Most of us must have seen our grandparents or great grandparents using thick unsightly glasses after having undergone cataract surgery. These glasses looked like big magnifying glasses. People needed to use these glasses to compensate for the loss of refractive power of the eye, which occurred because of removal of the natural lens during cataract surgery. It was an English ophthalmologist called Harold Ridley, who first suggested that a lens could be implanted inside the eye instead of using thick glasses post operatively.
It was as early as in 1949 that Ridley implanted the first intraocular lens (IOL), made of glass, in the eye. However, it took another four decades for the lens design and materials to be refined and perfected for intraocular use, and the IOLs became popular only in late eighties. Nevertheless, this idea did change the course of ophthalmology and the life of cataract patients forever. Now, implanting an IOL is commonplace and in fact an integral part of cataract surgery. As a result, patients no longer have to wear those thick ugly glasses after the surgery, and can see well with ordinary very low power glasses or without any glasses at all.
Currently there are many types of IOLs available. When you approach a surgeon for your cataract surgery, you will have to make an informed decision with the help of your surgeon, as to which type of IOL you will prefer. Although, sometimes if there is a specific need for a particular design or material for your eye, your surgeon may decide as to which IOL is to be used, but mostly the surgeon will give you the alternatives and will like to know about your preference about the type of IOL. Factors that you will have to consider in making a right choice of IOL for you:
- What is the nature of your profession? Do you have an office job or an outdoor job? Do you have to do very fine work like graphics, painting or carving, etc.?
- What is your lifestyle and hobby? Are you an ‘indoor’ person, or do you have interest in outdoor activities, sports, swimming, mountaineering etc.?
- Do you need excellent unaided vision as per the need of your profession, like pilots, drivers, etc.?
- How important is night vision or vision in dim light for you for your job or activities?
- What is the nature of your refractive error: near-sightedness, or farsightedness? Do you have astigmatism or a cylindrical glass power?
- Would you mind using glasses routinely after the surgery or would you rather not?
- If you are paying for the cost of your surgery from your pocket, what is your budget? The cost of certain IOLs can be exorbitantly high.
- It is also important for you to know about various types of IOLs and their features.
Let us see what different types of IOLs are available. IOLs come in different materials, designs and optical properties.
- Material: Various materials that IOLs are made of include:
- Poly methyl meth acrylate (PMMA)
- Acrylic hydrophilic
- Acrylic hydrophobic
PMMA lenses are rigid lenses and can’t be folded, and therefore require a large incision (about five mm) to be inserted in the eye. These IOLs are very low cost. IOLs made of the other three materials are soft and are foldable, and hence can be inserted through a very small incision (up to one mm) by folding them into a small size. Once inside the eye, they open into their full size. Acrylic lenses are generally preferred over silicone as the latter can be problematic in certain situations. Out of the acrylic ones, hydrophobic material is thought to be friendlier to the eye as compared to the hydrophilic one; however, that issue is debatable. In any case, the decision regarding which material IOL to be used, will be usually taken by the surgeon.
There are a large variety of lens designs available, and the surgeon will usually like to know your preference as well as affordability for the IOL to be used.
- Monofocal IOLs: These are the simplest type of IOLs available. These IOLs give you good distance vision, but you have to use reading glasses for near work or reading. These IOLs are relatively low cost. If you don’t want to spend too much and don’t mind wearing glasses after the surgery, you can opt for this IOL.
- Multifocal IOLs: These IOLs not only give you good vision for distance, but give you good near vision as well; so one can manage most of the needs for distance and near vision with this lens without using glasses. However, one may still require glasses for reading very fine print like a telephone directory. Also, vision at middle distance may not be very good, e.g. looking at the computer monitor. Another drawback is that some patients complain of glare while driving at night, and so it is not suitable for people who routinely drive at night. Cost of these IOLs is high. So, if you don’t like to wear glasses, don’t drive much at night, and if you can afford its price, you can go for multifocal IOLs.
- Accommodative IOLs: These lenses are designed in such a manner that they, like the natural crystalline lens of the eye, can change and hence give good vision without glasses for all distances. These lenses, although in use currently, are extremely costly and their design has not been perfected yet. Sometimes, they fail to give the desired result and also their capacity for providing near vision can decrease with time. If you have a fad for the latest things and don’t mind the cost, you may go for it, keeping the possible shortcomings in mind.
- Toric IOLs: These IOLs, unlike other IOLS, can also correct astigmatism or cylindrical power. So people who have cylindrical number in their glasses and want to get rid of their glasses can benefit with these IOLs. Sometimes these IOLs may need to be readjusted after the initial surgery and are quite costly. Also, you can get a multifocal IOL combined with a toric design, but again the cost is very high.
- Aspheric IOLs: The lenses have a design, such as used in cameras and telescopes, which increases the quality of vision by removing or reducing the optical aberrations. These IOLs give a better quality or contrast sensitivity, particularly at night time. These IOLs cost more than the routine IOLs, but only marginally, so people who require better quality of vision like artists, drivers, pilots, graphic designers, etc, can opt for this IOL.
- Blue light filtering IOLs: These lenses have a yellowish pigment impregnated, which cuts off blue light. Blue light is harmful for the sensitive part of the retina called the macula, and normally is cut off by the natural lens. However, the normal IOL doesn’t block it and hence the macula is at risk to be damaged by the blue light. So, people who have macular degeneration can opt for this IOL. Cost is similar to normal or aspheric IOLs.