Emulating the young human eye, which sees clearly in the distance and at close range, remains the ultimate goal following cataract surgery. Dr Holcombe is a highly skilled eye surgeon and uses the advanced keratometry of the Lenstar optical biometer and premium intraocular lens implants to bring you as close as we can to that goal.
Clouding of the lens
Inside our eye is a structure called the lens. This helps focus light onto the back of our eye (retina) to facilitate vision. A cataract refers to the clouding of the lens itself. Some people think that there is a film that grows over the eye, but it is actually a clouding of the whole lens structure. Most cataracts are caused by the normal ageing process. This means that if you live long enough, you will develop cataracts. In some people cataracts develop at a younger age. Factors that may cause the early development of cataracts include eye trauma, ultraviolet light exposure, smoking, some medications, and diseases such as diabetes.
Specialist slit lamp examination reveals the clouding of the lens which is the key feature of cataracts
From the day you are born to the day you take your last breath, the lens inside the eye becomes increasingly yellow tinted. This constitutes a cataract, but at the early stages it may not affect your vision at all. As the cataracts progress however, you may notice any or all of the following:
- you have difficulty with fine detail work, such as threading a needle or reading small print
- you need to update your glasses or contact lenses more often and they just don’t seem to give you the clarity of vision you are used to
- you are bothered by symptoms of glare; this is noticed particularly when driving at night and oncoming car headlights are dazzling, or other lights are “fuzzy” or have a “halo” or “glow” around them
Currently the only treatment for cataract is surgery. Many people ask, when is the right time to do surgery? The answer with any surgical procedure is a balance of the risks and benefits, but surgery should be considered once your cataracts are interfering with your life, and are preventing you from doing the things that give you enjoyment. Occasionally some people are not bothered by their cataracts, but their vision has worsened to the point that they no longer meet the legal standard required for driving vision. In this situation if the patient wishes to continue to drive, then surgery would be required.
Cataract surgery is the most common eye operation, but it is not a trivial procedure. It is a delicate operation in which the cataract needs to be removed, whilst preserving certain structures within the eye in order to be able to place a new lens implant into the eye at the end of the operation. As the natural lens of the eye is an optical structure, an optical structure needs to be replaced in order to refocus the eye at the end of the procedure. More will be discussed on this later.
Cataract surgery planning
Cataract surgery is usually a day procedure performed under a local anaesthetic with twilight sedation. Dr Holcombe uses topical anaesthetic drops and gentle sedation to facilitate your surgery thus avoiding the risks associated with eye blocks. Once the local anaesthetic and twilight anaesthetic is administered, the operation is performed. A small 2.2 mm incision is placed on the eye and the cataract is broken up inside the eye into tiny pieces and “vacuumed” out. The whole procedure is generally painless. Once the cataract is removed an intraocular lens implant is inserted into the eye.
Prior to your operation you will have your eye measured on the Lenstar LS900. This advanced machine is the only one of its type in Toowoomba.
Lenstar optical biometry with advanced keratometry is used to precisely plan individualised cataract surgery
After your surgery you will spend a short time in recovery then you will be ready to leave. You will need someone to drive you home. There is minimal discomfort from cataract surgery performed with local anaesthetic and twilight sedation. Some patients say they have no discomfort, some say that the eye feels a little scratchy. Over the counter medication such as paracetamol, if anything, is usually all that is required to control any discomfort. An information sheet and eyedrops will be provided after surgery and a post-operative appointment will be made for you.
Intraocular lens selection
The original goal of cataract surgery was to clear the line of sight, and glasses were used to fine tune the focussing to provide the patient with sharp vision. With the accuracy of the measurements provided by the Lenstar LS 900, new calculation methods for manipulating this data, and the accuracy of implantable lens manufacture, we now live in an era where it is possible to ‘reset’ the focus of the eye at the time of cataract surgery. Whilst the results anywhere in the world are still not 100% accurate, with advances in technology they are better than they ever have been before. Hopefully by the time I need my cataracts done the calculation accuracy will reach 100%!
How I reset your eye’s focus at the time of cataract surgery really depends on what you like to do with your vision, the activities you participate in, and the lifestyle that you lead. The ‘holy grail’ of intraocular lens implantation is to be glasses free for everything – that is, see in the distance and read small print up close without the aid of glasses, much like many young people do.
Unfortunately the technology does not exist yet whereby this outcome can be provided reliably and without side effects to patients. Once again, something that I hope will be sorted by the time I need my cataracts done! Consequently, compromises and decisions must be made about the type of vision, and hence lens implants you would like.
Essentially there are four main choices:
- Both eyes distance vision
- One eye distance, one eye close (monovision or blended vision)
- Extended depth of focus lenses
- Multifocal intraocular lenses
Both eyes distance vision
This is the traditional and most common focus target when implanting intraocular lenses. It provides excellent distance vision but patients usually require reading glasses and often computer glasses. It provides the best distance and night vision possible and preserves stereovision as both eyes are still working together. If wearing glasses for near work does not bother you, then this is the simplest and least complicated option.
One eye distance, one eye close (monovision or blended vision)
We all grow up thinking that the focus of both eyes is the same, and in most people it is, but there are some people who naturally have one eye for distance and one eye for near. Once they have passed their mid forties, when the rest of us need reading glasses, they happily carry on reading and seeing in the distance without glasses! At the time of cataract surgery we can set the eyes similarly. The focus of the dominant eye is set for distance and the focus of the non-dominant eye is set for closer. Most people’s brains are able to adapt to this new focus blend and pay attention to the eye that is providing it with the sharpest image for what it wants to see. The closeness of the focus in the near eye will determine how well the eyes ‘focus together’ and whether occasional reading glasses will be required for very small print. There can be some reduction in depth perception and peripheral vision so for high visually demanding tasks that require the eyes to focus together (binocular vision) such as driving at night in the rain, corrective glasses may be used.
Determining if your brain will ‘accept’ monovision and if you will like having that type of blended focus between the eyes can easily be tested before a decision is made by wearing a contact lens in one or both eyes for a trial period. This will give you a sense of what monovision will be like, however the brain continues to adapt for several months to the new blended focus and patients generally like it more with time. In some cases, the brain will never adapt or accept a different focus between the eyes, which is why a contact lens trial is important.
Extended depth of focus lenses
Extended depth of focus (EDOF) lenses are a new technology that has recently emerged. They aim to provide sharp vision not just at one focal distance, but rather over an ‘extended range’. This ‘range’ usually begins in the distance and extends towards the patient, providing the patient with good distance vision and enhanced intermediate vision for activities such as television viewing or computer work. Patients often still need reading glasses to read small print up close. One advantage that extended depth of focus lenses have compared to monovision or blended vision is that there is greater preservation of stereopsis (both eyes working together to give 3D vision). Furthermore, they work on a different optical principal to multifocal intraocular lenses (described in next section), and so they have a lesser amount of the disruptive visual phenomenon such as glare and halos. Some published studies have shown the levels of these to be no greater than monofocal intraocular lenses. If you do a lot of night driving and are very particular about glare and haloes then you may be better off with monofocal lenses, but if not, then these lenses can provide a greater degree of spectacle independence. These lenses are also available in ‘toric’ models that aim to correct as much of your existing astigmatism as possible.
Multifocal intraocular lenses
In an effort to attain the “Holy Grail” of vision – clear distance vision and clear near vision without glasses, lens manufacturers have developed lenses which do not just have one set focus, but three within the same lens. This is an attempt to focus light from the distance, intermediate, and near so as to provide a sharp image at each distance. Unfortunately due to limitations in technology, the optical principle used to perform this task in multifocal intraocular lenses is not the same that a natural young eye uses, and so there are a few visual compromises that must be accepted if you are considering implantation of this type of intraocular lens. Whilst the latest generation of multifocal lenses are better than they have ever been, because of their design, patients can notice halos around lights at night, and may notice a sparkly appearance around bright lights during the day. Most people cope well with these phenomenon, but occasionally they can be very off-putting. On the up side, if multifocal intraocular lenses are implanted in both eyes, they allow for better peripheral vision and binocular vision than monovision or blended vision. Also they provide the patient with the opportunity, for the majority of activities including reading, to be glasses free. Unfortunately there is no way to determine before lens implantation how significant the visual symptoms or loss of sharpness from multifocal intraocular lenses will be, remembering that these phenomenon are not correctable with glasses. Some people never fully adapt to their vision with multifocal intraocular lenses and in rare cases this will be significant enough to warrant removal of the multifocal lens and replace it with a non-multifocal lens. Others will enjoy a wider range of glasses free vision whilst accepting the negative visual phenomenon.
If you are considering cataract surgery, Dr Holcombe can discuss all your available options to find a strategy that will most closely match the visual requirements of your lifestyle.
Contact Toowoomba Ophthalmic Consultants today