During cataract surgery or refractive lens exchange (RLE), an intraocular lens is implanted to replace the natural lens. Without this, the vision would be very blurred. In NHS cataract surgery centres, the only lens option is a monofocal (single focal point) intraocular lens, although some NHS centres do may also provide toric lens for select patients with high astigmatism. Privately, there is no limitation to the intraocular lens available, and there are hundreds of different lens models available from different manufacturers. Many of these have advanced optical designs and so are known as “premium lens.”
In brief, the main intraocular lens types available are monofocal (so similar to the standard NHS lens), multifocal (typically trifocal so three focal points), and extended depth of focus (EDoF) intraocular lens. Toric lens are those that additionally correct higher astigmatism.
Monofocal Lens
Monofocal lens provide excellent vision with one focal point. In practice, this means the eye is usually focused for distance, and glasses are needed for intermediate and near tasks. Intermediate tasks are typically those around ⅔ to a meter away- meaning computer work, cooking preparation, and other tasks. Micro-monovision is when one eye is set for distance, and the other has the focal point pulled back to improve intermediate vision without spectacles, but at the expense of distance-vision clarity in that eye.
Multifocal Lens
Multifocal lens provide multiple focal points, which are typically blended but are usually bifocal or trifocal in design. This means there are three main focal points– distance, intermediate, and near. With this lens design, the aim is to maximise spectacle independence, and it works well for patients who are keen to be spectacle independent for most tasks and willing to accept some compromise. Typically, these lens types cause mild glare or halos around light sources in low vision or at night, but that is the compromise for not needing reading glasses.
Almost all patients with multifocal lens have good distance vision for daily tasks, and can perform most intermediate and near tasks without glasses. Glasses may still be needed for intensive near tasks such as reading a novel or small print, or in poor light situations. For a multifocal lens to work well, both eyes need the same lens type. Overall, this lens type works well in patients who are keen for as much spectacle independence as possible, but are willing to accept some compromise in image optical quality to have this.
Extended Depth of Focus (EDoF) Lens
A newer design of intraocular lens is “extended depth of focus” ( EDoF). In summary, these lenses use advanced optical properties -with zones of differing surface curvature or have a continuous change in power from periphery to centre, which results in the light being focused in an extended longitudinal plane, instead of discrete points. Multifocal lens are not the same as extended depth of focus lens, although some manufacturers have confusingly re-termed some multifocal lens as EDoF lens to try to move away from the stigma of high glare/ halos associated with historic multifocal lens designs.
Examples of EDoF lens include the Alcon Vivity lens. These lenses are designed to give high-quality distance and improved intermediate vision to make everyday tasks easier, with reading glasses typically needed for smaller print or fine near work activities. Unlike multifocal lens, study data shows these lens cause minimal glare or halos, with any being comparable to that with a monofocal lens. EDoF lens are therefore an excellent choice for patients not willing to compromise on optical quality who want good distance and intermediate vision, and are happy to accept they will need reading glasses for most near tasks other than larger print.
Which is better, Monofocal, Multifocal, or EDoF for Cataract Surgery?
The right lens depends on your daily activities, vision expectations, and tolerance for potential compromises:
Monofocal: Best for clear far distance vision, with glasses for near/intermediate tasks.
Multifocal: Best for patients seeking spectacle independence, accepting some glare or halos.
EDoF: Best for excellent distance and intermediate vision with minimal side effects, but will still need reading glasses for small print.
Your cataract surgeon will help you weigh the pros and cons of each lens type and choose the option that best matches your lifestyle and vision needs.
