Non-contact holmium: YAG laser thermoplasty

The general impression is that the incidence of presbyopia is very low, but in fact, nearly 35% of people over the age of 40 have +1.00D or +2.00D hyperopia, and some countries are close to half. Currently, non-contact sputum: YAG laser corneal thermoplasty (LTK) is an effective, safe and simple method for the treatment of hyperopia, and its surgical effect can be maintained for more than 10 years. There is already a non-contact :YAG laser corneal thermoforming system for LTK approved by the US FDA. The system can simultaneously emit an annular array of 8 lasers onto the cornea through the firing system equipped on the slit lamp without touching the cornea. To correct hyperopia, two sets of 8-point holmium lasers are applied to the cornea. The laser energy causes the tissue to collapse at 16 o'clock on the cornea, causing the central cornea to become steep and achieve the effect of correcting hyperopia. The advantages are that the operation is time-saving, the operation is simple, the patient suffers little, and the postoperative complications are few. At present, some people have started to do 32-point LTK surgery, but no results have been reported. The latest research shows that the use of radiofrequency corneal diathermy is better and more durable. Treating diseases: hyperopia Indication 1. The FDA-approved 16-point LTK treatment range is between +0.75D and +2.50D, and astigmatism does not exceed 0.70D. Low-grade hyperopia over 50 years old (with a spherical lens within +1.50D and astigmatism within 0.50D) is the best indication. Low-degree hyperopia of 40 to 50 years old is also the scope of indications. For young patients under the age of 40, the most prominent problem is the refraction of refraction and poor surgical results. From the statistical results, the overall effect is that patients in the 40-45 age group are not as good as those in the 50-55 age group. The latest data show that the age-related drift to hyperopia in the LTK method is a natural process, not a disadvantage of the LTK itself. Therefore, the preoperative refractive state is stable In the first half of the year, the postoperative change was less than 0.50D. 2. For some patients with emmetropia, they may be willing to turn non-dominant eyes into myopia for reasons such as presbyopia, so as to work close-up. 3. In fact, patients who are suitable for LTK may also be suitable for LASIK. The doctor needs to be flexible according to the patient's condition. LTK has certain advantages over LASIK in the following situations. For example, if you have fear of corneal flap in LASIK surgery, it is more suitable for LTK. Patients with corneal flattening have more difficulty or danger in doing LASIK surgery. The corneal flap on the cornea of the basal membrane dystrophy has a greater risk of complications, and LTK is not a contraindication. I have done LASIK hyperopia correction surgery at a glance, and the results are not satisfactory. I can consider LTK. For hyperopic patients with large pupils, treatment with large diameter LTK may be more appropriate for patients. Contraindications 1. The patient has unrealistic expectations and goals for surgery. For example, a patient cannot receive a myopia reaction for a period of time after surgery. 2. The refractive state is unstable. 3. Corneal inflammatory diseases, corneal bulging diseases, dry eye diseases, and the like. 4. Systemic diseases such as collagen vascular diseases, immunodeficiency diseases, and the like. 5. Eyeball tremors. Preoperative preparation 1. Preoperative examination. Refer to PRK preoperative examination (eye and refractive examination). 2. Decide which calculation form to use (6 months, 12 months or 24 months) according to the patient's eye requirements (habit, occupation, etc.), age, diopter, etc. Many doctors use a 6-month calculation sheet because the patient is satisfied with the rapid vision after surgery. It has been suggested to use a 24-month calculation for non-dominant eyes to make it slightly overcorrected. These problems should be discussed with the patient before surgery, including the speed of vision recovery. Because the treatment is very fast and simple, you can discuss the post-operative retreatment with the patient before surgery. Telling the patient that near vision may decrease with increasing distance vision, otherwise the patient will feel dissatisfied after surgery (although myopia may be improved compared with preoperative). 3. Explain to the patient about the procedure and guidance of the operation before surgery, and emphasize the importance of maintaining fixation. In addition to occasional fever and mild tingling during laser emission, there is generally no discomfort. 4. Machine preparation. Surgical procedure 1. The corneal surface anesthetic was dropped twice, at intervals of 3 minutes, and the opener was opened. The contralateral unsurgical eye pad is covered with an eye pad. 2. Let the cornea dry for about 3 minutes. This process is very important because the energy of the krypton laser is absorbed by water. The standard method is natural drying, but when the cornea is applied with a topical anesthetic, the epithelium becomes irregular. Therefore, it is recommended to apply a balanced salt solution on the cornea of the epidermis to wipe off, which makes the corneal epithelium dry more evenly. It has been found that the corneal moisture distribution is not uniform, so wipe it off horizontally and vertically with a squeezed damp sponge sponge swab and then dry. Be careful not to change the time it takes the cornea to dry for 3 minutes, as all current calculations are based on it. If the time is less than 3 minutes, it may cause under-correction or even ineffectiveness. More than 3 minutes may cause over-correction. During the dryness of the cornea, let the patient look at the flashing fixation lamp and do not turn around the eyeball. 3. Laser emission. The laser is focused, and the laser should start to be emitted as soon as the drying time of 3 minutes is reached. Just tell the patient to hold your breath before the laser is launched. The laser time is 3 seconds. Be careful not to loosen the foot switch before the laser is completed, so as to avoid the laser being incomplete and undercorrected. The machine's timing system automatically stops firing 2 minutes after the 3min drying period, but it is best to control this time within 30s. If you are unskilled, you can pause between 6mm and 7mm treatment to check the focus and whether it is centered. For the skilled person, it can be carried out continuously without stopping. 4. Drop antibiotic eye drops and non-hormonal anti-inflammatory drugs (NSAID). complication Very few complications. There may be short-term overcorrection, refractive retraction, etc. Occasionally, the laser spot is deviated due to the movement of the eyeball in the patient, but there have been no reports of severely affected vision.

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