Page 71 - The UK Guide to Laser Eye Surgery
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 Glossary
71
D
Decentration
A potential complication of laser eye surgery. In perfect centration, the centre of the corneal ablation exactly coincides with the centre of the visual axis. This allows for sharp, focused vision – like looking through the very centre of your spectacle lens. If the area of your cornea treated by the laser is off to one side, this is known as decentration (or ‘off-centred ablation’). Decentration can cause various symptoms, including edge glare or even monocular double vision. Other factors, such as the size of the pupil, the amount of light in your surroundings, and the size of the ablation zone will affect the severity or presence of symptoms.
Dilation
The process by which the pupil enlarges, usually in low light conditions. Alternatively dilation can be induced artificially by special eye drops, which is necessary to examine the health of the back of the eye.
Dry eye
The term ‘dry eye’ is used to describe a variety of disorders with similar symptoms: discomfort, a feeling of dryness, burning or stinging, grittiness, foreign body sensation and photophobia.
E
Ectasia
An outward bulging and thinning of the cornea due to raised internal eye pressure and/or a weakened cornea.
Endothelium
The inner layer of cells on the inside surface of the cornea.
Enhancement
A secondary laser eye surgery treatment or retreatment, performed to refine or improve the original visual result.
Epi-LASIK
See Laser Assisted Epithelial Keratomileusis.
Epithelial ingrowth
A potential complication of LASIK, in which epithelial cells under the corneal flap begin to grow and multiply. The most common treatment is lifting the corneal flap, removing the cells, irrigating the interface and repositioning the flap. Most cases,
if managed appropriately, have a good outcome.
Epithelium
The outer surface layer of the cornea – the skin.
Excimer laser
An argon-fluoride laser that emits ultraviolet light in pulses, at a wavelength of 193nm. The term excimer comes from the concept of ‘an energized molecule with two identical components’. Each pulse
of this cool laser removes 1/4000th of
a millimetre of tissue from the targeted surface, by breaking the bonds between the molecules of collagen. It would take about 200 pulses from an excimer laser to cut a human hair in half.
Continued on the next page
Dioptre (D)
A unit of measurement of the refractive power of a lens.
Double vision
Also called ‘ghosting’, this means seeing double images. For example, looking at a clock and finding that some of the numbers appear to have a lighter image repeated next to them.



































































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