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The Laser Eye Surgery Dictionary

There are lots of different and sometimes confusing terms used when describing laser eye surgery procedures. If you're looking for answers, you'll find them here.
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Each title and/or + sign is clickable, expanding the definition. Learn more laser eye surgery acronyms and technical terms here. Open one, automatically close another.
20/20

20/20 describes a way of measuring your level of vision (acuity). 20/20 means that you are able to see the same detail from 20 feet away as an average person from the same distance (20 feet). The equivalent test result in meters is 6/6. If your vision is better than this level, the denominator reduces, e.g. 20/16 or 6/5.

Ablation

Ablation is the removal of corneal tissue with an excimer laser. LASIK, LASEK, PRK and TransPRK use excimer lasers to reshape the cornea to improve vision without spectacles. Daniel Gore uses the Schwind Amaris 1050RS, the fastest excimer laser on the market with 7-dimensional tracking of your eye up to 1050 times a second. A typical ablation for LASIK takes less than 10 seconds. A LASEK or TransPRK ablation through the outermost layer of the eye (epithelium) takes about 30 seconds.

Accommodation

Accommodationis the ability of the natural lens inside the eye to change its focus to see both far and near. Accommodation decreases with age because the lens gradually loses its flexibility. At this point, you’ll start to need reading glasses to see your phone or read a newspaper.

Acuity

The sharpness of vision. See 20/20 above.

Astigmatism

Astigmatism is a common refractive or ‘focusing’ error. A common analogy used is that of a rugby ball vs. a football. If you have no astigmatism, your cornea (clear window at the front of the eye) is completely spherical (i.e. perfectly round like a football). If you have astigmatism, the cornea is slightly steeper along one axis (rugby ball). Most people have some degree of astigmatism, which often changes with increasing age. Astigmatism can cause blurred vision forboth reading and distance by projecting light in two different places in the eye.It can be corrected with contact lenses, spectacles and laser eye surgery.

Bandage Contact Lens

A soft contact lens withlittle or no refractive power that is placed on the eye to improve healing after laser eye surgery. The lens stays in overnight for LASIK; Daniel Gore removes this lens from your eye the following day. For LASEK or TransPRK treatments, the bandage lens stays in for up to a week.

Bilateral

Bilateral surgery describes having both eyes operated on the same day. It is standard practice to have bilateral laser eye surgery. Cataract surgery is typically performed one eye at a time (unilateral).

Cornea

The clear window at the front of the eye that focuses light rays through the pupil. Two-thirds of the eye’s refractive power comes from the cornea.One-third comes from the lens. To get outstanding results from your laser eye surgery, make sure your surgeon has sub-specialty corneal training. Daniel Gore completed three years fellowship training at Moorfields Eye Hospital in advanced corneal disease.

Cross-linking (CXL)

Corneal cross-linking (CXL) is the only treatment available to halt disease progression in keratoconus. It is effective in over 90% of treated eyes. Combined with laser eye surgery, it can also help to improve vision.  CXL is performed by exposing riboflavin-soaked corneal tissue to an ultraviolet light source, together generating ‘cross-links’ within the cornea to strengthen it.

Mr Gore leads the Corneal Cross-Linking Service at Moorfields Eye Hospital and is an expert on keratoconus.

Dioptre

A unit to quantify refractive power of spectacles or your eye.It is usually abbreviated to the letter ‘D.’ Diopters are used to describe the level of visual error, where 0Ddescribes no refractive error. Minus numbers (e.g. -6.00 D) denote short-sightedness (myopia). Plus numbers (e.g. +2.50) denote long-sightedness (hyperopia).

Diplopia

Seeing "double", or when you see two distinct images of one object when you should see one. Not to be confused with blurred vision / shadowing.

Dry Eye Syndrome

A condition in which your eyes don’t produce enough tears, or that your tears evaporate too quickly. Dry eye can cause discomfort and blurry vision. It is common earlyon after laser eye surgery, typically subsiding over several weeks and months. During an initial consultation with Daniel Gore, he will advise you if your eyes are dry and whether treatment is required before your laser eye surgery. Some patients with dry eyes are not suitable for laser eye surgery. In these cases, implantable contact lenses (ICL) may be a safer option.

Emmetropia

The medical term when there is no refractive error with the eye in a relaxed state and without effort (no accommodation). The eye focuses distant images onto the retina with a single focal point (i.e. no need to wear glasses for distant vision).

Epithelium

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

Excimer Laser

An ultraviolet laser used in laser eye surgery to remove corneal tissue by ablation. 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

A femtosecond laser is very short-pulsed, near infrared laser used in LASIK and SMILE surgery. The short pulse duration creates extreme precision ‘cuts’ in the corneal stroma without damaging adjacent tissue.

Flap

A LASIK flap is a thin, hinged layer of corneal tissue created by a femtosecond laser, under which an excimer laser ablates tissue to reshape the cornea. After the ablation, the flap is laid flat.

Haloes

Rings around point light sources (e.g. street lights or car headlights). Haloes were a common complaint in the early years of laser vision correction. This was often because laser corrections on the cornea were smaller than patient’s night-time pupil size. As laser technology has improved it has allowed larger diameter treatments, with transition zones extending beyond the edge of the pupil. Your pupil size will be measured during your initial consultation.

Hyperopia

The medical term for long-sightedness, describing a condition in which there is not enough power in the eye to focus light rays onto the retina. The closer the object, the more blurry your vision. Contact lenses, spectacles or laser eye surgery can correct hyperopia.

Keratoconus

Keratoconus is a progressive condition in which the corneal shape becomes steeper and more irregular causing blurred vision. The gold-standard treatment for progressive keratoconus is corneal cross-linking.

Keratectomy

Refers to the surgical removal of a layer of the cornea, usually with a laser. 

LASEK

The acronym stands for Laser Sub-Epithelial Keratomileusis.

LASEK & TransPRK eye surgeries are both examples of laser treatments applied directly to the surface of the cornea (without a flap). LASEK involves manually brushing away the corneal skin layer (epithelium). A more advanced technique, transepithelial photorefractive keratectomy (TransPRK), reshapes the cornea through the epithelium. TransPRK with the Schwind Amaris 1050RS laser using SmartSurfACE technology, is a 'no-touch' technique - applying the laser light directly to the surface of the eye means no brushing, no cutting and no flap.

LASIK

The acronym stands for Laser In Situ Keratomileisis.

In LASIK eye surgery, a femtosecond laser – which emits ultra-fast pulses of light allowing for extreme precision– is used to ‘cut’ a thin flap of corneal tissue, underneath which an excimer laser – ultraviolet light – is applied. The flap is then laid flat at the end of the procedure. 

Long-sighted

See Hyperopia (above)

Monovision

Monovision describes correcting the focusing for one eye for distance vision and the other eye for reading vision. With both eyes open, the brain receives a spread of focus which can help reduce dependence on reading glasses (presbyopia). Monovision can be used in contact lenses and works very well in laser eye surgery for patients already dependent on reading glasses.

Myopia

The medical term for short-sightedness, describing a condition in which there is too much power in the eye, focusing light in front of the retina. Contact lenses, spectacles or laser eye surgery can correct myopia.

Overcorrection

Overcorrection describes a refractive error remaining after laser eye surgery. This may occur due to differences in how the eye heals after surgery or too much tissue being ablated during the procedure. If still present after the healing process is completed, repeat laser eye surgery (enhancement) may be considered to fine tune the vision result. To give you piece of mind, Daniel Gore offers enhancements, if required, free of charge for 2 years from the time of surgery.

Presbyopia

A condition in which the eye’s natural lens loses its flexibility, causing impaired ability to see close objects sharply. Presbyopia typically develops in you 40s and eventually requires the use of reading glasses. Laser eye surgery can treat presbyopia.

Stroma

The layer of the cornea under the superficial (outermost) epithelial layer. The stroma is reshaped with an excimer laser to correct vision.

TransPRK

The acronym stands for transepithelial photorefractive keratectomy.

LASEK & TransPRK eye surgeries are both examples of laser treatments applied directly to the surface of the cornea (without a flap). LASEK involves manually brushing away the corneal skin layer (epithelium). A more advanced technique, transepithelial photorefractive keratectomy (TransPRK), reshapes the cornea through the epithelium. TransPRK with the Schwind Amaris 1050RS laser using SmartSurfACE technology, is a 'no-touch' technique - applying the laser light directly to the surface of the eye means no brushing, no cutting and no flap.

Undercorrection

Undercorrection describes a residual refractive error remaining after surgery. This occurs due to differences in how a person's eyes heal after surgery. If still present after the healing process is completed, repeat laser eye surgery (enhancement) may be considered to fine tune the vision result. To give you piece of mind, Daniel Gore offers enhancements, if required, free of charge for 2 years from the time of surgery.

Visual Acuity

A measurement of vision. 

20/20 describes a way of measuring your level of vision (acuity). 20/20 means that you are able to see the same detail from 20 feet away as an average person from the same distance (20 feet). The equivalent test result in meters is 6/6. If your vision is better than this level, the denominator reduces, e.g. 20/16 or 6/5.


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