FOCUS POINTS AFTER CATARACT SURGERY
The primary aim of cataract surgery is to remove the opacity within the lens that prevents transmission of light. We do, however, use this opportunity to give the eye a new focus point, to a certain degree of accuracy (90% accuracy).
There are two main focus points as target options: distance (±4m and beyond) and near (reading range, ±40cm). Computer work is generally seen as an intermediate distance at ±60cm, but the near and distance options usually include enough depth of focus to enable reading at this distance. Lenses used at the time of cataract surgery are fixed (cannot change focus point) and therefore only a single focus point per eye is possible.
Please note that with all tactics (except multifocal IOLs), some form of spectacle is usually still necessary as we cannot guarantee a perfect result with this surgery (90% accuracy). If we want to achieve 100% accuracy, we need to include a second optimization procedure. Please see comments on multifocal IOLs and achieving true spectacle independence. Spectacle review is routinely performed at about 5weeks after surgery.
Routine focus point tactics include the following:
□ Plano OU – Standard surgery includes focus of both eyes at distance. This is by far the safest and easiest option, as no adaptation is needed, and the visual quality is as good as it can get. Patients need reading aid, and are often functional without distance spectacles, although optimization spectacles are still advised.
□ Monovision – Dominant eye for distance, non-dominant eye for near. About 90% of patients tolerate this, usually after an adaptation period. Take note that the two eyes are working together to cover both focus points, but they are not working together at the same focus point. This means that there is a loss in quality of vision at both, albeit small. The drop in quality is usually noted for tasks where we use both eyes, e.g. night time driving. For these tasks I strongly advise spectacles to bring the eyes together for these specific tasks. Spectacle independence is achieved for about 95% of tasks. This is not an option for golfers or tennis players, or other sports where tracking fast moving objects are needed. It is also unlikely to be comfortable for rigid or type A personality patients.
□ Micro-monovision – One eye is for distance, the other for intermediate to distance vision. This achieves distance in both eyes, but with a slight offset in the non-dominant eye to give some reading function at about 60cm. Note that readers spectacles are usually still needed for routine near visual tasks, such as reading books or the newspaper. Distance optimization spectacles are necessary less often than for true monovision as above.
□ Myopic OU – Both eyes are targeted at near for full functional reading. Driving or any other distance visual task is then not possible without spectacles. This option is usually reserved for patients that have been nearsighted their entire life and are used to reading without spectacles. This is usually poorly tolerated by patients that have had good distance vision most of their lives.
□ Multifocal IOLs – These lenses achieve distance, intermediate and near focus points within the same eye. Routinely performed in both eyes to achieve comfortably vision. There is quality of vision trade-offs to achieve this however, usually marked at night or any other situation where light levels are low. Patients often see halos around lights, or lights appear to have excessive amounts of scatter. Normal car taillights are often described as having a “Christmas tree” appearance. It is not all bad as this option is routinely performed in some surgical centers, although coming at a greater cost of surgery to patient. Often, patients need further optimization with a second surgical procedure to achieve that 100% accuracy. All that said, this is the only option that offers true spectacle independence. Patients that drive at night often, are strongly advised against this option. Patients with high quality of vision demand, such as golfers or micro-surgeons, this is simply not an option at all in our unit.
If you have any questions about the option chosen for your surgery, please do not hesitate to ask us before we proceed. In more than 90% of cases, I perform standard Plano OU surgery. This is the safest and easiest target to hit with the best quality of vision possible. This is also the most cost-effective option.