Conventional IOL still often best choice for presbyopia correction

In a “Back to the Future” moment, a presbyopia-correction patient from 1985 pays a visit and brings a new prospective patient.

Recently I had a remarkable reunion with one of my cataract patients. Ed reminded me that on November 5, 1985, I had told him he became my seventh patient to undergo presbyopia correction using the conventional IOL approach.

Ed knew every detail of the procedure because he had kept all of his meticulous notes on our preop presbyopia discussions. He recited the details of his astigmatism correction and the precise amount of myopic defocus I had calculated for the accommodative effect we were seeking. He brought me a copy of the 11-minute videotape of his procedure. He even had the old Iolab ID card for each implant.

Coming now when we are so intently focused on evaluating the relative merits of three new presbyopia-correcting IOLs, this unexpected visit from one of my earliest presbyopia corrections was something of a time warp – a true “Back to the Future” moment. Checking and rechecking the dates on those ID cards, I just could not believe that it was really 20 years ago.

Surgical encore

Ed had returned because his wife, Maxine, was ready for cataract surgery. Naturally enough, she wanted the same presbyopia-correcting result. Ed still reads fine print with fluid ease and proudly assures me that since the day after his second eye was done he has “never used a pair of glasses again.”

William F. Maloney

Although he far exceeded my cautious expectations at the time, Ed was so completely satisfied for one fairly straightforward reason. In each eye, we managed to hit exactly the refractive power that was targeted specifically for him. Although a fair bit of luck was involved 20 years ago, today this degree of refractive accuracy is increasingly within our technology-stretched reach.

He brought his file with him to help ensure that Maxine received the same tailor-made reading result.

“But Ed,” I said, “we now have new IOL technologies to consider. There are three new implants, each specifically designed to deliver reading vision without glasses.”

I outlined what I saw as the relative merits and limitations of the eyeonics crystalens, the Advanced Medical Optics ReZoom and the Alcon ReSTOR as Maxine listened and Ed again took to his notes.

IOLs for presbyopia: real world comparison

In Maxine’s case, the inevitable “specific comparison syndrome” presented some significant challenges for each of the new presbyopia-correcting IOLs. Here are a few specifics of her real world comparison.

Versatile approach: conventional IOLs

Not surprisingly, we chose the conventional IOL approach for Maxine’s presbyopia correction. I have previously detailed the approach using conventional IOLs for presbyopia correction in this column. (See “Conventional lens implants provide versatile approach to presbyopia correction,” September 2006.)

A conventional IOL is one of the choices for correction of presbyopia. Image: Maloney WF

Important factors in this decision included avoiding a relatively unfavorable comparison with Ed’s particular result and her understandable confidence in having the same approach. However, her specific near focus goals of both fine print reading and complete intermediate focus made the versatility of the conventional IOL pairing a prime consideration.

Another important factor was our comparison of the specific compromise inherent in each IOL. In this instance it pointed to the conventional IOL approach as the clear best choice. Here’s why.

We tested against her proposed target of –0.38 D for her distance eye and –1.93 D for her near eye. Together with the 1 D of pseudoaccommodation inherent in any conventional implant, this particular IOL pairing provided both the 3 D of accommodative effect she needed for full fine-print reading and a range of smoothly blended intermediate and distance focus to meet her other goals.

She fully expected to need glasses for night driving, the movie theater and possibly day driving – for her, an acceptable compromise. She recently told me that she has not needed glasses for any of these activities. This is typical of cataract-age patients who usually drive only locally at night and have relatively small scotopic pupils. Nevertheless, it is always helpful to factor in an opportunity to exceed expectations.

Suppression strength a key indicator of acceptance

Her preop defocus tolerance and her strength of dominance/suppression testing clearly told me that she could easily suppress, and thus automatically adapt, within hours, not months, to the 1.55 D of interocular myopic defocus in this IOL pairing. We also had the comfort of knowing that statistically more than 80% of our previous candidates have automatically accepted this degree of interocular myopic defocus.

In her case, the IOL choice was clear. We had identified the specific pair of conventional IOLs that we knew with a high degree of confidence would be readily accepted and deliver the full range of her particular reading goals. She fully understood and anticipated the companion compromises. This is the formula for consistent success with presbyopia correction. Yet this is not to say that every factor in this equation was now fixed and the outcome certain.

Refractive accuracy the vital surgical skill

The remaining uncertainty lies in actually implanting the exact IOL power targeted for each eye – still a challenge to be sure, but a variable that we can almost fully control with today’s techniques. State-of-the-art biometry is crucial, which in my view means that you, the surgeon, not a technician, should be skillfully using the Carl Zeiss Meditec IOLMaster. It also means precise astigmatic correction for any amount of cylinder above 0.75 D, usually using peripheral AK.

And lastly, it requires that our partners in industry finally move to update IOL power labeling to include the actual measured power. As I have written here before (see “IOL parameters no longer pass the accuracy test,” September 2005 issue), the present error range bracketing the labeled IOL power is an anachronism that introduces an increasingly untenable risk to all surgeons – not just those correcting presbyopia – of a clinically significant refractive surprise.

Can you quantify the compromise?

How a candidate will respond and adapt to the compromise inherent in each of the three new presbyopia-correcting IOL technologies is a relative unknown that still makes me uneasy.

As we just saw, we can reliably measure the interocular defocus tolerance that we need to know for a successful conventional IOL approach. (See “Presbyopia success depends on comprehensive preop evaluation,” August 1 issue.) We cannot, however, quantify each candidate’s neural adaptability to bilateral multifocal blur; there is no objective preop assessment. Nor can we predict where the crystalens will finally position itself within the capsular bag, and thus we cannot target a given reading result with the same level of confidence.

Obviously these are relative issues and clearly do not preclude the use of these new presbyopia implants. Nonetheless, these are important considerations when we attempt to answer the central question for successful presbyopia correction, “Which IOL is best for this patient?”

The reunion with Ed highlighted for me just how long a track record the conventional IOL has in correcting presbyopia. I would not be surprised if more presbyopia corrections have used conventional IOLs than the three newer presbyopia implants combined.

Maxine’s recent result tells us that the versatility of each unique IOL pairing and – assuming careful comprehensive preop testing – the lack of uncontrollable variables makes the conventional IOL still a strong contender today.

Just as with each of the other three presbyopia implants, the conventional IOL does not top the list for every candidate. There are some candidates for whom each one of the newer alternatives will be a better choice. However, the conventional lens approach remains the clear best choice for many patients, especially cataract patients such as Ed and Maxine, who seek both intermediate and full fine print reading capability – “real reading,” as Ed calls it when he proudly compares his result with other patients in our waiting room.

Next column

Six steps to presbyopia correction with conventional IOL.

For more information:

• William F. Maloney, MD, can be reached at 2023 West Vista Way, Suite A, Vista, CA 92083 U.S.A.; +1-760-941-1400; fax: +1-760-941-9643; e-mail: maloneyeye@yahoo.com. Dr. Maloney has no financial interest in any ophthalmic product and has no financial relationship with any ophthalmic company.

• Lens-based Refractive Surgery Column Mission Statement: To educate readers on all aspects of lens implant refractive surgery including presbyopia correction, refractive cataract surgery, refractive lens exchange and phakic IOLs.