Radial Keratotomy RK

Radial Keratotomy

Radial keratotomy was a surgical technique used primarily in the 1970s and 1990s to correct mild to moderate myopia (up to -6 diopters). It involved making radial cuts in the cornea with a diamond knife, weakening its central curvature to flatten it and reduce refractive error.

Key Features:

Invasive procedure: No laser, with risks of corneal irregularities.

Unpredictable results: Could cause irregular astigmatism or night halos.

Discontinued: Replaced by safer techniques such as LASIK, PRK, and SMILE.

Is it used today?

❌ No, except in exceptional cases of specific corneal scarring.

Difficulties in Intraocular Lens (IOL) Calculation for Patients Undergoing Radial Keratotomy (RK)

Radial keratotomy (RK) was a popular technique in the 1980s and 1990s for correcting myopia through radial corneal incisions. Today, many of these patients develop cataracts and require IOL implantation, but calculating the lens power is complex due to the corneal alterations left by RK.

Problems in IOL Calculation

1. Altered Corneal Curvature

RK incisions generate irregular central flattening, which distorts measurements of:

Keratometry (K).

Corneal topography.

Traditional formulas (SRK/T, Hoffer Q, Holladay) fail because they assume a spherical cornea.

2. Non-Standard Corneal Refractive Index

RK changes the relationship between the anterior and posterior curvature of the cornea, affecting the dioptric power calculation.

3. Unknown Surgical History

Many patients do not remember how many incisions were made or their depth, making planning difficult.

Methods to Improve Accuracy

1. Specialized Formulas

Haigis-L: Less reliant on keratometry.

True-K (Wang-Koch): Adjusted for post-RK corneas.

Barrett True-K formula: Currently the most accurate.

2. Measurement with Advanced Devices

Corneal topography (Pentacam, Galilei) to assess irregularities.

OCT biometry (Lenstar, IOLMaster 700) to measure axial length more accurately.

3. Complementary Techniques

Therapeutic contact lenses to simulate previous refractive correction.

High-frequency ultrasound if corneal opacities are present.

40% of post-RK patients require postoperative adjustments (such as glasses or special contact lenses) due to calculation errors..

Types of Intraocular Lenses (IOLs) Recommended for Patients with a History of Radial Keratotomy

1. Monofocal IOL

Advantage: Less optical distortion in irregular corneas.

Disadvantage: Need for glasses for near and far vision.

2. Toric IOL

Only if the astigmatism is regular and measurable.

Risk: Difficult alignment due to corneal irregularities.

3. Extended Range IOL (EDOF)

Option if greater independence from glasses is desired.

Caution: May increase halos in irregular corneas.

4. Phakic IOL (ICL)

Alternative if the cornea is very irregular but the lens is still clear.

Are Multifocal Intraocular Lenses (IOLs) Recommended for Patients with Radial Keratotomy (RK)?

In general, multifocal IOLs are NOT the first choice for patients undergoing radial keratotomy (RK) due to the corneal alterations caused by this surgery. However, in selected cases and with a thorough evaluation, they may be considered.

Problems with Multifocal IOLs in Post-RK Patients

1. Irregular Cornea and Optical Aberrations

RK causes irregular corneal flattening, which distorts light as it passes through.

Multifocal IOLs depend on a well-centered and symmetrical cornea to function properly.

Risks: Blurred vision, halos, glare, and poor visual quality.

2. Difficulty Calculating the IOL

Traditional formulas fail in post-RK corneas (they underestimate or overestimate the power). Even with special formulas (Barrett True-K, Haigis-L), the prediction is less accurate.

3. Greater Sensitivity to Visual Effects

Post-RK patients are already often more sensitive to distortions (due to radial scarring).

Multifocal IOLs can aggravate these symptoms, causing dissatisfaction.

In What Cases Might a Multifocal IOL Be Considered in a Patient with a History of Radiation Keratotomy?

Although not ideal, in very controlled situations, a multifocal IOL could be evaluated if:

The cornea has a relatively stable topography (without extreme irregularities).

The patient understands the risks (possible halos, occasional need for glasses).

A newer-generation IOL is used (e.g., an extended-range trifocal, such as the AcrySof IQ PanOptix).

A calculation is performed using advanced formulas (OCT, corneal topography, and contact lens simulation).

What are the Best Alternatives for Patients with a History of Radial Keratotomy?

1. Monofocal IOL + Glasses

Advantage: Maximum visual quality for distance (far or near).

Ideal if the cornea is very irregular.

2. Toric IOL (if there is regular astigmatism)

Corrects astigmatism without introducing additional distortions.

3. Extended Range IOL (EDOF)

Offers intermediate and distance vision with fewer halos than multifocals.

Example: Tecnis Symfony.

4. Phakic Lens (ICL) if the lens is still transparent.

Does not alter the cornea and is reversible.