Ametropia after Refractive Lens Exchange

Treat the patient, not the refractive error. Cheryl Guttman Krader reports from the 39th Congress of the ESCRS in Amsterdam

Surgeons need to be aware that a refractive surprise can occur in an appreciable percentage of cases of refractive lens exchange and residual refractive error is the primary reason for patient dissatisfaction after premium IOL surgery.

As good news, a refractive surprise can be managed with excellent results in most patients, said Nic J Reus MD, PhD.

Speaking at the ESCRS Congress about managing ametropia after refractive lens exchange, Dr Reus discussed identifying the cause and corrective options. He said avoiding patient dissatisfaction because of a refractive surprise, however, begins with appropriate preoperative counselling.

“How many refractive surprises you encounter in practice depends on how you managed patient expectations before surgery. Suggesting to patients with high ametropia the surgery will reduce the refractive error is very different from saying they will be completely spectacle independent,” Dr Reus emphasised.

“We also have to recognise and take into account in our preoperative counselling that the refractive outcome will not be within 1 D of target in perhaps 5% of patients, and we cannot achieve perfect reduction in astigmatism with toric IOLs in all patients.”

ANALYSING THE CAUSE Before planning any intervention for a refractive surprise, surgeons should wait at least six weeks for the refraction to stabilise after the primary surgery. Then, a meticulously performed complete ophthalmic examination—including manifest refraction, slit-lamp exam, corneal topography, and biometry—is needed to understand the cause.

“I often retake the keratometry measurement myself with a Javal keratometer. [Bear in mind] getting the most plus refraction is especially important in eyes implanted with the newer monofocal plus, extended depth of focus, and trifocal IOLs. Although you probably did a careful slit-lamp examination preoperatively, you may have missed some preexisting pathology, or there may be capsular fibrosis, ophthalmic viscosurgical device behind the IOL, or cystoid macular oedema,” Dr Reus observed.

Check IOL power by comparing the power of the implanted lens with the intended power and by reviewing the biometric data used for the calculations. Dr Reus suggested using optimised and even personalised lens constants and choosing the right formula could minimise power calculation errors.

“Personally, I like to use the Barrett Universal II and Barrett Toric formulas that include the posterior corneal astigmatism,” he said. REVIEWING MANAGEMENT OPTIONS Correcting residual ametropia with spectacles or contact lenses is always a viable option, even though most patients do not hope for this outcome when choosing refractive lens exchange.

In eyes with a toric IOL and residual astigmatism, rotating the lens may correct the problem. Surgeons can plan the procedure using online tools such as www.astigmatismfix.com or with the Barrett Rx formula at www.apacrs.org.

Surgeons can also consider excimer laser enhancement, but an ASCRS paper advised using this approach only to correct spherical errors ≤1.0 D. IOL exchange can be done in cases with larger refractive errors and hyperopic errors, but carries risks of posterior capsule rupture, corneal oedema, and surgically induced astigmatism because of its larger incision. Options for power calculations in IOL exchange include refractive vergence formula, Holladay R formula, or Barret Rx formula.

Sulcus placement of an add-on IOL is another option that is technically relatively easy, very predictable, and done through a smaller incision. With this approach or any surgical correction, patients need to be informed the procedure may exacerbate ocular surface disease and bothersome dry eye symptoms, Dr Reus said.

If performing the bilateral refractive lens exchange sequentially rather than simultaneously and a refractive surprise appears in the first eye, the error can be taken into account by adjusting the IOL power when treating the fellow eye. In this situation, the second IOL power should be between 30% and 50% of the prediction error, he explained.

PEARLS FOR PATIENT COUNSELLING A refractive surprise may not be the surgeon’s fault, given the unknowns accompanying the surgery, including effective lens position. Nevertheless, Dr Reus advocated offering patients an apology while explaining the reason for the outcome.

Management discussions should include the various options, the possible complications, and the pros and cons of treating the refractive surprise.

“Please explain any spectacle dependency. For example, patients who had a trifocal IOL and want it exchanged for a monofocal IOL because of bothersome dysphotopsia may not realise they will no longer be able to read without glasses,” Dr Reus said.

“Or, if patients have halos at night because of residual myopia after monofocal IOL surgery, they need to know they might lose their ability to read without correction after a refractive enhancement.”

Dr Reus concluded his presentation with sound advice: “Treat the patient, not the refractive error. It can be that you are more unhappy than the patient.”

“How many refractive surprises you encounter in practice depends on how you managed patient expectations before surgery.”

Nic J Reus MD, PhD is in the Department of Ophthalmology, Amphia Hospital, Breda, the Netherlands. nreus@amphia.nl