Cataract basics you should know
Many of us will develop cataracts. In fact, all of us will do so if we live long enough. It is an unavoidable effect of age and is eminently treatable.You may start to appreciate the presence of lens opacity within one or both of your eyes from around about the age of 60 years. The opacity can cause a change in your glasses prescription. Or you may find that you are getting glare when driving or poor vision in dim light or clouding when looking at the fine detail. A cataract can be barely perceptible, and it progresses very gradually and insidiously.
What happens when you have a cataract?
The lens of the eye develops a cataract when it starts to cloud. This change is part of the regular ageing process but cataracts can have other causes as well, such as trauma, taking steroid tablets for a long time, having had inflammation in the eye or they may be congenital. Normally, your eye lens is quite flexible when you are young. Lens flexibility is useful because it can change shape and accommodate to enable you to focus on close objects and see fine detail. The ability of your eye lens to be flexible diminishes with time, and sometime after the age of 40 you may find that you have trouble with reading and start to require reading glasses, but that is not a cataract. This effect is an age-related tiredness of the eyes called presbyopia. Presbyopia is an age-related vision change which happens to virtually everybody unless they have got a small amount of short-sightedness in which case it also happens to them, but they get around it by taking short-sighted glasses off and looking at the near object without any glasses at all, using their focal point. Therefore one of the most important things when you see an ophthalmologist it is for them to assess whether you have a refractive error, whether this is due to presbyopia or other, or whether your visual disturbance is in fact due to an early cataract. We liken the anatomy of the eye lens to that of an onion, where we can find lens fibres arranged concentrically. These fibres are transparent crystalline lens fibres, and the lens is about the size of a smallM&M or Smartie. Your eye lens is behind the coloured iris, in line with the centre of the pupil. See the diagram –
Normally in youth and young to middle-aged adults the eye lens is quite clear and transparent. It can gradually get a small yellowness to it, which is more noticeable in smokers. Yellowing of the eye lens also occurs with hardening of the central part of the lens.
Are there different types of cataracts?
The lens has three main parts:
- An outer layer, which is a thin clear membrane layer called the capsule, like the skin of a peach.
- This outer layer covers the soft clear layer called the cortex, which is like the fleshy fruit of a peach.
- The firm centre of the lens is called the nucleus, which we liken to the likened to the peach pip.
If the nucleus starts to go a little yellow or a little dense, we call it a nuclear cataract. If the cataract is in the cortex, we call it a cortical cataract. If the cataract is in or under the capsule, we call it a sub-capsular cataract either an anterior one or more commonly a posterior one. See the diagram –These distinctions in the type of cataract are incredibly important, and your ophthalmologist will help diagnose whether you have a cataract, and what type of cataract it is, depending on its appearance and location within your eye. Whether your eye has a nuclear cataract, a cortical cataract or posterior sub-capsular cataract, each one of these will give different visual characteristics. In the forthcoming series of blog posts, I am going to talk to you about the causes of the cataract, the symptoms you may experience, what happens when you have your assessment by the Clinica London cataract specialists, Ms Laura Crawley and Mr Jaheed Khan. I will then go on to talk about what surgery we can do and how you can prepare for that. I will tell you about what happens on the day of surgery and then the post-surgery course. I will also say more about Laura and Jaheed, their skills and love of cataract surgery.