Refractive cataract surgery with premium IOL implants provides a unique opportunity for patients to achieve life-changing vision. However, not all lens platforms, including toric lens platforms, are created equal.
This article was reviewed by David A. Goldman, MD.
Beyond relying on training, surgical skills, and experience, surgeons must have ultimate confidence in the technology they use in practice and the vision-correction strategy they recommend to patients.
To incorporate IOL solutions that can provide outstanding, dependable, and consistent refractive outcomes requires understanding the attributes of each platform. Equally important is the ability to pivot when the clinical and scientific data warrant a change.
Pick your platform theory
The eye’s spherical aberration (SA) is a combination of the positive SA of the cornea and the negative SA of the crystalline lens. In younger eyes, the positive SA of the cornea is coupled and balanced by the negative SA of the lens. With normal aging, this balanced coupling is disrupted causing decreased optical performance.1
Over time, theories have shifted along with surgeons’ preferences with regard to lens sphericity and its relationship to visual outcomes. Traditional spherical IOLs were designed with positive SA, which increases the positive SA in the eye postcataract surgery.
In the early 2000s, a new generation of lens was developed with asphericity, which more closely mirrors the natural crystalline lens.
Today’s aspheric IOL models offer different degrees of SA from negative (Tecnis IOL, Johnson & Johnson Vision), low-negative (AcrySof IOL, Alcon) to zero (enVista IOL, Bausch + Lomb).
Companies have designed aspheric IOLs with an anterior prolate surface (Johnson & Johnson Vision), a posterior prolate surface (Alcon), or with both anterior and posterior prolate surfaces (Bausch + Lomb), and these models compensate for corneal SA to varying degrees.
The Tecnis platform (Johnson & Johnson Vision) and AcrySof Restor (Alcon) aim to correct positive SA from the cornea. The enVista IOL (Bausch + Lomb) has zero SA and thus preserves the cornea’s natural sphericity profile. I favor this zero-sphericity approach because it provides my patients with an increased tolerance to defocus.
When the cornea’s SA is completely neutralized, the patient will have good contrast sensitivity, but at the same time, will notice a trade off in terms of the limited range of clear uncorrected vision.
For many patients, enVista functions with an excellent range—a big “sweet spot” to hit the intended refractive target. Patients with previous hyperopic LASIK will have eyes already presenting with negative spherical aberration, implanting a zero sphericity IOL is a great choice, in my opinion.
There is no concern with angle kappa, as the implant’s asphericity makes it more forgiving in its use. In patients with high angle kappa or lens decentration, a negative spherical aberration lens may produce suboptimal visual outcomes.
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