Laser surgery to correct refractive errors
LASIK and PRK (LASIK) are used to reduce or eliminate farsightedness, myopia, astigmatism, and eliminate glasses, with the difference that LASIK cannot be performed on patients with high myopia.
In LASIK surgery, a layer of the cornea is cut and removed, and after it is shaved under it, the layer is put back in place. However, in PRK, the most superficial layer of the cornea is shaved and treated without removing it, and therefore, complications such as displacement of the cut layer of the cornea, etc. do not occur. The thickness of the patient's cornea is important in determining whether an ophthalmologist will recommend LASIK surgery. If the patient's cornea is too thin, LASIK is usually recommended over PRK. The patient's occupation also influences this choice. For example, patients such as boxers who are frequently hit in the eye are not suitable for LASIK surgery and are better off having LASIK.
The Food and Drug Administration (FDA) has approved the excimer laser for the correction of nearsightedness up to -12 diopters with -4 diopters of astigmatism, and farsightedness from +1 to +6 with +1 diopter of astigmatism. (Diopters are a measure of refractive error. Negative diopters are nearsighted and positive diopters are farsighted.)
Almost everyone who undergoes surgery wants to know what their chances are of achieving a satisfactory result. For low and moderate myopia (up to -7 diopters), about 95% of patients achieve unaided vision of 10.5 to 10.6 or better, and 85% have a chance of achieving unaided vision of 10.8 to 10.9 or better. This means that people are much less dependent on glasses, but they may need a lower prescription for more precise tasks such as driving, especially at night.
For high myopia (above -7 diopters), about 85% of patients achieve unaided vision of 10.5 to 10.6 or better, and 70% achieve unaided vision of 10.8 to 10.9 or better.
The Food and Drug Administration (FDA), in collaboration with the American Ophthalmological Association, considers the following to be suitable for LASIK:
You must be at least 18 years old (21 for some lasers), because the vision of people under 18 often changes.
For patients with presbyopia, LASIK does not correct refractive errors because one eye sees both far and near.
Eye doctors always recommend wearing glasses
However, there are a number of people who do not want to wear glasses and prefer to live without them. For this, there are two solutions available to these people, one is the use of contact lenses and the other is LASIK surgery. Contact lenses, which were introduced to the market nearly 90 years ago, are now easily available and used, and many of these people use this device to live without glasses and to a great extent aesthetically.
If contact lenses are not used properly, they increase the risk of corneal scarring, sensitivity, and eye discomfort, which is why experts were looking for an alternative and surgical procedures were studied.
The risk of LASIK surgery is much lower than that of lenses that are used, because using lenses always puts the eyes at risk, but in LASIK surgery there is only a risk of risk during the operation and the days after it. Of course, it should be noted that LASIK surgery also has its own specific conditions, for example, the person's eye number must be fixed and used based on the needs of the person.
Criteria for laser surgery
The criteria for LASIK and laser (PRK) surgery are:
» Minimum age of 18 years (preferably after the age of twenty) and at most until the person has cataracts.
» No significant change in the glasses score in the past year, meaning that the maximum has not changed more than 5.5 diopters.
» Sufficient corneal thickness
» Myopia -1 to -10 diopters
» Astigmatism 0.5 to 6 diopters
» Hyperopia up to +6 diopters
» No quaticonus (cornea cone) or irregularities on the surface of the cornea
» No general diseases such as rheumatism, advanced diabetes and immunodeficiency
» No pregnancy or breastfeeding
» No eye diseases such as glaucoma (black water), cataracts, moderate to severe dry eyes and herpes zoster,
» No dilation of the pupil in the dark
» Having realistic expectations of the capabilities and capabilities of laser surgery (PRK) or LASIK in vision correction.
If you use soft contact lenses, stop using them at least one week in advance.
If you use rigid gas-permeable contact lenses, stop using your lenses at least 3 to 4 weeks in advance.
If we suspect that the corneal changes caused by the lenses have not returned to normal after removing the contact lenses, the measurement of the refractive error (determination of the glasses score) is repeated every one to several weeks until the refractive error is fixed, and then preoperative tests are performed.
A complete ophthalmological examination includes: slit lamp examination, measurement of eye pressure, examination of eyeball movements and examination of the posterior parts of the eye, namely the nerve and retina (after applying dilating drops), and a detailed assessment of the refractive error (glasses score) and the level of vision is performed.
Special color photographs called topography and pachymetry or orb scans are taken to evaluate the cornea in terms of measuring the thickness of the cornea and the absence of keratoconus and irregular astigmatism and examining the details of the optical map of the corneal surface. After obtaining sufficient information and awareness of the capabilities and limitations of the procedure and with realistic expectations, decide to operate.
Preoperative care
The day before the procedure, take a shower and wash the edges of the eyelids well with diluted baby shampoo. On the day of the procedure, do not wear perfume, cologne or makeup.
Do not use perfumes (the laser device is sensitive to odors) and avoid wearing makeup around the edges of the eyelids.
The surgery is an outpatient procedure and takes 10 to 15 minutes for each eye. Before the procedure, anesthetic drops are placed in the eyes. You will not feel much pain during the procedure. The eyelids are disinfected with betadine solution. Then, you lie on your back on the bed in the laser room and anesthetic drops are placed in your eyes again. Your eyelids are held apart with a special device and the operating room microscope is placed in front of your face. Inside the microscope, there is a small red light that is initially fixed and flashes during the laser treatment. To increase the accuracy of the correction, you should stare at this light regularly (especially when you hear the whirring sound of the laser).
Postoperative risks:
Over- or under-correction (overcorrection of refractive error: negative number of positive or negative number of negative) may occur, in which case further surgery, contact lenses or glasses may be required. Other complications are listed below, many of which resolve over time.
» Glare,
» Seeing halos or starbursts from lights at night
» Corneal infection: Fortunately, vision-threatening complications such as infection are extremely rare.
» Reading glasses may still be required after surgery.
» Some patients may be better off without glasses after LASIK than before, but may still need glasses to see well.
» Disturbances such as reduced sharpness of vision, and even with 10/10 vision, objects may appear blurry or brown.
» Sensitivity to light.
» Dryness.
» Scratching.
» Myopia at night: Since only the central part of the cornea is deformed in this procedure, when the pupil opens at night, light enters the eye from the unaltered cornea, causing myopia. Even if there is excellent vision during the day, at night, you may need a small pair of glasses for complete vision.
The most important complications of LASIK are complications that cause vision loss in one or both eyes, and this vision loss cannot be corrected with glasses. The causes of vision loss in these patients are mainly irregularity or corneal opacity. One of the causes of corneal irregularity is the development of keratoconus or corneal hump after surgery, which is more common in LASIK and femto-LASIK than in LASIK and PRK. However, corneal opacity occurs as a result of postoperative inflammation or infection. Fortunately, the above complications are very rare and are preventable by more than 90 percent. However, if they do occur, their treatment, although possible, is somewhat difficult and will require treatment and follow-up procedures. Although many of the above complications can be reduced with preventive measures, they are still rare.
Postoperative care
After LASIK surgery, your eyes will experience burning, pain, and a foreign body sensation for 2 to 3 days, and especially the first night, you may have severe pain that requires more painkillers, but do not worry. Resting in a semi-dark room and using an ice compress and a dry towel or cloth that you have placed in the refrigerator will help to tolerate this pain.
Do not rub your eyes in the first few days after surgery. To apply eye drops, just pull down the lower eyelid and drop the drop into the eye. Never touch your upper eyelid.
Try not to put pressure on your eyes. In the first weeks after surgery, vision changes (your vision is sometimes blurry and sometimes clear), a slight burning sensation, and sometimes a headache are normal. However, if you have severe and progressive pain and blurred vision, or if you feel like you had the first few moments after surgery, be sure to see your doctor. Driving is safe after a few days.
You can take acetaminophen-codeine tablets every 4 hours if you have pain.
» Use eye drops as directed by your doctor.
» Eye work such as driving, watching TV, reading, etc. is okay as long as your vision is good and you don't get tired. Wear sunglasses outdoors for the first few weeks.
» Be careful not to rub your eyes during the first month.
» Avoid applying makeup to the eyelids and around the eyes for at least the first two weeks after surgery.
» Do not go to the pool for two to three weeks after surgery, and wear swimming goggles after that. Do not dive for at least three months after surgery. Do not.
» Dry eyes are common after LASIK, at least temporarily.
Recovery Period
It may take 3-6 months after surgery for your vision to stabilize.
» If your distance vision is corrected with LASIK, you may need glasses for reading around age 45.