• Aberrometer

    An instrument which measures the total refractive error and abberations of the optical system of the human eye using wavefront analysis.

  • Accommodation

    Ability of the natural lens to change its shape to focus on close objects. 

  • Ammetropia

    Eye abnormality such as nearsightedness, farsightedness, or astigmatism. Light rays are focused behind (nearsightedness) or in front (farsightedness) rather than on the retina resulting in blurry distant or near vision. 

  • Anterior chamber lens

    Artificial lens implanted between the cornea and iris of the eye into the anterior eye chamber. 

  • Artificial Lens

    Lens implant made out of PMMA, acrylate or silicone. Implanted into the eye to correct an existing refractive error. Most commonly used during cataract surgery when the opaque lens is removed and replaced. In contrast, phakic lenses are implanted in addition to the natural lens to correct higher refractive errors. See anterior chamber lens, posterior chamber lens, phakic lens.

  • Artiflex, Artisan

    Phakic anterior chamber lenses made out of foldable acryl by OPHTEC. Implanted into the anterior chamber of the eye between the cornea and the iris as an additional lens.

  • Aspherical correction

    Innovative ablation profile used for eye laser surgery such as LASIK or LASEK. Eliminates imperfections of the refracting power of the eye and achieves better twilight and night vision.

  • Astigmatism

    Always present if the corneal surface differs from the ideal ball-shape curvature. One of the most common refractive errors, corrected with cylindrical lenses.

  • Acufocus

    Corneal implant for presbyopic patients by AcuFocus. Implanted in one eye only it allows some independence from reading glasses. See also KAMRA inlay.

  • Add (addition)

    Indicates presence of presbyopia. The value, for example +2 dpt, is added to the spherical correction.

  • Argon-Laser

    Laser used for photocoagulation. Therapeutically used to treat macular degeneration, diabetic retinopathy, retina holes.

  • Astigmatic Keratectomy

    Corneal procedure using a femtosecond laser to reduce astigmatism of 3 dpt or more by placing small, arch shaped incisions at the periphery of the cornea.

  • Axis

    Indicates the axis of astigmatism in degrees.


  • Barraquer, José I.

    José I. Barraquer (1916-1998) is acknowledged to be the father of refractive surgery. His life’s work was dedicated to the idea of reshaping the cornea to change the eye’s refractive power. 

    Born in Spain, he moved to Bogota, Colombia, in 1953. There, he founded the Barraquer Institute of America, where he trained many of the refractive surgeons practicing around the world today. Barraquer designed the cryolathe and the microkeratome and developed keratomileusis and keratophakia, laying the groundwork for LASIK and other modern lamellar procedures.

  • Bioptic, Bioptics

    Procedure combining a phakic lens implant and LASIK. The phakic lens corrects high and extreme refractive errors, the LASIK (performed 2 – 3 months after the lens procedure) allows to correct any residual refractive error providing impressive gains in spectacle-corrected visual acuity as well as good predictability.

  • Cataract

    Opacity or clouding of the natural crystalline. Cataracts occur naturally at an advanced age but can also be induced earlier due to eye trauma, radiation or certain prescription drugs. If visual loss becomes significant, the opaque lens can be replaced with a clear intraocular lens.


  • cyl (cylinder)

    Indicates the value of astigmatism in diopter, for example 1.5 dptr astigmatism. In Germany, negative cylinder values are used whereas in the US values are positive. 

  • Corneal thickness

    Crucial for corneal laser surgery. To ensure the stability of the cornea after laser ablation, only a limited amount of corneal tissue can be removed with the laser. Corneal thickness is measured using optical methods or ultrasound.

  • Corneal topography

    Process of mapping the surface details of the cornea. Individual irregularities such as astigmatism can be graphically shown. 

  • Contraindication

    In a medical sense: conditions making a certain medical procedure or treatment inadvisable. 

  • Convex Lens

    Lens with a bulging surface like the outer surface of a ball. Collects incoming rays of light so that the image is focused sharply on the retina. Convex lenses are plus power lenses used to correct hyperopia or farsightedness as well as presbyopia (reading glasses).

  • Concave Lens

    Minus power lens used to correct nearsightedness. A sharp image is produced by moving the focal point back onto the retina.

  • Cross-Linking

    Corneal collagen cross-linking with riboflavin is used to treat keratoconus and keratectasia, an extremely rare complication after LASIK surgery. Cross-Linking increases collagen crosslinks which are natural "anchors" within the cornea and therefore stabilizes the cornea.

  • Cycloplegia

    Mostly pharmacologically induced paralysis of the ciliary muscle of the eye, resulting in a loss of accommodation.

  • Customized Ablation

    LASIK procedure based on diagnostic values such as corneal topography or wavefront analysis. The goal is to optimize the visual correction by eliminating corneal irregularities.

  • Conductive Keratoplasty (CK)

    Type of refractive surgery that uses radio waves to adjust the contour and therefore refractive power of the cornea by shrinking corneal collagen. 


  • Diffuse Lamellar Keratitis (DLK)

    Rare, non-infectious or “sterile” complication after LASIK surgery characterized by inflammatory infiltrates under the corneal flap.

  • Diopter

    The unit of refractive power (refraction) of the eye, is indicated in negative numbers for nearsightedness and in positive numbers for farsightedness.


  • Excimer laser

    Ultraviolet laser disrupting the molecular bonds of the surface tissue which effectively disintegrates in a tightly controlled manner through ablation rather than burning. Has been used for corneal surgery procedures (for example LASIK or LASEK) since 1986.

  • Eye Tracker, Eye Tracking Systems

    Controll system integrated into modern eye laser systems to detect small spontaneous and involuntary eye movements during eye laser surgery. When detecting eye movements, the eyetracker automatically readjusts or stops the laser ablation.

  • Epi-LASIK

    Modified PRK with the epithelial cells removed by a mechanical microkeratome using a blunt, rather than sharp blade followed by a surface ablation. At the end of the treatment, the epithelial cells are repositioned over the central cornea. See also PRK and LASEK.

  • ELSA

    Excimer laser subepithelial ablation, see also LASEK.  

  • Emmetropia

    Normal vision. Rays of light are focused exactly on the retina.

  • Eye Laser

    Laser for therapeutic treatment in ophthalmology, e.g. for the correction of refractive errors (excimer laser), treatment of retinal disease (Argon laser), glaucoma or secondary cataract (YAG Laser).


  • Femtosecond laser

    An infrared "solid state" laser that delivers pulses of energy within the cornea, causing a small controlled explosion of gas that separates the layers of the cornea. The femtosecond laser is used to cut corneal tissue, such as a Lasik flap (Femto-LASIK).

  • Femto-LASIK or Femtec-LASIK

    LASIK procedure in which the corneal flap is cut with a femotsecond laser. Also called Laser-LASIK, All-laser-LASIK, Intra-LASIK or IntraLase-LASIK.

  • Flap

    Mass of corneal tissue vascularized by a pedicle, which is created by an incision with a microkeratome or femtosecond laser during the first step of LASIK surgery. The flap is opened prior to laser treatment and folded back onto the cornea afterwards. It protects the wound like a bandaid.

  • FLEx (Femtosecond lenticel extraction)

    Relatively new procedure for the correction of simple refractive errors. The femtosecond laser is used to separate a small piece of corneal tissue within the cornea which is then extracted resulting in a change of the refractive power of the cornea. FLEx does not require the use of an excimer laser. 

  • Flying Spot Laser

    A very small spot of excimer laser energy is applied in rapid succession at different locations across the ablation area. 


  • Glaucoma

    Group of chronic eye conditions that lead to damage of the optic nerve resulting in vision loss. In most cases, the damage is due to increased intraocular pressure.


  • Halo

    A known complication of refractive eye laser surgery such as PRK, LASEK or LASIK. Light sources can appear larger and blurry with circles radiating out from the center, especially under twilight and night conditions. 

  • Holmium Laser

    Infrared laser, therapeutical effects are achieved by temperatures / shrinking of tissue.

  • Hyperopia

    Also known as farsightedness or longsightedness. Hyperopia occurs when the eye is too short, causing light rays to be focused behind rather than on the retina. People with hyperopia can see distant objects sharply blut have difficulty seeing objects close up. 


  • Implantable Contact Lens (ICL)

    Additional lens for the correction of refractive errors which is implanted into the eye's posterior chamber, between the iris and the body's own lens.

  • IGEL

    Catalogue of medical services which, according to the German Medical Board (Bundesärztekammer), are not covered by the public health care providers and therefore have to be privately paid by the patient. All vision correction procedures are part of this catalogue. 

  • iLASIK

    Very precise, individual LASIK combining femtosecond laser flap creation and wavefront guided ablation. 

  • Indication

    In a medical sense: conditions favoring a certain medical procedure or treatment.


    Laser eyeprocedures for the correction of presbyopia. Minimal invasive procedure using only a femtosecond laser. Because no cuts are made to the corneal surface, risk of infection is minimized. 


  • Keratectasia

    Corneal ectasia is a rare but serious complication of LASIK surgery. If the laser removes too much tissue during LASIK or the flap is cut too deep, the structure of the cornea can be weakened. Thecornea then bulges forward causing an increasing astigmatism and distorted vision.Worldwide, only 43 cases have been described 88% of which could have been prevented by careful diagnostics or responsible treatment. See also Cross-Linking.

  • Keratoconus

    Cone-like bulging of the cornea. Keratoconus is a progressive, noninflammatory, bilateral (but usually asymmetrical) corneal condition characterized by stromal thinning and weakening that leads to corneal surface distortion. Visual loss occurs primarily from irregular astigmatism and myopia, and secondarily from corneal scarring. See also Cross-Linking.

  • Keratome

    An automatic precision knife used to cut the corneal flap during LASIK surgery. Alternatively, a femtosecond laser can be used (Femto-LASIK).

  • Keratomileusis

    A refractive surgical technique developed by José Barraquer (1916-1998) where a partial circular flap of corneal tissue is removed, frozen, reshaped and replaced upon the cornea. 



    LASer Epithelial Keratomileusis, see also ELSA. An alcohol solution is used to soften and detach the corneal epithelium which is then rolled back into a flap. Following the excimer laser ablation, the flap is repositioned over the cornea.

  • Laser

    Abbreviation for Light Amplification by Stimulated Emission of Radiation. Device which sends out monochromatic (unicolored), parallel light beams. The wavelength of the light beams determines its character.


    Laser in Situ Keratomileusis. Laser ablation inside the cornea within the stromal bed (in contrast to surface ablation techniques such as PRK or LASEK).

  • LASIK TÜV Süd Certificate

    The LASIK TÜV Süd certificate, initiated by and developed under the guidance of the VSDAR, is based on an ISO 9001:2008 certification and requires an additional evaluation by external auditors (patient outcomes, experience of the surgeon, number of performed surgical procedures, complication rates, hygiene standards, technical equipment and patient satisfaction).

  • Lens implant

    Artificial lens implanted into the eye to correct an existing refractive error. Most commonly used during cataract surgery when the opaque lens is removed and replaced. In contrast, phakic lenses are implanted in addition to the natural lens to correct higher refractive errors. See anterior chamber lens, posterior chamber lens, phakic lens.

  • Lens replacement

    The exchange of the body's own lens with anartificial lens / lens implant.

  • Lens surgery

    Implantation of an additional lens (see phakic lens) or exchange of the body's own lens with an artificial lens (see lens exchange).

  • Local anaesthesia

    Loss of sensation in the surgical field. The local sensation of pain in the operated eye is eliminated while the patient remains fully conscious. The effect is usually attained with eye drops.


  • Myopia

    Also called nearsightedness,  a type of refractive error of the eye. Light entering the eye is focused in front of the retina due to an eye too long or a cornea with too high refractive power. Distant objects appear blurred. 

  • Microkeratome

    An automatic but hand-held precision knife used for incisions to produce a corneal flap during LASIK surgery.

  • Monovision

    A technique to limit the effects of presbyopia by correcting one eye for near vision and the other for far vision.

  • Multifocal lens

    Artificial intraocular lens with several points of refraction for close-up, intermediate and distant vision. Multifocal lenses are implanted into the eye instead of the natural lens and provide relief for presbyopia at the same time as for nearsightedness or for farsightedness. Examples: AcrySof ReStor, ReZoom. 

  • Munnerlyn Formel

    Formula for the calculation of the corneal ablation d [in µ] in correlation to the diameter of the optic zone z [in mm], the refractive error p to be corrected [in dptr] and a laser specific constant düz

    Example: düz for Technolas 217z = 10%


  • Nd:YAG Laser

    Used in ophthalmology to correct posterior capsular opacification, a condition that may occur after cataract surgery, as well as  peripheral iridotomy in patients with acute angle-closure glaucoma.


  • Objective Refraction

    Determination of refractive power by automatic measurement with electro-optical systems.

  • Optical System (of the eye)

    Just as a camera has its lenses, diaphragm, and film, the eye has its cornea and lens to refract light, its pupillary aperture to optimally limit passage of light, and the retina to receive images. 

  • Overcorrection

    Overachievement of the effect of a surgery. A patient who used to be nearsighted is now slightly farsighted. A residual refractive error remains.


  • Pachymeter

    Medical device used to measure the thickness of the cornea prior to LASIK surgery.

  • Phakic Lens

    Artificial lens that is placed inside the eye in front of the natural crystalline lens to correct an existing refractive error. A phakic lens is placed either in front (anterior chamber lens) or immediately behind the iris (posterior chamber lens). 

  • PresbyLASIK

    A special LASIK procedure to correct near- or farsightedness with/without astigmatism as well as presbyopia by creating a multifocal corneal surface.

  • Presbyopia

    Part of the normal process of aging. As a person becomes older, the natural crystalline lens of the eye begins to lose its flexibility and therefore the ability to focus on objects in different distances, especially close-up. People 40 years and older therefore need reading glasses. 

  • Presbyopia Correction

    Reading glasses are the most commonly used devices to correct presbyopia. Surgical procedures available are Monovision LASIK, multiofocal lens implants (PRELEX), Intracor, PresbyLASIK or KAMRA inlay.

  • Photorefractive Keratectomy, PRK

    A surgical procedure using an excimer laser to reshape the cornea via surface ablation. Used if a patient’s cornea is too thin to cut a LASIK flap. See also LASEK.

  • Pupillometer

    Instrument for measuring the diameter of the pupil of the eye under different light conditions.


  • Refraction

    Determination of the refractive power of the eye or of the extent to which rays of light are bent, measured in diopter (dptr)

  • Radial Keratectomy (RK)

    Radial incisions are placed in the peripheral surface of the cornea with a diamond blade. This decreases the tension in the corneal center and allows the cornea to flatten. Because of the side effects, this procedure is no longer practiced.

  • Refractive Power

    Unit for the change of direction of a ray of light to a focal point, measured in diopter (dptr.)


  • Subjective Refraction

    Determination of refractive power by patient interview prior to prescription of glasses or contacts.

  • Sph (Sphere)

    Indicates values in diopter. Nearsightedness is indicated in negative values, for example -5.75 dptr. nearsightedness, farsightedness is indicated in plus values, for example +3.5 dptr.

  • Sicca Syndrome

    Dryness of the eyes, often due to decreased tear secretion or anormaltear film composition. Patients complain about red and tired eyes, sometimes in combination with foreign body sensations. Usually treated with artificial tears (eye drops). 


  • Toric lens

    Also called sphero-toric lens. Customized artificial lenses used for the correction of astigmatism. 

  • Topolink LASIK

    Individual correction of a refractive error based on the topography of the cornea in the optic zone. The refractive power of the corneal surface is corrected in the entire optic zone.

  • Topography

    Anatomical description of the dimensions and curvature of the corneal surface, see Topolink-LASIK.

  • TICL "toric implantable contact lens"

    Artificial lens which is implanted in addition to the natural lens of the eye to correct near- or farsightedness (spherical component) in combination with astigmatismus (cylindrical component of the refractive error).


  • Undercorrection

    The effect of a surgery has not been achieved in its entirety. A residual refractive error remains. Undercorrection often occurs where healing regresses more vigorously than predicted.



    Abbreviation for "Verband der Spezialkliniken Deutschlands für Augenlaser und Refraktive Chirurgie, e. V.", a non-profit organization. In English: Association of German Specialty Clinics for Eye Laser and Refractive Surgery. 

  • Visus

    Term for sharp vision used by ophthalmologists, indicated in logarithmic lines.

  • Veriflex, Verisyse

    Artificial lenses made out of foldable silicone which are implanted in addition to the natural lens into the anterior chamber of the eye.


  • Wavefront Technology

    Determines the entirety of the refractive error of the optic system. A wave of parallel rays of light is sent into the eye and focused on the retina. Upon exiting the eye, the reflected light ray is sent through an array of lenses and recorded by a CCD camera. An eye with ideal vision will reflect the light ray in a straight wave front. Each deviation of the straight ray represents a refractive error, which can be corrected with a laser on the cornea ("customized ablation"). 

  • Wavefront LASIK

    “Customized ablation" based on a wavefront analysis. Requires a flying spot laser and eye-tracking system.

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