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Glossary of Refractive Surgery / Laser Eye Surgery: LASIK, LASEK PRK
ablating in surgery means to remove
Astigmatic Keratotomy; a refractive surgical procedure to reduce astigmatism with small arcuated incisions in the corneal edge
ability of the eye to focus the close-up-range
a warping of the curvature of the cornea so that light rays do not meet in a single focal point but in a distorted, elongated "point"
protein layer underneath the epithelium; connects the epithelial layer with the subjacent stromal layer
transparent, curved front part of the eye that covers the iris, pupil, and anterior chamber, providing most of an eye's refractive power
process of mapping the surface details of the cornea by using colors; used to determine the radii of the curvature of the corneal surface as well as the extent of the astigmatism or other irregularities
a congenital or acquired opacity that develops in the crystalline lens of the eye or in its envelope
destroyed, broken-up tissue between the flap and the residual corneal stroma
Diplopia; two eyes are not correctly aligned while aiming at an object => ghosting
or dioptre; refractive power of a lens or curved mirror; is equal to the reciprocal of the focal length measured in meters; a -3 diopter lens brings parallel rays of light to focus at 1/3 meter Diffuse lamellar keratitis; Diffuse lamellar keratitis; sterile inflammation of granulocytes; occurs mostly between the 1st and 10th postoperative day, but also much later; DLK can be accompanied with severe wound healing dysfunction
(Keratoconjuncivitis sicca = Sicca Syndrome) decreased tear production leads to a dry conjunctiva (Conjunctivitis sicca) and cornea (Keratitis sicca); common symptoms of dry eye include feelings of stinging and burning of the eyes
dys- = difficult, mal; trophy = supply, nutrition
the condition of having no refractive error
a device called epi-keratome slides over the surface of the cornea into the epithelial layer; the resulting "epithelial flap" is reflected and laser ablation can take place
outermost cell layer that covers the surface of organs
an ultraviolet laser used in refractive surgery since 1986 to remove corneal tissue How does an excimer laser work?
(All-Laser-LASIK) an femtosecond laser cuts a thin corneal (flap) by creating exact intrastromal explosions in the frontal section, after flap reflection an Excimer-Laser is used for the correction of refractive error
a laser that emits highly intensive light pulses lasting only femtoseconds; advantages are a high peak intensity and low energy transmission to surrounding tissue
a thin corneal cap with a hinge, cut by a microkeratome or a femtosecond laser
diplopic images; due to opening of the pupil beyond a small or decentered optical zone
difficulty to see in bright natural or artificial, direct or reflected bright light that leads to a reduction of brightness of the rest of the scene by constriction of the pupils, a loss of contrast sensitivity of the rest of the scene by scattering of the bright light within the eye
temporary or persistend increase of the intraocular pressure (IOP) => atrophy of the optic nerve = optic neuropathy => partial or complete loss of the visual field
Haloes; is a ring of light that surrounds a shining object; in laser eye surgery a misconfiguration of the optical zone causes scattered light; the bigger the pupil size the bigger the halos What does this look like?
caused as part of a wound response with local inflammation after Epi-LASIK, LASEK, PRK and rarely after IntraLASIK, LASIK; observed as a mild to severe whitening of the normally clear cornea
Hypermetropia; Farsightedness; a condition in which light rays are focused behind the retina => distant objects are seen more clearly than near ones.
implantable contact lens - additional lens for the correction of refractive error; implanted between iris and natural eye lens in the posterior chamber of the eye (Posterior Chamber Lens)
intra corneal ring segments (Intacs) - extremely thin, arcuate plastic segments implanted at the edge of the cornea and sparing the center of the cornea
the most visible part of the eye, works like a aperture to reduce or increase the incoming light to the retina
popular kind of anterior chamber lens, attached to the iris
"bulging" of a thin instable cornea due to the normal or increased intraocular pressure (IOP)
Inflammation of the cornea
LOCS; increasing loss of visual acuity / contrast vision in diminishing light when the pupil size increases
Laser-Assisted Subepithelial Keratectomy; by using alcohol (LASEK) the uppermost epithelium layer is shoved aside before the laser treatment is started
Light Amplification by Stimulated Emission of Radiation
Laser in situ Keratomileusis, the surgeon uses an instrument called microkeratome to cut a thin circular flap of corneal tissue, opens the flap like a hinged door, vaporizes the targeted tissue in the corneal stroma beneath it with the excimer laser, and then replaces the flap
automatic device to cut the cornea; uses an oscillating blade to cut the cornea creating a cap with a hinge
Shortsightedness, a condition in which light rays are focused before the retina => close objects are seen more clearly than distant ones.
a reduced number of functioning nerves in the flap reduces the frequency of eyelid movements => the tear film is insufficient => the epithelium is damaged
due to a strong increase of intraocular pressure during the suction process for the microkeratome incision or for the femtosecond laser incision barotrauma and/or insufficient ocular blood supply cause nerve fibres of the optic nerve to die
(OZ) this term means the planned diameter of the laser ablation in which the light is refracted to produce a good optical image; it is not to be confused with the effective optical zone existing after laser ablation and healing process - the diameter of this zone is usually smaller
before the surgery
implantable contact lens - additional lens for the correction of refractive error; implanted between iris and natural eye lens in the posterior chamber of the eye
after the surgery
defective accommodation and inability to focus sharply for near vision due to aging processes and loss of elasticity of the lens
A circular opening in the center of the iris through which light enters the eye
Diameter of the pupil in mm, in refractive surgery measured for photopic(daylight vision), mesopic (twilight vision), scotopic (night vision)
epithelium is scraped and then the laser sculpts the central optical area of the cornea
the ability of the eye to bend light as light passes through the eye, measured in diopters
automated measurement of refractive power by an electro-optic system
determination of the refractive power of the eye lens; series of lenses in graded powers are presented to determine which provide best-corrected visual acuity for the patient
surgical corneal procedure for the correction of refractive error like IntraLASIK, LASIK, Epi-LASIK, LASEK, PRK, ICL, Iris Clip Lens, RK
thin layer of neural cells that lines the back of the eyeball and forms the optic nerve
kind of refractive surgery to treat low to moderate myopia; microscopic incisions are placed in radial pattern on the cornea, causing it to flatten
daylight vision; colour perception is ensured by rods, luminance > 3-30 cd/m2 means photopic visions
twilight vision; both rods and cones contribute to colour and dim/bright perception, luminance ranges from 0.03 - 3 cd/m2
no colour perception because only light sensitive rods are responsible for vision, scotopic vision ranges from the perception threshold at 3 · 10-6 cd/m2 up to 0.003 - 0.03 cd/m2 luminance
the average spherical power of a spherocylindrical lens i.e. [magnitude of 1st order aberrations like myopia, hyperopia] + [magnitude of 2nd order aberrations like (astigmatism / 2]; example: [- 2 D myopia] + [-0.5 D astigmatism x X° / 2] = -2.25 D
sharp rays of light sent by a light source, type of starring
striae: grooves located in the Basement Membrane of the Flap, rarely located in the residual stroma uppermost layer
Topography-Assisted LASIK: laserablation guided by individual corneal topography data
Transient Lightsensitivity Syndrome; strong light sensitivity, occurs especially after IntraLASIK; average duration of 100 days
a procedure to measure the refractive errors of the first degree (myopia, hyperopia), second degree (astigmatism up to the seventh degree; perfect waves of light are sent through the visual system and compared with the waves of light leaving the eye
acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye, the sensitivity of the nervous elements, and the interpretative faculty of the brain
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