laser in situ keratomileusis

The principle of laser in situ keratomileusis (LASIK) evolved from Barraquer's work and the concept of keratomileusis. The modern technology of LASIK was first completed by Brint and Slade, which used a microscopic keratome with a gear to make a corneal flap under topical anesthesia. After the light cut of the corneal stromal bed, the corneal flap was repositioned without suturing. The corneal flap has the distinct advantage of reducing irregularities in the cutting surface and protecting the light cutting surface (preventing various healing processes). Treatment of diseases: astigmatism myopia Indication Laser in situ keratomileusis is suitable for: 1, there are requirements for the removal of glasses, generally 18 years of age, under 50 years of age (although for some special circumstances, the literature is LASIK patients are younger than 18 years old). 2. The diopter is stable for 2 years. If a contact lens is worn, the soft lens should be worn for 2 weeks, while the rigid lens should be worn longer. 3, can be corrected -0.50D ~ -15.00D myopia, 0.50D ~ 5.00D far vision and 8.00D astigmatism. For hyperopia correction, postoperative recovery time is longer. For hyperopia greater than 6.00D, the best corrected visual acuity often decreases after surgery. 4, both eyes anisometropia is a good indication. 5, eye examination without surgical contraindications. 6. Patients who need LASIK after PRK or penetrating keratoplasty should be performed at least 1 year later. Radial keratotomy (RK) should be performed 2 years later. Contraindications 1, there is active inflammation of the eye. 2, suffering from keratoconus, dry eye disease, corneal endothelial lesions, glaucoma, retinal detachment and other eye diseases. 3, there are other obvious vitreoretinopathy may occur in the eyes of retinal detachment. If there have been cases of fundus bleeding or retinal detachment surgery. For dry retinal tears or retinal degeneration, retinal photocoagulation is required for at least 2 weeks before LASIK can be considered. 4, the thickness of the cornea is too thin (generally less than 450m), corneal swelling may occur after corneal LASIK; corneal curvature is too small, such as less than +380, easy to form free flap during surgery. 5, corneal surface turbidity, repeated epithelial erosion, epithelial basement membrane disease, etc., should not choose LASIK, but can consider PRK. 6. The cleft palate is too small. It is difficult to place the negative pressure ring of the microkeratome during surgery. Therefore, it is considered to be a PRK for low-to-moderate myopia. For moderate to above myopia, it can be cut open during surgery. 7. Correct amblyopia with poor vision. 8, surgery can not cooperate. 9, scar constitution, diabetes, collagen disease, etc. may affect corneal wound healing. Systemic lupus erythematosus and rheumatoid arthritis are prone to corneal lysis after surgery. 10, high myopia eye cutting is relatively deep, light cutting diameter is small, there is the possibility of glare discomfort after LASIK surgery, is cautious for drivers who often drive at night. 11, AIDS and other diseases. Preoperative preparation 1. Preoperative routine examination: visual acuity, corrected visual acuity, retinoscopy after astigmatism and computer optometry, corneal topography, ultrasonic corneal thickness, intraocular pressure, slit lamp microscopy. 2. Explain to the patient the simple principle of the operation, the surgical procedure, and the possible occurrence of the operation. The patient or his relatives sign the surgical consent form. 3, 1 to 3 days before surgery, local antibiotic eye drops, 1% pilocarpine eye drops 1 time before surgery. 4, according to corneal surgery before surgery, eye drops, disinfection. Surgical procedure 1, the patient comfortably supine, adjust the head position, the eye order is fixed to the first right eye and the left eye. Check the patient and the eyes are correct. 2, 0.5% tetracaine or 0.4% Benelux or other topical anesthetic, eye drops 5 to 10 minutes before surgery, 2 to 3 times. 3. Operate under sterile conditions, spread the towel, stick the upper and lower eyelid film strips, open the sputum, and rinse the conjunctival sac. Let the patient look at the built-in fixation lighting of the machine and be familiar with the sound emitted by the laser machine. 4. Corneal marking. The pen ink or gentian violet was marked with a special operation, the center of the pupil was marked with a dot, and the opposite side of the corneal flap was made with a radial marker for the purpose of accurately placing the negative pressure ring and the flap. In particular, if there is a risk of forming a free flap, radial marking must be done to avoid difficulty in resetting the free flap. 5, corneal flap production. There are many types of microkeratome for LASIK surgery, and the following factors should be considered when choosing. 1 safety and repeatability; 2 smooth and smooth cutting surface (including blade quality problems); 3 operation and maintenance is simple; 4 performance and price ratio is reasonable. At present, there are a variety of microkeratomes (mechanical, water jet, laser plate cutting) that are used many times, as well as disposable microkeratomes. Mechanical microkeratomes are widely used, and can be divided into manual and automatic according to driving force. Manual operation requires a higher level of the operator, and automatic operation is relatively simple, but in the event of a mechanical failure, processing is sometimes difficult. Therefore, the surgeon is required to have a comprehensive understanding and mastery of the structure, working principle, maintenance, and handling methods of the microkeratome. 6, laser cutting. 1 Determine the corneal optical center. Let the patient look at the fixation light and adjust the aiming laser so that the midpoint of the focal plane is just at the front surface of the cornea where the center of the pupil is located. 2 Flip the corneal flap. Use a sponge swab or drain strip to remove excess fluid from the conjunctival sac, flip the flap and expose the corneal stroma. The corneal flap is preferably padded behind the corneal flap so that the corneal flap has a certain spatial distance from the surface of the eyeball to prevent the siphoning liquid from reaching the corneal cutting surface and affecting the laser cutting. 3 laser cutting. The aiming light is slightly adjusted so that the focal plane is falling on the anterior surface of the matrix and the optical center of the cornea. At the time of cutting, it is difficult to see the spot on the exposed corneal stroma, and sometimes it is judged by the spot projected on the edge of the iris or pupil. During light cutting, eye position, aiming position, and focus should be closely monitored. Once the eyeball has rotated a lot, stop cutting immediately to avoid off-center cutting. At the same time, attention should be paid to the distribution and tissue reaction of laser cutting. When the surface of the cornea is hydrated unevenly or the liquid is too much, it should be dried with a sponge and then continue. When the cutting amount is large and the continuous cutting gas mist is large, it may be paused in the middle of the cutting as the case may be. Due to LASIK's light-cutting, the patient's fixation of fixation light is not as clear as in PRK surgery, sometimes resulting in difficulty in gaze. The brightness of the illumination can be lowered as much as possible to make it easier for the patient to see the fixation lamp. If the eye position is very correct, let the patient not look for the target. If the patient is unable to fix it, the fixed eye can be used to fix the eye position. 7, corneal flap reduction. After the cutting is completed, the corneal stromal bed is rinsed with BSS. After the corneal flap is reset, the blunt needle is used to extend under the valve and rinsed carefully. Then, use a sponge swab to align the pedicle of the flap to the opposite side, gently wipe the corneal flap from the center to the periphery, and absorb the moisture at the edge of the flap. It is necessary to ensure that the edge of the corneal flap is uniform, the surface is free of wrinkles, and there is no foreign matter at the interface. At present, a corneal flap flattener has been designed. The head end of the instrument is a transparent concave lens, which is pressed against the corneal flap. The rapid rotation of the wrist is used to reset the corneal flap and avoid the occurrence of corneal streaks. During operation, the operator can clearly observe the flow of liquid from the layers. It is best to wait 2 to 3 minutes after the flap is reset, so that the corneal flap has enough time to stick firmly. 8. After removing the opener and the film, let the patient blink a few eyes and make sure that the corneal flap is not displaced. 9. Check the corneal flap under the slit lamp for good recovery, no foreign matter under the flap. 10, surgery eye drops antibiotic eye drops and artificial tears, with a hard eye mask with holes to protect. The paralyzed patient should not take it off and review it the next day.