Cataract after
radial keratotomy

Radial keratotomy, briefly

Radial keratotomy was a myopia-correction technique used before the arrival of the laser. The principle: make incisions arranged like the spokes of a wheel to deliberately weaken the periphery of the cornea and flatten its centre, thereby reducing myopia.

Effective for its time, this technique was largely abandoned with the arrival of the laser, which is more precise and more stable. But tens of thousands of patients still carry its incisions. And this is an essential point to understand: these incisions never disappear. They remain etched in the cornea as permanent lines of weakness, decades after the procedure.

Why the surgical step must be adapted

Cataract surgery requires a small incision to reach the lens and replace it with an implant. In a normal eye, this incision is usually made in the cornea itself, at the periphery.

In a cornea bearing radial incisions, this standard approach poses a problem: the cataract-surgery incision could cross or reopen the old keratotomy incisions, which remain areas of weakness. Such a reopening can lead to refractive instability, unpredictable healing, or even an intraoperative complication.

My approach in this context is to adapt the incision: I favour a scleral incision, made in the white of the eye, sturdier and deliberately kept away from the radial incisions of the cornea. This approach avoids stressing the existing lines of weakness and makes the procedure safer. It is a simple change in principle, but a decisive one for the safety of the step in these patients.

Calculating the implant: even more complex than after laser

Any previous refractive surgery complicates the implant calculation. Radial keratotomy pushes this difficulty a step further.

Where the laser modifies the cornea in a controlled and relatively uniform way, radial keratotomy modifies it in a more irregular and less predictable manner. Several factors add up: corneal power can fluctuate over the course of the day — an incised cornea is not perfectly stable — healing varies considerably from one patient to another, and the geometry of the central zone is difficult to measure precisely.

Standard biometric formulas are completely unsuited to these corneas. Specific formulas, developed for eyes with radial keratotomy (ASCRS Post-RK, an adapted Barrett True-K), are essential. And even with these tools, I prefer to be honest: the margin of uncertainty remains higher than in any other cataract-surgery situation. This is a reality I explain systematically before the procedure, because it is part of an informed decision.

Choosing the implant: a decision guided by corneal aberrations

Radial incisions do not only degrade the regularity of the cornea: they create what are known as higher-order aberrations. These are optical imperfections that go beyond simple myopia or astigmatism — they disturb image quality by scattering light, and cannot be corrected with ordinary spectacles. The choice of implant must take them into account directly.

My approach is graded according to the extent of these aberrations.

When the higher-order aberrations are mild to moderate, I usually offer an EDOF implant (extended depth of focus). Its optics tolerate small corneal irregularities well: they smooth out visual variations and optimise depth of focus, giving more stable and more comfortable vision than a standard implant would offer on such a cornea.

When the aberrations are high, I offer a small-aperture implant, the IC-8. Its principle is that of the pinhole — the same as the small hole that makes an image sharper when you look through it. By filtering out the peripheral light rays, which are precisely those most disturbed by the radial incisions, the IC-8 implant clearly improves image quality despite the irregularity of the cornea. It is a particularly well-suited solution for these complex eyes, where conventional implants reach their limits.

This logic is not a catalogue of options: it is an adaptation to the real optical profile of your eye, determined by the measurements from the assessment.

What this changes for you in practice

Several practical consequences follow from this complexity.

The preoperative assessment is longer and more thorough, and some measurements may be repeated at different times to account for the fluctuations of your cornea.

Expectations deserve to be calibrated carefully. The realistic goal is a significant improvement in your vision and good image quality — not necessarily perfect spectacle independence. On a cornea bearing radial keratotomy, aiming for refractive perfection would be a promise no one could honestly keep.

Finally, visual recovery may be a little more gradual, and some fluctuation of vision in the first few weeks is possible. This is part of the expected course for these particular eyes.

Recovering your records

As with any previous refractive surgery, the documents from your original keratotomy — operative reports, prescriptions before the procedure — can help with the implant calculation. In the case of radial keratotomy, however, these documents are rarely available: the procedure often dates back thirty or forty years.

Their absence is not an obstacle. The detailed topographic analysis of your current cornea then becomes the main basis for the calculation, complemented by the specific formulas mentioned above.

In consultation

In this context, the assessment rests on detailed corneal topography — essential here to map the irregularities and measure the higher-order aberrations — high-precision biometry, a complete examination of the retina and macula, and an in-depth discussion of your history and goals.

This is a specialised consultation that takes the time it needs. The complexity of these eyes fully justifies this investment upfront: it is what determines the quality and safety of the result.