The back of the eye is called the retina; this works like the film in a camera. Both the cornea (the transparent front window of the eye) and natural crystalline lens act like the lens in the camera. When light is focused and hits the retina, an image is taken and sent to the brain.
When you are young, the lens in the eye is elastic and moves very well. This movement is called accommodation and is comparable to the autofocus function in a camera. Accommodation enables you to read the small print as well as see distant objects comfortably. As you age, the lens loses its elasticity and is no longer able to see small print. You will typically notice this at around the age of 40 and above.
Most people, when faced with this challenge, begin to use reading glasses. The power of reading glasses must increase with increasing age. However, there is a limit. Eventually, when the lens loses its elasticity, it begins to opacify (cloud over) and lose its clarity. This typically occurs when you are around 50. At this stage, you might start to lose some contrast sensitivity and the ability to see vivid colours. A cataract can develop in both eyes and can vary in their developing between the two eyes.
Types of Cataracts include:
An age-related cataract is the most common cause of blindness. Cataract formations occur when the natural crystalline lens inside your eye becomes cloudy or misty. It may feel as though you are looking through a dirty camera. Developing a cataract is a part of the natural ageing process along with presbyopia (the loss of close-up vision). An age-related cataract usually occurs in those over the age of around 60, it can happen in one eye or both your eyes and tends to get progressively worse with time.
A traumatic cataract
Traumatic cataract can appear when there is damage that affects the natural crystalline lens. Damage is usually a result of an eye injury. This kind of cataract can impede the vision in the same way. We can remove it with surgery.
Congenital cataract has the potential to lead to blindness and irreversible damage to the visual system if not addressed within 6-8 weeks of birth. Cataracts in new-borns are rare and affect 3-4 per 100,000 children in the UK. It accounts for 5% to 20% of blindness in children worldwide.
A developmental cataract
A developmental cataract starts at a young age and can progress to become visually significant enough to require surgery. Any cataract or lens opacity that is present in a child less than 12 years of age could lead to permanent loss of visual potential in the affected eyes unless treated. Sometimes, we use occlusion therapy by patching the unaffected eye to sufficiently stimulate the eye affected by cataract. Surgery ultimately becomes necessary.
A secondary cataract
A secondary cataract develops at any age and is usually the consequence of a disease, irradiation or medications. Glaucoma and diabetes are known conditions that contribute to cataract development. Steroids are one of the medicines that are known to cause a cataract, mainly posterior subcapsular cataracts (a type of cataract where the opacity lies along the back surface of the lens). Diabetes control can slow down the progression of cataract, but we cannot reverse cataract development. At this stage, surgery becomes the only option.