When Charles D. Kelman, MD, introduced phacoemulsification in 1967, it marked the most significant change in the modern era of cataract surgery. Phaco ushered in an era of smaller wounds and, soon after that, lens replacement technology. Sir Harold Ridley, FRCS, started it all with his observations of World War II fighter pilots. He got the idea for an artificial lens when he realized that shattered fragments from Plexiglas airplane windshields did not always lead to damage when they were lodged in the eye. Ridley subsequently conceived the first artificial lens, made of the same material as those windshields—PMMA.
As incision size continued to shrink, lens materials have changed. The type and variety of optical powers has evolved. The introduction of aspheric lens technology allowed the correction of focal length and higher-order aberrations. Monofocal IOLs account for most of the lenses implanted in the United States.
Monofocal IOLs, then, are a solution to cataract surgery. And although they may be right for some patients, they often fail to address other patient concerns.
Increasingly, the goal for cataract patients is to correct their presbyopia and restore both distance and near vision. Some multifocal IOLs that use concentric rings to provide multiple focal points have been associated with unwanted optical disturbances and glare concerns. This is mainly an issue with older high power–add multifocal IOLs and this has led to their limited adoption. These IOLs can also be contraindicated in patients who have optic nerve conditions, previous refractive surgery, retinal disease, and other conditions that might limit the outcome.
INTERMEDIATE AND DISTANCE VISION
Accommodating IOL technology uses the eye’s ciliary muscle to focus the implant without splitting the light, as multifocal IOLs do. This allows these lenses to provide good distance and intermediate vision. This modality is well suited to patients with no tolerance for glare and halos who want to emphasize their intermediate and distance vision.
Toric IOLs can be used to correct cylinder error at the time of cataract surgery, providing excellent outcomes and decreased dependence on glasses or contact lenses for distance vision in patients with astigmatism. Until toric IOLs were released, many patients with astigmatism were forced to wear glasses after cataract surgery at all times to see clearly.
IOLs with extended depth of focus (EDOF), such as the Tecnis Symfony (Johnson & Johnson Vision), do not depend on splitting light to improve the range of vision. EDOF IOLs smooth out the dips in the defocus curve, creating one elongated focal point.
Many cataract patients have had previous refractive surgery—LASIK or even radial keratotomy. With new IOL technology, surgeons can now customize postoperative vision by treating the patient’s spherical aberration. Traditionally, these individuals would have had to receive monofocal implants, as multifocal technologies would be contraindicated. Although use of the Symfony would be off-label in patients with previous refractive surgery, the lens tends to be more forgiving because of its broader “sweet spot,” and it may be a better choice in these situations. This IOL has become the go-to IOL for surgeons in my practice in part because it is more forgiving and requires less chair time. Less chair time is a win for patients, surgeons, and optometrists participating in the comanagement process.
In my experience, residual refractive error with multifocal IOLs limited outcomes and decreased patient satisfaction. I believe this was usually due to untreated ocular surface disease. The Symfony is more forgiving with residual refractive error.
The marketplace is populated by different patients with various conditions and desires; so too is it populated with IOLs that address different needs. High-level surgeons seeking to treat spherical aberration and to offer customized treatments for each patient based on their lifestyles and visual goals have more choices than ever before.