Lasik eye surgery: Basic Guide to Eyesight Correction

Introduction:

Refractive surgery refers to correcting refractive errors (the errors that impair clear vision) in the eye. Laser-Assisted In Situ Keratomileusis (LASIK; LASER is light amplification by the stimulated emission of radiation) is a refractive surgery procedure that permanently alters the shape of the cornea (white of the eye). The United States Food and Drug Administration (US FDA) report shows that about 95 percent of patients are satisfied with their LASIK treatment. Refractive surgery has evolved beyond traditional LASIK surgery. In traditional LASIK, the surgeon used a blade to create a corneal flap. Although the method is safe, hand-held blade use has risks and complications. Refractive surgical eye implants have also been recently launched. However, the main reason for the popularity of advanced treatments is better postoperative results.

What Are the Refractive Errors Requiring LASIK?

Many refractive errors are a mismatch between the cornea optics, lens, and the length of the eye globe. LASIK corrects:

1. Nearsightedness (also called myopia; images focused in front of the retina)- Decreasing the corneal curvature by removing tissue from the center corrects myopia.

2. Farsightedness (also called hypermetropia; images formed behind the retina)- Increasing the corneal curvature by removing tissue from the periphery corrects hypermetropia.

3. Astigmatism (caused due to distortions on the corneal surface)- LASIK corrects astigmatism by removing variable amounts of corneal tissue at different points.

What Is the Procedure of LASIK Refractive Surgery?

In LASIK, a flap (contact lens size) is created using a special cutting laser (femtosecond laser). Subsequently, the flap is placed back in its original position. As a result, it attaches to the corneal surface itself.LASIK results in less pain, haze, and faster recovery. It further stabilizes the vision and is a better modality for advanced myopia.

Newer procedures include epithelial LASIK, femtosecond laser extraction, and small incision lenticule extraction (SMILE). The surface ablation procedure uses a laser to scrape eye epithelium (cell layer).

What Are the Patient Selection Criteria and Contraindications for Refractive Surgery?

The examination before surgery includes an estimation of the visual acuity (vision clarity) and a retinal (the eye area that helps one see) examination. The procedure requires dilation. Hence, the doctor may administer dilating eye drops. It results in blurred vision for at least three hours. So, it is best to come with a companion to drive back.

For better results, the power of the eyeglasses should not have changed for at least a year.

The most important part is a detailed scan of the cornea. Contact lenses must be discontinued about a week before the surgery for corneal surface stabilization. It is because it allows for accurate preoperative measurements. The surgical team is responsible for the preoperative evaluation, patient selection, and counseling.

The patient selection criteria are:

1. Patients must be 18 (preferably older) with stable vision for at least one year. It is because eyesight continues to change into adolescence.

The contraindications for refractive surgery are:

1. Pregnant and Lactating Women: Risk of myopia progression and hazy vision. Pregnant women have to avoid fetal exposure to medications (given after surgery). Further, refractive surgery is also not advised because the corneal curvature changes during pregnancy. It is expected and usually happens to around 50 percent of the patients.

2. Uncontrolled diabetes mellitus (DM): Diabetic patients have reduced nervous sensations in the eye. As a result, the procedure can lead to further dryness.

3. Thin Cornea: It can result in insufficient tissue after ablation. Further, it can result in a corneal breakdown.

4. Patients Younger Than 18: Refractive errors can progress after the procedure as the vision is unstable.

5. History of Herpes: Lasers may reactivate the herpes virus. LASIK can be done if the disease does not recur for one year. However, antiviral drugs should be used before the surgery.

Patients must have realistic expectations about the visual quality achieved with LASIK. For example, it may not match the clear and crisp vision with artificial contact lenses. Therefore, many patients require glasses or contact lenses after LASIK.

What Is the Success Rate of LASIK Refractive Surgery?

With current technology and appropriate patient selection, about 98 percent of patients achieve at least 20/40 visual acuity. It is adequate to pass a driver’s license eye test without glasses. Further, more than 90 percent obtain 20/20 visual acuity.

There is no complication-free surgery in the world. The latest modes of corneal imaging and scanning allow for a high degree of accuracy in obtaining the correct power. As a result, it leads to good outcomes. However, some complications include:

1. Dry Eye: About 40 percent of patients have dry eyes, burning, itching, and discomfort. These symptoms peak in intensity around three months after LASIK. However, they usually resolve after six to 12 months. The cause of dry eye symptoms varies among patients. Studies suggest LASIK interrupts the sensation of the cornea, reducing the stimulus to tear production. However, these effects are temporary. Approximately 20 percent of patients have persistent dry eyes. Dry eyes can be corrected with artificial tears and cyclosporine eye drops.

2. Visual Symptoms: Various visual symptoms, such as glare, halos, starbursts, and reduced contrast, can affect up to 20 percent of patients. These symptoms are bothersome during night driving.

3. Diffuse Lamellar Keratitis (DLK): It is corneal inflammation that occurs after LASIK. It occurs in 2 to 4 percent of patients undergoing LASIK. DLK occurs within the first week post-surgery. DLK involves cellular disruption and incorporation of debris at the edge of the operative area. DLK is treated with topical or systemic corticosteroids.

4. Others: Epithelial ingrowth (cells get trapped under the corneal flap), flap wrinkles, and bacterial and fungal infections are other potential complications.

LASIK is the most popular form of refractive error correction. But, other procedures such as Epi-LASIK (an advanced LASIK procedure) may be more suitable for patients at risk of flap dislodgement. Epi-LASIK opens a thinner flap and is suitable for persons with thin corneas.

Further, patients should have reasonable expectations and cooperate with the surgeon to find the best approach to vision correction. Most patients report satisfaction with LASIK. Still, some patients have different satisfaction levels with similar vision correction. On the other hand, some individuals may be less tolerant of the surgery due to discomfort and inconvenience.

Conclusion:

To conclude, the field of refractive surgery is rapidly evolving with many options to correct refractive errors. Rapid advances in technology have increased refractive surgical options available to patients. Hence, with the emerging trends, eye surgeons must be aware of the advantages and disadvantages while emphasizing careful patient selection.