Cataract Surgery Logo
Call Us (08) 8359 2422

Types of artificial lenses

When your cataract is removed it is replaced with a small clear plastic lens, without which you would need extremely strong glasses to focus. So all patients receive this plastic lens implant known as an intraocular lens or IOL. 

With cataract lens replacement, several types of IOL implants are available to help people enjoy improved vision.

Intraocular lenses (IOLs) are small (approx 11-13mm wide) lenses placed within the eye to assist in focussing light on the retina. All IOLs manufactured today have UV filters. None are transitional ie go dark in bright light like some spectacle lenses.

They consist of a focusing element - the optic - and elements that support the lens in the correct place within the eye - the haptics. IOLs are transparent but all of or just the IOL haptic may be coloured for a variety of reasons.

There are many different types of artificial lenses and it’s important to talk to your doctor about which best meets your needs.

IOLs can be described by the material the IOL is made of. One group is called ICLs or intraocular collamer lenses. Collamer is a particular material used for making a particular type of IOL inserted like an intraocular permanent contact lens to correct blurred vision. However most IOLs are made of silicon or acrylic. All IOL materials are biocompatible, ie they do not incite immune rejection of the IOL by the eye. All are inert, that is they do not degrade with time and last as best is known for your entire life in your eye.

IOLs can be described by their use. Phakic IOLs are placed into the eye in addition to the eye's natural crystalline lens, which is not removed. Pseudophakic IOLs are placed after removal of the eye's natural crystalline lens for vision correction or cataract removal reasons.

IOLs can also be described by where in the eye they are put.

Anterior chamber IOLs (AC IOLs) are placed between the cornea, the clear front window of the eye, and the coloured part of the eye, the iris. Posterior chamber IOLs (PC IOLs), or sulcus based IOLs, are placed behind the iris, but in front of the crystalline lens, unless the crystalline lens has been removed. Then the PC IOL is usually placed within the capsular bag component of the crystalline lens that is usually left behind to secure the IOL after modern cataract surgery.

Finally IOLs can be described by the way they bend light. Monofocal IOLs focus light from one image location only.Objects in the real world can be considered to be located in front of a person either far away, at an intermediate distance (like a computer monitor) or near (like a book). A monofocal lens will allow vision in an eye without am accomodating crystalline lens (one that changes shape to focus in from distance to near) at just one of these three locations. Patients these IOLs will usually require spectacles or contacts for other distances.

A monofocal IOL corrects just myopia or hyperopia. A toric IOL also corrects astigmatism, either with or without myopia or hyperopia allowing clear vision only at one of the above three distances. Patients with these IOLs will usually require spectacles or contacts for other distances.

Monofocal or toric IOLs can be used in a process called "Monovision" where an IOL is implanted in each eye, but in one eye (usually the "dominant" eye) the IOL is in focus for distance, and the fellow eye in focus for intermediate or near. This is a modern version of the old fashioned monocle (but cannot be placed and removed at whim!). Many contact lens or vision correction patients use this technique very successfully to reduce how much they use glasses.

Multifocal IOLs split light entering the eye into different pathways so that light from distant and also near objects, and to a lesser degree intermediate distance objects, can be in focus on the retina at the same time. The degree to which the near of distance focus is predominant usually depends on the patient's pupil size, which gets smaller as we try to read. A process called "neuroadaption" is then required whereby the patient's brain, where the sensation of vision is created (we actually see with our brain not our eyes) learns to see the predominant of the distant and near images on the patient's retinas. This can take some weeks or months after multifocal IOL insertion. Most multifocals do not provide the quality of vision at a single distance in the real world that a monofocal IOL can provide and are therefore to some degree a compromise, but one that can work extremely well for the right patients who are motivated to use glasses as little as possible day to day. Multifocal IOLs can correct myopia, hyperopia and astigmatism at the same time. Multifocal IOLs are usually, but not always, placed in both eyes for best effect.

Both monofocal monovision and multifocal IOL use after crystalline lens removal are a compromise between distance and near vision, do not provide total independence from glasses, and approximate but are not the same as a normal 21 year olds distance and near vision. Therefore they are perhaps best for patients who display some degree of motivation to reduce spetacle dependence for both distance and near tasks, and who understand they will still need glasses for visual tasks at extremes of distance or near, such as driving at night or reading a telephone book or threading a needle.

Accommodating IOLs change their separation of their front and rear curvatures to allow vision at different distances, therefore most closely matching the focus action of the natural crystalline lens that they usually replace. These are distinct from pseudo-accommodating IOLs where a similar change in curvature of the IOLs front and rear curvatures occurrs. Accomodating IOLs are under development but there are currently none in general clinical use in Australia.

Pseudo accommodating IOLs usually can provide some degree of focus from distance to intermediate, or intermediate to near, but are generally not thought in their current forms to provide clear focus for real world objects over a broad range of distances from the patient.

Phakic ICLs are almost always used to correct blurred vision where, because of the ICL, there is no need to remove the patient's natural crystalline lens. This means the eye's normal anatomy and physiology is minimally altered. It also means the young patient, who can still accommodate (ie can change the crystalline lens's shape and focus to read), will not need reading glasses when the ICL corrects their myopia, hyperopia or astigmatism. This is in comparison to the use of a non-accomodating pseudophakic IOL to correct blurred vision, which requires the compromise of monovision or multifocal IOLs to allow some reduced dependence on reading glasses.