Page 72 - The UK Guide to Laser Eye Surgery
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 72 Glossary
FHK
Far-sightedness
See ‘Hyperopia’.
Femtosecond laser
A femtosecond laser is a laser that emits optical pulses with a duration of 1/4000th of a second. Femtosecond laser technology is used for the SMILE laser eye surgery procedure, and to create a corneal flap in LASIK.
Focusing power
The cornea is responsible for about two- thirds of the focusing power of the eye. As light enters the eye, it is focused by the cornea. Then, as the light passes through the pupil, the lens adjusts the focus, depending on the distance of the object being viewed. Close objects, such as a book or computer screen, require more power than distant objects, such as traffic signs.
G
Ghosting
See ‘Double vision’.
Halos
Images from light sources look blurred with circles radiating outward from the centre. Halos can appear as a complication of refractive surgery but they also occur naturally.
Hyperopia
Also known as far-sightedness or long- sightedness. Hyperopia occurs when the eyeball is too short from front to back or the focusing mechanism is too weak. This causes light rays to be focused behind, rather than on, the retina. People with hyperopia have difficulty seeing objects that are close by.
I
Intraocular
Inside the eye.
Intraocular lens (IOL)
Silicone, acrylic or plastic lens used to replace the natural crystalline lens of the eye. See also ‘Clear Lens Exchange’.
Intraocular pressure (IOP)
Pressure inside the eye.
J
Joules
Joules is the unit measurement of energy.
Keratectomy
Surgical removal of corneal tissue.
Keratoconus
A disorder that causes thinning and asymmetry of the cornea. The normally symmetrical shape of the cornea becomes distorted. A cone-shaped bulge develops, and this can result in significant visual impairment.
Keratomileusis
A refractive surgical technique in which a thin, circular flap of the cornea is removed, frozen, reshaped on a lathe and replaced upon the cornea.
L
Laser
LASER stands for Light Amplification by the Stimulated Emission of Radiation. Laser light is composed of one colour (wavelength), travelling in one direction, and each light wave is in step with the next. This makes laser light millions
of times more powerful than ordinary daylight.
Laser in-situ keratomileusis (LASIK)
A surgical procedure to reshape the central cornea, decreasing or eliminating myopia, hyperopia, and astigmatism. The surgeon creates a flap in the cornea, and the exposed eye surface below is reshaped using an excimer laser. After altering the corneal curvature, the flap is replaced. It adheres quickly, without stitches.
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