Long-Term Effects of Radial Keratotomy: What Surgeons Should Know

Radial keratotomy (RK) was once a revolutionary refractive surgery technique used primarily to correct myopia (nearsightedness). Developed in the 1970s by Russian ophthalmologist Svyatoslav Fyodorov, RK gained widespread popularity in the 1980s and early 1990s before being largely supplanted by more advanced techniques like LASIK and PRK. Despite its decline in popularity, RK remains an important topic in ophthalmic surgery, particularly in understanding its long-term effects, complications, and the management of patients who underwent the procedure.

This comprehensive guide will delve into the indications, preoperative evaluation, contraindications, surgical techniques, postoperative care, possible complications, different RK techniques, prognosis and outcome, alternative options, average cost, recent advances, and more.

Indications for Radial Keratotomy

Radial keratotomy was primarily indicated for the correction of mild to moderate myopia. The procedure was most effective for patients with low to moderate levels of nearsightedness, typically between -1.00 and -4.00 diopters. Additionally, RK was occasionally used for the correction of astigmatism by altering the incision pattern.

Ideal candidates for RK included:

• Stable Myopia: Patients with stable myopia for at least one year.
• Thin Corneas: Patients with relatively thin corneas, where other refractive surgeries like LASIK might be less suitable.
• Low to Moderate Myopia: Patients with myopia in the range of -1.00 to -4.00 diopters.
• Desire to Eliminate Glasses or Contact Lenses: Individuals seeking to reduce or eliminate their dependence on corrective lenses.

Preoperative Evaluation

Before performing RK, a thorough preoperative evaluation was essential to determine patient suitability and predict outcomes. The evaluation process typically included:

1. Detailed Patient History: Assessing the patient’s ocular and general medical history, including previous refractive surgeries, ocular diseases, and systemic conditions that might affect healing.
2. Refractive Stability: Ensuring refractive stability for at least 12 months to avoid post-surgical refractive regression.
3. Corneal Thickness Measurement: Pachymetry was used to measure corneal thickness, as patients with very thin corneas were poor candidates for RK.
4. Keratometry: Measuring corneal curvature to plan the surgical incisions accurately.
5. Topography: Corneal topography provided detailed mapping of the cornea’s surface, helping to identify irregularities or conditions like keratoconus.
6. Visual Acuity Testing: Establishing baseline visual acuity to measure postoperative improvements.
7. Pupil Size Assessment: Larger pupils were associated with increased risk of night vision disturbances post-surgery.
8. Informed Consent: Discussing the potential risks, benefits, and alternatives with the patient to ensure they had realistic expectations.

Contraindications

Several contraindications existed for radial keratotomy, which included:

• Unstable Myopia: Patients with progressive myopia were not suitable candidates due to the risk of postoperative regression.
• Keratoconus: The presence of keratoconus or other ectatic disorders made RK highly contraindicated due to the risk of exacerbating corneal thinning.
• Systemic Conditions: Autoimmune diseases, diabetes, or other conditions that could impair wound healing were contraindications.
• Corneal Scarring: Pre-existing corneal scars could interfere with the RK procedure and lead to unpredictable results.
• Thin Corneas: Corneas below a certain thickness were at risk for perforation or excessive weakening post-RK.
• Large Pupils: Patients with large pupils were at higher risk for visual disturbances, such as halos and glare, particularly at night.
• High Myopia: RK was less effective and riskier for patients with high myopia (greater than -6.00 diopters).

Surgical Techniques and Steps

Radial keratotomy involved making a series of radial incisions in the cornea to flatten its curvature and reduce myopia. The key steps in the procedure were as follows:

1. Anesthesia: Topical anesthesia was typically used, although some surgeons opted for a combination of topical and mild sedative.
2. Marking the Cornea: The cornea was marked with a specialized instrument to guide the placement and depth of the incisions.
3. Incision Planning: The number and depth of incisions were determined based on the degree of myopia, corneal thickness, and patient-specific factors. Typically, 4 to 8 radial incisions were made, extending from the periphery toward the center but stopping short of the visual axis.
4. Making the Incisions: A diamond knife with adjustable depth settings was used to create the radial incisions. The depth was usually set at around 90% of the corneal thickness.
5. Postoperative Care: After the procedure, the patient was prescribed antibiotics and anti-inflammatory drops to prevent infection and control inflammation. The eye was typically patched for a few hours, and patients were advised to rest.

Postoperative Care

Postoperative care following radial keratotomy was crucial for optimal outcomes. The main aspects included:

• Medications: Patients were prescribed antibiotic eye drops for about a week and anti-inflammatory drops for several weeks to reduce the risk of infection and control inflammation.
• Follow-Up Visits: Regular follow-up visits were essential to monitor healing, check for complications, and assess refractive stability.
• Activity Restrictions: Patients were advised to avoid strenuous activities, rubbing their eyes, and swimming for several weeks post-surgery.
• Monitoring for Complications: Close monitoring was required to detect any signs of complications, such as infection, overcorrection, undercorrection, or progressive flattening of the cornea.

Possible Complications

While RK was effective in many cases, it carried a range of potential complications, including:

• Infection: Although rare, infection could occur, leading to keratitis and potentially severe corneal damage.
• Overcorrection/Undercorrection: The most common complications were refractive in nature, with some patients experiencing overcorrection (leading to hyperopia) or undercorrection (persistent myopia).
• Irregular Astigmatism: The incisions could sometimes heal unevenly, resulting in irregular astigmatism and distorted vision.
• Diurnal Fluctuations: Many patients experienced fluctuations in their vision throughout the day, with better vision in the morning and worsening as the day progressed.
• Progressive Flattening: In some cases, the cornea continued to flatten over time, leading to a progressive shift toward hyperopia.
• Scarring: Corneal scarring at the incision sites could lead to permanent vision changes and potential visual disturbances.
• Night Vision Problems: Halos, glare, and starbursts around lights at night were common, particularly in patients with larger pupils.
• Corneal Perforation: A rare but serious complication where the incisions penetrated too deeply, potentially leading to corneal perforation.

Different Techniques of Radial Keratotomy

Over the years, several variations of the standard RK procedure were developed to improve outcomes and reduce complications:

• Mini-RK: This technique involved making fewer incisions, typically only 4, rather than the standard 8. It was used for mild myopia and aimed to reduce the risk of overcorrection and other complications.
• Asymmetric RK: This approach was used for correcting astigmatism by making asymmetrical incisions that targeted the steeper meridian of the cornea.
• Tissue-Saving RK: Aimed at minimizing the amount of corneal tissue disrupted, this technique involved making shallower or shorter incisions, thereby reducing the risk of complications like progressive flattening.

Prognosis and Outcome

The long-term outcomes of RK varied significantly among patients. While many patients achieved satisfactory vision correction initially, the long-term stability of these outcomes was less predictable. Key factors influencing prognosis included:

• Degree of Myopia Corrected: Patients with lower degrees of myopia generally experienced more stable and predictable outcomes.
• Corneal Healing: The way each patient’s cornea healed played a crucial role in the final visual outcome, with some developing irregular astigmatism or scarring.
• Age: Younger patients were more likely to experience progressive hyperopia due to continued flattening of the cornea over time.
• Refractive Stability: While many patients enjoyed several years of improved vision, some experienced a gradual return of myopia or a shift toward hyperopia over time.

Alternative Options

With the advent of more advanced refractive surgery techniques, RK is now rarely performed. Alternative procedures include:

• LASIK (Laser-Assisted In Situ Keratomileusis): LASIK has largely replaced RK as the preferred method for correcting myopia. It involves creating a corneal flap and reshaping the underlying tissue with an excimer laser.
• PRK (Photorefractive Keratectomy): PRK is similar to LASIK but does not involve creating a flap. Instead, the surface layer of the cornea is removed, and the underlying tissue is reshaped with a laser.
• LASEK (Laser-Assisted Sub-Epithelial Keratectomy): LASEK is a variation of PRK where the epithelial layer is preserved and repositioned after laser treatment.
• SMILE (Small Incision Lenticule Extraction): SMILE is a minimally invasive procedure where a small piece of corneal tissue is removed through a small incision to reshape the cornea.

Average Cost

The cost of RK in its heyday varied depending on the surgeon's experience, location, and the specifics of the procedure. On average, the cost ranged from $1,000 to $2,500 per eye. Today, RK is rarely performed, and the cost of managing complications or undergoing corrective procedures like LASIK can be significantly higher.

Recent Advances

While RK is largely considered obsolete, its historical importance in the evolution of refractive surgery cannot be overstated. Modern advancements focus on refining laser-based techniques like LASIK, PRK, and SMILE, which offer greater precision, faster recovery times, and more predictable outcomes. Additionally, there is ongoing research into managing long-term complications of RK, such as progressive hyperopia and irregular astigmatism, using modern techniques.