The results after the Surgery
After the Surgery the multifocal lens that will now be sitting behind your pupil will be using typically 60-80% (depending on lens model) of the amount of light for distance vision and the rest, 20-40%, for near (reading) and intermediate (computer) vision. Clearly, the stronger the split of light, the better the near vision and the higher risk of quality of vision symptoms such as glare, haloes and blurry or foggy vision being perceived. A neural process called neuro-adaptation is required to be completed to overcome these symptoms.
This means that the vision may be perceived by you as being a little bit weaker, especially if you are in an environment where the light is not bright enough, for example at night time in winter. Therefore, please do not expect to automatically and immediately have as good distance or near vision as you currently do with your respective spectacles. In other words, when you assess the result of the surgery a day a week, or a month later it would be normal for you to say: ‘yes, I can see well for distance and well for near, however, my vision is a bit blurry.’ The answer to this is because you’re using only 60% of the light on the treated eye for the distance vision and you are comparing this to a scenario that uses closer to 100%.
If you have no need for distance vision spectacles currently and your main intention is to improve uncorrected near and intermediate vision you must accept that your distance or far vision may not be as good after the procedure as it was before.
Side effects and complications
The above is also the reason why the most common side effects occur; glare and halos (or ghosting). Glare at night and ghosting for example happen because when you look in the distance at the headlights of the oncoming traffic or say the subtitles on a movie, the light that passes through the reading part of the lens creates an out-of-focus image (ghost image) that scatters light inside the eye. This is something that the brain will adapt to within months in the vast majority of patients without major issues, but for approximately 1% of patients, the adaption process can take up to one year which may mean that they report that are unable to drive as safely in low light. Assuming clinical suitability, for those that do not adapt, a lens exchange procedure where the multifocal IOL is explanted and replaced with a different form, for example a monofocal IOL, is an option. Other less common side effects include edge effects, narrowing of the visual field, the illusion of seeing through a fish bowl, floaters and dry eyes.
Overall, when asked a year after the surgery approximately 95% of patients are happy with the outcome of their surgery and would recommend it to their friends and family.
Whilst the vast majority of patients do not develop a complication, around 1% of patients will. The vast majority of complications following treatment are minor and can be resolved by further clinical care. These are:
- Refractive Surprise: 10% of the patients (usually their 1st eye) would require an additional procedure such as a laser eye surgery treatment to correct a residual prescription.
- Posterior Capsular Opacification (PCO): Around 30% of patients will require a YAG capsulotomy procedure to overcome PCO. This is an opacification of the bag that surrounds the lens and reduces vision. Patients may describe their vision as being hazy or cloudy when PCO develops. It is easily treatable with YAG-Laser, a 20 seconds non-invasive cleaning done as an outpatient appointment.
- Iritis: 2 to 5 in 100. Mild inflammation after cessation of drops. Treatable with the use of eye drops such as steroid drops, in the vast majority of cases.
- Cystoid Macular Oedema (CMO): 1 in 300. It is a bruising or swelling of the back of the eye starting typically around 2 months after surgery. This condition induces blurred vision for a couple of months but settles spontaneously.
- Posterior Capsule (PC) Tear with/out Vitreous loss: 1 in 1000. A tear in the bag that contains the natural lens and now will have the artificial lens. This may affect the position or choice of lens implantation (this is more likely in older patients with hard cataracts).
- IOL Exchange: 1 in 100. This non-routine surgery involves typically the exchange of a multifocal lens to a monofocal one due to intolerability of SE’s. Surgery takes place 9 -18 months later and results in loss of near vision. Patients who have this done then require near vision spectacles.
- Retinal Detachment: 1 in 3000. A separation of the retina from the wall of the eye – like a wall paper coming off the wall. It is more common in shortsighted patients and those under 50 years old regardless or otherwise of a surgical event taking place.
- Infection: 1 in 5,000. This is the most serious complication and may lead to permanent vision loss depending on the type of microbe involved. Those very rare infections most commonly happen in the first few days or weeks after surgery.