Ametropia
Eye disorders that prevent a clear image from forming on the retina, with the exception of age-related presbyopia. Myopia, hyperopia and astigmatism are all forms of ametropia.
Astigmatism
An irregular cornea shape prevents light rays to be focused to one point so that objects appear blurred or distorted. Eye glasses and toric contact lenses or refractive surgery can correct astigmatism.
Cornea
The outer, transparent part of the eye's focusing system that covers the eye's iris, and anterior chamber. It transmits and focuses light into the eye and provides most of the eye's refractive power. The cornea can be considered to have five layers: Epithelium, Bowman's membrane, Stroma, Descemet's membrane, Endothelium.
Emmetropia
Normal distance vision in which basically no refractive error is
present and distant images are focused sharply on the retina with no
need for corrective lenses or glasses. Opposite of ametropia.
Excimer Laser
Type of laser using so-called excited dimers (Excimer) to create
laser radiation. An example is the argon-fluoride laser (wavelength:
193 nm) which is frequently used in ophthalmology to remodel the
corneal stroma, often after lifting a corneal flap made by femtosecond
laser or microkeratome. Argon-fluoride excimer laser ablates tissue
without causing any damage to adjacent stroma in a precisely controlled
manner.
Femtosecond
1 fs = 1 Femtosecond = 10-15 second
A femtosecond is one billionth of one millionth, or one quadrillionth of a second. Lasers with femtosecond pulses enable precise and unique procedures, due to their exceptional physical properties.
Femtosecond Laser
The femtosecond laser uses infrared light with spot sizes as small as a few microns and laser pulse durations which are several orders of magnitude shorter than those of an Excimer Laser.
Hyperopia
A condition in which the eye is too short or the cornea is too flat
(the eye's focusing mechanism is too weak) thereby, preventing light
rays from focusing before reaching the retina. This causes an inability
to see near objects clearly. Hyperopia is the opposite of myopia.
Laser Assisted In-Situ Keratomileusis, LASIK
An advanced laser procedure using the precision of the excimer
laser to reshape the cornea, thereby decreasing or eliminating myopia,
hyperopia, and astigmatism. The refractive surgeon uses a femtosecond
laser or a microkeratome to create a thin, hinged layer of the cornea.
This flap is then lifted, folded back and the exposed surface is
reshaped using the excimer laser. After altering the corneal curvature,
the flap is replaced and adheres without sutures.
Microkeratome, mechanical
A surgical device for creating a flap of corneal tissue used in LASIK and some transplant techniques. It is affixed to the eye by use of a vacuum ring, flattens the cornea with an applanation plate, and then cuts across the cornea under the plate. The mechanical microkeratome uses a very sharp and thin metal blade.
Myopia
A condition in which the eye is too long or the cornea is too steep (the eye's focusing mechanism is too strong) thereby, causing light rays to focus before reaching the retina. This causes an inability to see distant objects clearly. Opposite of hyperopia.
Presbyopia
A condition associated with aging in which the normally soft and flexible crystalline lens of the eye hardens and becomes less elastic. This loss of flexibility limits the ability of the eye to change its point of focus from distance to near, which results in an inability to see near objects clearly.
Wavefront
Wavefront technology produces a detailed map of the refractive errors of the individual patient's eye. Wavefront analysis works by measuring and detecting the distortion or irregularities of the eye, known as aberrations, which cannot be detected by a traditional eye examination. Each patient has a unique visual optical system; hence wavefront data are like a fingerprint and can be used for personalizing a refractive laser treatment.
