Cataract is the leading cause of blindness worldwide. The numbers are truly enormous. Approximately 20 million people worldwide are blind from this, with 400,000 people becoming visually disabled every year from the United States alone. Unsurprisingly, the most common day case procedure in the world currently is surgery to remove the opaque lens and to replace it with a clear, synthetic intraocular one. It is a major global health issue, particularly for developing countries where there is poor access to eye healthcare.
So what exactly is a cataract?
A cataract means a cloudy or opacified lens. The lens is the middle window which separates the front (anterior) and back (posterior) segments of the eye. In a normal eye, it focuses any light entering the eye onto the retina. The retina is the innermost layer of the eye which converts the light into biochemical signals which are subsequently transmitted to the brain.
As you age, your lens becomes gradually more opaque. This affects the amount of light that is focused onto the retina. Your eyesight gradually becomes more blurry and your visual acuity decreases. The more severe the lens opacity, the less light enters the eye and the less the eye sees. Another disabling effect is glare, especially at night. An increase in myopia may occur when the lens becomes denser and thicker. Sometimes, it may also cause the perception of double vision even with the other eye closed.
Left: In a normal eye, light is focused by the clear lens onto the retina to obtain a crisp image.
Right: Light passing through a cloudy lens does not focus well on the retina, and so a blurry image is obtained. The scattering of the light entering the eye also causes the troublesome symptoms associated with glare and reduced contrast sensitivity.
What causes cataract?
Unfortunately, age is the most common culprit. This means that your lens will gradually become cloudy as you grow older, despite how much you may want to protest against it. As you age, the lens tissues no longer function as efficiently, leading to buildup of oxidants and insoluble proteins in the lens. The combination of oxidation damage and protein accumulation is thought to cause the lens to become cloudy and opaque.
This picture shows a lens that has undergone significant clouding and has become very dense. Very little light is able to enter the eye and it is therefore unsurprising that this eye is virtually blind. It can only see vague shapes and shadows. Vision can only be restored with an operation to remove the opaque lens.
Lifestyle changes, diet and nutritional supplements may therefore play a part in preventing or at least slowing down the aging process in the lens. However, there is nothing you can do that will 100% protect from lens clouding.
Aging is not the only cause of lens opacities. You can be born with congenital cataract. It can also occur with other eye diseases or general health conditions. Associated eye diseases include acute angle closure glaucoma, keratoconus, and uveitis. General health conditions linked with lens clouding include diabetes mellitus, high blood pressure and genetic conditions such as Down syndrome.
Essentially, anything that can disrupt the local lens environment will likely cause the lens to become hazy. Eye surgery, such as glaucoma surgery and retinal detachment surgery, usually results in cataract development within 1 to 2 years. Steroids (even in creams, inhalers and nasal sprays) and contraceptive pills are also associated with opacification of the lens.
How is cataract treated?
There are various types of lens opacities (nuclear, cortical, posterior subcapsular, mature, Morgagnian, familial, and so on), depending on how they look on examination. However, the principle for the treatment of all types is the same. There may be slight differences in technique, but these are minor and do not affect the outcome of surgery.
The 3 main types of age-related lens opacities. Treatment with surgery is essentially the same for all 3 types, although the technique may vary slightly.
At present, the only proven effective treatment is with surgery and intraocular lens implantation. This procedure is minimally invasive, requires only a small incision and has quick postoperative recovery. The success rate of phacoemulsification surgery is at least 98% in many centers.
Sounds great! But can anything go wrong?
Yes, it can.
However, cataract surgery complications are uncommon and occur in only around 2%. Most complications (including high intraocular pressure, cystoid macular edema, subconjunctival hemorrhage) are not serious and will settle over a few weeks if treated appropriately. Occasionally, a second operation is needed to fix problems that occurred during the phacosmulsification surgery.
Severe complications (such as retinal detachment and severe infection resulting in blindness (endophthalmitis ) are very rare (less than 0.1%). Advances in surgical techniques and intraocular lens technologies mean that surgery can be performed earlier with less complications and with increasingly better visual outcomes.
Severe infection after surgery, also known as postoperative infective endophthalmitis, is one of the most dreaded complications following phacoemulsification surgery. Prompt treatment with antibiotics and steroids is necessary to save the eye from blindness.
(Image adapted from the internet)
However, not everyone is comfortable with the idea of having surgery. Some would prefer to try to prevent, or at least delay, the cataract from getting worse before considering an operation. Much has also been written about possible alternative treatments for cataract, but these have not been studied to be effective over the longer term. Consult your local ophthalmologist if you wish to consider other ways of managing without having to undergo surgery.
