5 Things You Should Know About Cataracts
- Cataracts are more common with age
Cataracts are among the most common of eye conditions, and among the most frequent causes of vision loss worldwide. Fortunately with modern surgical care, they are treatable and the vision loss is reversible.
Cataracts are very rare when we are young and in middle age, but as we get older, cataracts become more prevalent. In the US, 40-50% of people develop cataracts by their seventies, and 50-60% by their eighties. Cataracts have a similar age-based prevalence in other parts of the world.
- Cataracts cause painless loss of vision
A cataract is an opacity that develops within the eye’s natural lens. Located towards the front of the eye, the lens is clear at birth; as we age it can accumulate opacity (cloudiness). This is mainly due to oxidative stress from sunlight throughout life; fortunately our lenses have plenty of antioxidative mechanisms to combat this and keep them clear, but as we age the antioxidants within the lens become fewer and less effective, unable to combat the oxidative damage which develops into opacities. These opacities scatter the light that enters the lens, resulting in blurred or cloudy vision.
Cataracts may also cause glare at dawn or dusk or from oncoming headlights as the opacities within the lens scatter light. These changes may interfere with many daily activities, such as driving, watching TV, working on the computer, reading the newspaper or walking down the street. However, cataracts do not cause pain or discomfort in the eyes.
- Not all cataracts require surgery
Cataracts develop slowly over time, and often when they first appear, they do not greatly impact a person’s vision. Commonly, the first symptom of a cataract is a change in the eye’s refractive state – this means a change in the strength of eyeglasses a person uses to see clearly. This is because before cataracts cause opacity in the lens (scattering of light), they cause a hardening of the lens, with increased refractive index within the lens (greater bending of light) which can be fixed by a stronger pair of eyeglasses.
For some people, this change in the refractive power of the lens is helpful, and often near-vision activities (eg reading, sewing) that were difficult, are now easier. People call this the “second sight” that often happens in their sixties due to early cataract formation.
As cataracts progress, the change in refractive index continues, which means the need for an update in eyeglasses. A common early symptom of cataract is needing to get one’s eyeglasses script updated frequently.
It is only when a cataract is relatively mature that updating the spectacles no longer can improve the vision; this is when cataract surgery is considered.
- Cataracts are successfully treated globally
Globally, cataract surgery is the most commonly performed operation; and arguably the most successful. Why so successful? Because cataract surgery has a very low complication rate, very predictable outcomes and rapid recovery. It is efficient, quick surgery that does not require heavy anesthetic or an overnight stay in hospital. And the impact of cataract surgery is breathtaking. Removing the patch form my patient’s eye on day 1 post surgery is often an emotional experience for us both; I never take for granted the opportunity to help so many people so meaningfully.
Can we do things better still? Of course. At the end of an operation, while I am so happy to have performed great cataract surgery, it pains me to see the large amount of plastic and other waste generated by the surgery. It does not necessarily need to be so. In some centers, in India for example, high volume cataract surgery is being performed at a high standard at only a fraction of the waste that is generated in the developed world. In developed world healthcare settings, such as in Australia and the US, the emphasis is on single-use disposable equipment to maximise sterility and minimise infections. Obviously this is important, but I hope that in the future we can have a mature conversation within healthcare centers about getting the balance right between sterility requirements and carbon footprint.
- New intraocular lens choices are available
When cataract surgery is performed, the cataract is removed, and a replacement artificial intraocular lens inserted in its place. The technology behind these IOLs is incredible, and has progressed significantly in recent years. This means people following cataract surgery will see even better, and rely less on glasses for their various activities.
The latest intraocular lenes achieve the following:
i. Minimising aberrations
The earliest intraocular lenses, while achieving focus on a single point, caused aberrations in vision, resulting in reduced quality of vision overall. This is mainly due to light going through the periphery of the intraocular lens, where these aberrations cause the greatest impact. Functionally this occurs when the pupil is large allowing light access to the peripheral intraocular lens; leading to worse vision at night. Today’s intraocular lenses have all sorts of clever design features to minimise such aberrations resulting in more consistently clear vision day and night.
ii. Better formulae for IOL power calculation
Eyes come in all shapes and sizes, which ultimately affect their refractive power (how strongly they focus light). It is the job of the cataract surgeon and surgical team to choose the right power intraocular lens to best match an individual’s eye. This is achieved through careful pre-operative measurements and application of formulae to convert these measurements into the optimal intraocular lens power. Recent improvements in the accuracy of our pre-operative measurements and the formulae we use to calculate intraocular lens power, has meant better and more predictable visual outcomes for patients.
iii. Excellent control of astigmatism
Astigmatism occurs when the eye refracts (bends) light unequally in one direction versus another; this is often caused by an uneven curve in the cornea. An intraocular lens known as a “toric lens” can be crafted to correct astigmatism. This technique has recently been enhanced further by Computer Assisted Cataract surgery: eye-recognition software to enhance lens positioning for superior outcomes.
iv. Options for correcting presbyopia
Presbyopia is the problem that most of us get from our 40s onwards: we need extra eyeglasses strength to see near things. When we are young, we can easily see far in the distance and read near without trouble – this is because our natural lenses can change shape (and focal power) to accommodate this shift in focal point. By our 40s, our natural lens has lost the ability to make this change and hence we require reading glasses for near.
Designing an intraocular lens that effectively corrects presbyopia has been challenging and an avenue of great effort in research and development over decades.
Traditionally we have used monofocal intraocular lenses most commonly in cataract surgery. Monofocal intraocular lenses enable a person to focus clearly for medium to long distance objects. Glasses are usually necessary for reading or working on things up close.
Multifocal intraocular lenses have been available for decades to correct presbyopia. Multifocal intraocular lenses encompass magnification in different parts of the lens to expand one’s range of vision to see objects clearly at all distances without glasses or contact lenses. Multifocal lenses can reduce the need for reading glasses. However, multifocal lenses can result in unwanted visual effects, such as glare, haloes and reduced colour contrast. These effects make them not a preferred option in many cases.
The newest and probably the best intraocular lens option is the recently available Extended Depth of Focus (EDOF) intraocular lens. In some ways this is like the traditional multifocal lens: EDOF lenses allow a large range of vision for distance and intermediate activities (but eyeglasses still might be required for very close activities and fine print reading). However, by their clever design they achieve this without all the visual problems of multifocal lenses – they are as well tolerated as monofocal intraocular lenses.
Clearly there are many options available and no one-size-fits-all solution. It is important to have a frank and open conversation with your cataract surgeon about your visual needs, lifestyle and goals; understand the necessary tradeoffs for each option to come to the right decision for you.