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Laser Eye Surgery
LASIK
LASIK has been developed from PRK and has been used since the early 1990's.
LASIK is the combination of a surgical incision (keratomileusis) and the laser technique. The incision technique in conjunction with the preciseness of the laser provides for a good predictability and for a quick rehabilitation period for even high refractive errors.
Synonym:
Laser-in situ-Keratomileusis
Indication
— Nearsightedness up to ca. -10 dpt.
— Farsightedness up to ca. +3 dpt.
— Astigmatism up to ca. -4 dpt.
Over 90% of all patients with refractive errors are eligable for the LASIK procedure. Therefore, LASIK is the most used refractive procedure to correct nearsightedness, fearsightedness or astigmatism.
Properties
— good predictability when used for the proper indications
— correction in the optical center in the stromal bed of the cornea
— quick rehabilitation period with very little fluctuation in vision
— generally no postoperative pain
— non-reversible effect
The procedure
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Suction procedure For fixation purposes, a suction ring is placed on the eye prior to surgery. The eye is put under pressure for a brief period of time. |
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Preparation of the cornea With a precision knife, an incision is placed to create a thin flap of the cornea (0.16 mm). If a laser is used instead of the knife, the procedure is called Femto-LASIK. |
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Exposure of the stromal bed of the cornea The corneal flap is flapped back like a book cover. |
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Application of the laser |
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Closing of the wound The corneal flap is repositioned back onto the stromal bed. It sticks to the corneal tissue on its own and acts like a bandaid. |
With the correction of the refractive error shifted to the inner part of the cornea, LASIK offers major advantages in the healing process:
— The healing takes place all on its own inside the corneal tissue
in a controlled manner.
— Generally, the healing process is quick and free of pain.
— You will regain your full vision quickly.
— Only a few postoperative appointments are necessary.
Interesting LASIK facts
The optical zone, in which ablation of the corneal tissue takes place with the LASIK method, has a diameter of 6mm or at least the size of the pupil.
In order to ensure stability of the cornea, at least 250µm of corneal tissue must remain under the flap.
The flap itself has a thickness of 110 - 180µm, depending on the keratome used (femtosecond laser or microkeratome).
According to Munnerlyn, 131µm of corneal ablation are needed for the correction of 10 diopter and an optical zone of 6mm. As a rule of thumb: 15µm per correctible diopter.
Calculation example:
For the safe correction of 10 diopter, a minimum preoperative corneal thickness of 570µm is required:
250µm [remaining corneal tissue] + 180µm [flap] + 140µm [laser ablation]
