a reference to the Greek term for ‘carving’. Granted, this is not the most elegant description of laser vision correction.

LASIK – laser in-situ keratomileusis

The term LASIK refers to laser-assisted in-situ keratomileusis. This type of laser eye surgery differs from ASLA (or PRK) in the way a surgeon accesses the cornea. Instead of removing the entire epithelial layer, process requires creating a flap.

With the flap open, a surgeon alters the corneal tissue. With the procedure completed, the flap is closed. As the eye does not have to recreate the entire epithelial layer, recovery time is much faster.


‘Lenticular’ refers to something that is curved on both sides. Lenticule is the term for a ‘disc-shaped piece of corneal tissue’. A precise measurement is created, as determined by the individual’s refractive error – when it is removed, the curvature of the cornea is reshaped and vision is corrected.


In Greek, ‘ops’ refers to ‘eye/look‘, ‘myein’ to ‘shut’. Myopia literally means ‘trying to see like a mole’. You may know ‘myopia’ better as short-sightedness or near-sightedness. Laser eye surgery can correct myopia.


Refractive refers to the measurement of the focusing characteristics of the eye. A refractive error is created when the light focusing through the cornea and lens does not focus clearly on the retina. This can be due to an incorrect eye length, or incorrect power or curvature of the cornea or lens.

SMILE® – small incision lenticule extraction

The term SMILE refers to small incision lenticule extraction. This form of laser vision correction does not require the surgeon to create a corneal flap. Instead, the procedure entails making a tiny keyhole incision to remove the lenticule created by the femtosecond laser.

The SMILE technique may offer a solution for patients suffering from chronic dry eyes or for individuals diagnosed with having a thin cornea.


The layer of the cornea that sits under the superficial epithelial layer. This is the layer that requires reshaping during laser eye surgery in order to correct vision.

Find out more about laser eye surgery

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The information on this page is general in nature. All medical and surgical procedures have potential benefits and risks. Consult your ophthalmologist for specific medical advice.

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