Extended Depth of Focus lenses: the latest in intraocular lens technology
A cataract occurs when the eye’s natural lens becomes cloudy, resulting in reduction in the quality of vision. In cataract surgery, the cataract is removed and replaced with a clear artificial lens, restoring sight.
Cataract surgery is the most commonly performed and arguably the most successful operation in the world, however, key to the success of cataract surgery is the quality of the intraocular lens inserted.
Over the last 20 years there have been significant advances in the technology of intraocular lenses. Better lenses have led to improvements in the quality of vision, and precision of visual correction – consequently patients are seeing better and requiring glasses less following cataract surgery. The latest advance – and it has been a major advance – is the technology of Extended Depth of Focus (EDOF) lenses.
To understand the role and advantage of EDOF intraocular lenses, first let’s review some of the previous advances over the past 20 years.
Accurate intraocular lens calculation
Like spectacles, intraocular lenses come in many powers. Every eye is unique, and finding the right power intraocular lens for an eye is critical for great outcomes following cataract surgery. This requires measurement before surgery with specialised equipment and carefully calibrated formulae that are continually optimised.
Many advances have occurred in measurement for calculation of correct intraocular lens power. These have resulted in more precise visual correction and less need for glasses following cataract surgery.
Toric intraocular lenses
A toric lens has different powers of curvature at different meridians – it is shaped like a rugby ball (more curved in one direction than another), rather than a soccer ball (same curvature in every direction). By focusing light more strongly in one direction compared to another, toric lenses can successfully correct for astigmatism; astigmatism is one of the most common reasons why people require glasses.
To work effectively toric lenses must be rotated accurately in the right direction to match and neutralise the eye’s natural astigmatism. By substantially reducing astigmatism, toric lenses allow an even greater degree of precision for visual correction in cataract surgery, meaning people see even better and require glasses even less frequently following the surgery.
Multifocal intraocular lenses
While the above technologies provide great distance vision, they do not reduce the need for glasses for near work and reading. Most lenses are monofocal, which means they have only one focus, which can be set for distance (in which case spectacles are needed for near work) or for near work (in which case spectacles are needed for distance work). In comparison, a multifocal intraocular lens provides a wider focal range allowing distance, intermediate and near vision without spectacles.
Multifocal intraocular lenses are not new; for decades people have had the option to have them inserted at the time of cataract surgery, and for the most part these have resulted in distance and near vision without spectacles. This is achieved by concentric rings within the lens – the lens consists of alternating rings of different refractive power, alternatively for distance, intermediate and near.
Multifocal lenses, however, are not perfect and the concentric rings can result in problems with the quality of vision – namely glare, haloes and sparkles around light, as well as a reduction in the quality of contrast sensitivity. This is why they are not suitable for everyone, and some people who have them inserted find these problems intolerable, which often results in them having the multifocal intraocular lenses later removed.
Extended Depth of Focus lenses are new, and represent a significant advance in intraocular lens technology.
EDOF lenses are similar to multifocal lenses, in that they allow vision over a wide range of viewing activities – distance viewing (such as driving, playing golf, watching TV), intermediate viewing (reading items on a supermarket shelf, using computers) and near viewing (reading, sewing). Critically, EDOF lenses achieve this in a different way to multifocal lenses so that most of the problems associated with multifocal lenses are avoided. This is because, while multifocal lenses create multiple focal points, which can be hard for the brain to adjust to, an EDOF lens creates a single elongated focal point to achieve a wide range of focal distances. For EDOF lenses the problems of glare, haloes and sparkles are not so prominent. It is much more uncommon to need to remove an EDOF intraocular lens than a traditional multifocal lens.
However, there are some drawbacks to EDOF lenses. Not everyone is suited to an EDOF lens, a person’s suitability to EDOF lenses is based on the health status of the eye, and the critical pre-operative measurements. Eyes with unusual surface curvature, or eyes with significant other problems such as age-related macular degeneration or glaucoma might not be suitable. Also, while EDOF lenses are great for distance and intermediate range, they may not be so effective for very near work. This is why people who have EDOF lenses still may require reading glasses for fine print or close work.
EDOF is a new technology and holds promise for many people who desire to be spectacle independent following surgery, without many of the problems associated with some other lenses that allow a wide range of viewing distances.
As an Ophthalmologist in Melbourne, Dr Simon Skalicy is continually keeping up to date with the latest technologies used in cataract surgery to provide patients with the best outcome. To discuss booking your own cataract surgery in Melbourne, contact us today.