The most frequently implanted lens is a monofocal IOL (standard IOL). This lens offers excellent image quality (especially in aspheric form) and is primarily used to achieve good distance vision. Monofocal lenses of different powers can be implanted so that one eye is corrected for distance and the other for close vision, helping the patient to minimise reliance on spectacles for reading and other close work. This is known as monovision. Some patients acclimatise to monovision more easily than others; in some cases reading glasses may still be preferred for fine print, and a distance prescription may help with some activities, particularly in poor light conditions.
Multifocal IOLs have grown in popularity in recent years allowing for an element of close work vision not present with standard monofocal lenses. The more modern designs have now overcome some of the limitations of earlier examples. These lenses can be well tolerated and can give reasonably good distance and close vision, with a greater depth of focus than monofocal IOLs. However, this is sometimes at the expense of image quality, and glare and haloes may be troublesome. We would not recommend multifocal IOLs for those who drive frequently at night, for example, or those with very exacting visual requirements. These lenses can also be used in the treatment of presbyopia (the loss of near vision as we move into our mid 40s).
Toric lens implants are for patients with moderate amounts of corneal astigmatism (more than 1 or 1.5 dioptres). Reducing your astigmatism will reduce your dependence upon glasses as compared to a non-toric IOL. A standard IOL can be set to make you either far sighted or near sighted but if you have astigmatism your vision without glasses will still be blurred to some degree because this astigmatism has not been corrected by the standard IOL. You could wear glasses in order to correct the astigmatism or undergo laser eye surgery at a later date (Bioptics). However if it is desirable to you to have better vision when not wearing your glasses, you may want to consider a toric lens implant.
These lens implants are the same as the above Toric IOLs but have a +1.5 dioptre reading addition built in to aid near vision.
With cataract and refractive lens exchange surgery the eye’s natural lens is removed and replaced with an artificial implant. Some ophthalmic surgeons perform an alternative procedure – phakic implant surgery – where the natural lens remains in place while the phakic IOL is positioned immediately in front of it.
The combined focusing power of the two lenses can be effective at treating severe short and long-sight, and the artificial lens can also reduce or eliminate astigmatism. David Gartry does not perform phakic implant surgery, as it is a relatively new procedure and he is unconvinced as to its long-term effectiveness and safety. These lenses tend to be used more for younger patients who can still accommodate (focus for close work) who are contact lens intolerant and have high prescriptions. Beyond mid 40s a better option is refractive lens exchange using the new femtosecond laser technology. Phakic implants have been known to cause cataract and glaucoma and, since the technique is intraocular (placing a lens inside the eye), rarely serious problems such as infection or retinal detachment can follow. If at all possible David Gartry encourages these younger patients, who are well beyond the normal laser range, to persevere with contact lenses – perhaps seeking the advice of an experienced contact lens specialist.