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Presbyopia treatment in 2017: Where are we?
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Looking at the present state of refractive surgery, in which the correction of refractive errors such as myopia, hyperopia and astigmatism has become safe, accurate and precise with outstanding results for most patients, I feel that presbyopia correction still involves challenges and compromises. Think of the procedures we use to correct, let’s say, 2 D of myopia. I can count three, maybe four, surgical techniques that are currently used — LASIK, PRK, advanced surface ablation, SMILE — and all of them provide similar, excellent results. Think now of the procedures we use to correct the same amount of presbyopia, 2 D. I can count at least 10 different approaches, and none of them gives the same results. This, however, does not mean that presbyopia cannot be safely and successfully corrected. It means that each single approach has potential advantages but also downsides leading to compromises, and our challenge as surgeons is to identify for each single patient what is the best acceptable combination between advantages and compromises.
The cover story in this issue of Ocular Surgery News presents a round table on presbyopia correction, which gives me the opportunity to focus on the current and future approaches to treat presbyopia without removing the crystalline lens and implanting a multifocal IOL, which, in my opinion, represents the best option today.
Let’s start from monovision (one eye plano, the other one –1.5 D). It can be obtained through several different surgical procedures, although it is commonly delivered with laser treatments. It is extremely safe, and it can be reversed, even with spectacles. These are the greatest advantages. On the other hand, it works better in younger patients, and it is monovision. This means that the two eyes perform differently, with some loss of stereoacuity, which is not what patients would like to have should a better option be available. Spectacle independence relies also on the eye’s residual accommodation, being better performing in younger patients than older patients.
PresbyLASIK is another option. There are several approaches to correct presbyopia through laser ablation, as branded and marketed by the different laser companies. The basic principle is quite similar, though. The target is to create a multifocal cornea able to increase depth of focus. With most approaches, the treatment involves both eyes, in which one eye gets better distance vision and the other one is more focused for near. Compared with monovision, PresbyLASIK improves binocular functions, both for distance and near in a sort of blended vision between the two eyes, and stereoacuity is less compromised. It is a safe procedure, and it is claimed to be reversible with a second laser treatment (but not with spectacles), although the number of reversal procedures performed is not wide enough to take it for granted. Eyes may experience some best corrected visual acuity loss and night vision symptoms such as halos and glare.
Corneal inlays have been around for a while, especially in Europe, and now that the FDA has approved two of them, they are generating increasing interest. There are three main inlays in the market, and they perform through different principles. The Kamra (AcuFocus) provides increased depth of focus thanks to a pinhole effect. The Raindrop (ReVision Optics) alters the eye’s refractive power by increasing the central radius of curvature of the part of the cornea overlaying the implant. The Flexivue Microlens (Presbia) has a plano central area to provide distance vision, surrounded by rings with different add powers for intermediate and near vision. All of them are aimed to be implanted in the non-dominant eye. They provide good spectacle independence and are removable, but that does not mean reversibility in 100% of cases. Again, side effects are loss of BCVA lines and night vision symptoms.
Scleral procedures also have a relatively long history. While scleral relaxing incisions have been almost completely abandoned, scleral implants are still performed. The hypothesized mechanism of action of the Refocus VisAbility is a retensioning of the posterior zonule, giving the ciliary muscles more efficiency in reshaping the lens. This surgery is a little bit demanding, but it has potential advantages such as being off the visual axis (unlike all other techniques), thus leading to fewer changes in distance vision and night vision problems. However, the efficacy and stability still have to be determined.
In conclusion, we have several procedures to help our patients become less spectacle dependent for intermediate and near, but none of them looks like the ultimate one yet. There are also some recent novel noninvasive approaches to treat presbyopia that look promising. Electrostimulation of the ciliary muscle seems to help delay presbyopia at least in younger patients. Some pharmacologic approaches have shown early encouraging results. Recent research shows that drops can be instilled in the eye either to induce miosis without accommodation with pinhole effect or to increase crystalline lens flexibility and restore elasticity. Hopefully in 2017 we will get some better understanding on these methods.
- For more information:
- Francesco Carones, MD, can be reached at Centro Oftalmico Chirurgico Carones, Via Pietro Mascagni 20, 20122 Milano, Italy; email: fcarones@carones.it.
Disclosure: Carones reports he is a consultant for AcuFocus, Alcon, Abbott Medical Optics and WaveLight.