Cataracts After RK: The Hardest Eyes to Calculate, and How We Do It

What RK did to the cornea

RK made four to sixteen deep radial incisions in the cornea, which flattened its center and reduced nearsightedness. The incisions never fully regain strength. The cornea is flatter than nature intended, often unevenly, and it tends to drift toward farsightedness over the decades, sometimes fluctuating during the day. Every one of those features makes measuring the cornea's true power difficult, and the lens calculation depends on that number.

Planning the surgery

• Corneal tomography maps the front and back surfaces, and repeated measurements on different days show how much the cornea varies
• Formulas designed for RK corneas are used, and several are compared rather than relying on one
• The cataract incisions are placed between the RK incisions, because cutting across an old RK cut can open it
• Intraoperative aberrometry can help, though it is less reliable in RK eyes than after LASIK because the cornea swells during surgery
• The Light Adjustable Lens is usually recommended: it lets the final power be set after the cornea has fully settled, which sidesteps the calculation problem

After surgery

RK corneas swell for longer than normal corneas after surgery, and the old incisions can gape slightly, so vision typically fluctuates for two to six weeks and may lean farsighted at first before settling. This is expected and is explained beforehand; glasses are not prescribed until the cornea is stable. With the Light Adjustable Lens, the adjustment visits begin only once this stability is confirmed, which is the whole point of choosing it.

Choosing a lens

Because RK corneas are irregular and often have higher order aberrations, multifocal lenses are generally avoided. A monofocal Light Adjustable Lens, sometimes with blended vision between the eyes, gives the most reliable result. Your surgeon will discuss what is realistic for your cornea.