Intraocular Lens Choice
Cataract surgery has advanced to the point that we can now not only remove your cataract, but also correct your long sight, short sight or astigmatism all at the same time, significantly removing your need to wear spectacles.
When you have your cataract removed your natural lens needs to be replaced with an artificial lens. These artificial lenses come in many different powers such that a lens can be chosen to take into account your current need for spectacles and correct that need. There are now many different intraocular lenses available.
To know which is best for you, you need to know your current spectacle prescription, and whether you want to continue to wear glasses after your surgery. While many patients are very keen to minimize their spectacle use, there are also a significant number who very much like their glasses, and do not want to stop wearing them.
Intraocular lens types:
There are currently four broad types of intraocular lens. Monofocal, toric, multifocal and accommodating.
Monofocal Lenses
The monofocal lens is the most popular lens. This type of lens is the lens available on the NHS. The modern monofocal lenses have now developed to have a curved shape, "advanced aspheric optics" to focus all the available light onto the retina. The power of the lens is chosen to match your eye. The lens is usually chosen to give you the best possible distance vision. As the lens has a fixed focus and cannot zoom in and out you will normally also need to continue to use reading glasses. These lenses do not cause halos or ghosting and help maximize contrast sensitivity, (the ability to see in dim light). Patient satisfaction with the lenses is incredibly high, even if they still need reading glasses, as the quality of the vision with the reading glasses is also excellent.
Toric Lenses
A toric lens is shaped so that it can correct your astigmatism. These lenses have all the advantages of the monofocal lenses but with an additional astigmatic correction built into the curvature of the lens. Like the monofocal lens you should then have excellent distance vision without glasses but may still need reading glasses for small print.
The vast majority of patients have been using reading glasses for years and are quite happy to continue to do so. However a significant number of patients are keen to stop using reading glasses. For these patients there are three options, monovision, multifocal lenses and accommodative lenses.
Monovision
Monovision is the term given to the technique of inserting a monofocal lens set for distance in one eye and a monofocal lens set for reading in the other.
Your stronger or dominant eye is usually operated on first aiming to give you good distance and middle distance vision. Your non-dominant eye is subsequently treated with a lens chosen to give better middle and near vision in that eye. There should be no problem using the eyes together, no blur circles or glare, and significant spectacle independence. As a further advantage, patients who think they may like this solution can try it pre-operatively using a contact lens to the non-dominant eye. For the patiens who find this solution comfortable there is no trade off, the overall vision with both eyes open is excellent for all distances.
Multifocal Lenses
Multifocal lenses have the lens curvature adjusted such that some of the light from near, some from middle and some from distance is focused onto the retina at any point of observation. When looking into the distance the distant light rays are in focus with the near rays ignored and vice versa for near. These lenses need to be placed in both eyes and can take some getting used to. They can give the most significant spectacle independence with excellent
near and distant vision but are associated with some patient dissatisfaction due to blur circles, glare and reduced contrast sensitivity. The technology continues to improve and the latest lenses are showing better patient satisfaction than the earlier designs. As a general rule there is still a trade off. In order to do away with your spectacles you have to put up with some side effects.
Accommodating Lenses
Accommodative lenses are based on the theory is that they should move inside your eye and zoom in and out to provide you with the ability to see both near and far, just as your natural lens did when you were younger. In studies, following the lens movement with ultrasound has not always shown enough movement to account for their effect. So how do they work? Patient satisfaction suggests they do improve the ability to see both near and far, with significant spectacle independence and fewer blur circles or glare than multifocal lenses. This has been complicated by the recommendation that the lenses are inserted in slightly different powers in each eye. They may therefore work in exactly the same way as the less expensive monofocal lenses, by simply setting one eye more for distance and the other more for reading. Surgical opinion is divided, with some surgeons very interested in these lenses and others considering them expensive monofocal lenses. They have the disadvantage of being more difficult to remove if they cause a problem.
The desire to find the perfect lens is driving much research amongst eye surgeons. There is not yet any consensus on which lens combination is best. Each surgeon has their own preference.
There is an additional cost to toric, multifocal and accommodative lenses.
The premium lenses are not routinely available on the NHS at present.
Freedom from Spectacles
For some patients the wearing of glasses and the constant on off on off on off of reading glasses becomes unbearable. For this group of patients there is now the option of premium multifocal intraocular lenses.
The treatment options have been heavily advertised in the media and the process has been know as "Prelex", "Refractive lens exchange" and most recently "Clarivu" . The underlying treatment is exactly the same - cataract surgery to remove your ageing lens and its replacement with a premium multifocal intraocular lens.
There is a trade off however that must be fully understood before any patient makes this choice. Essentially all multifocal lenses will cause halo's and glare. This is most evident when driving at night, but can be annoying when under bright striplighting.
The sequence of treatment is also more complex and inevitably more expensive. The steps involve:
1. Pre-assessment to include corneal topography, refraction, biometry, and dilated fundoscopy.
2. Pre-treatment prior to the surgery with artificial tears and antiinflammatory drops.
3. Rapid sequential bilateral cataract extraction and lens insertion.
4. Artificial tears and anti-inflammatory drops post op.
5. A period of adjustment to the halo's and glare. Almost all patients dislike these symptoms for the first 6 weeks but almost all are no longer bothered by them by 6 months.
6. YAG laser capsulotomy treatment is usually required at 3 months.
7. For 5 to 10% of patients additional laser surgery is required to sharpen the vision.
8. A small number of patients cannot get used to the multifocal lens and it then needs to be removed and swapped for a normal lens.
The multifocal lenses are however effective. The simple stats are:
Without multifocal lenses 90% of patients need to wear reading glasses and 10% suffer glare.
With multifocal lenses 10% of patients need to wear reading glasses and 90% suffer glare.
Am I a suitable patient?
Multifocal lenses may suit you if:
1. You are happy to swap the need for reading glasses for some halos and glare.
2. You do not suffer with moderate or severe dry eye.
3. You do not have any early macular degeneration.
If you think you would be interested in multifocal lens implants then you would need to discuss your options with your cataract surgeon. These lenses are not available on the NHS.
The typical all inclusive cost for the pathway is £3400 per eye - about £1000 more per eye than normal cataract surgery