The Eye

“…fingerprints have approximately 40 individual features but the average iris has 256.”

What do the following celebrities all have in common? Christopher Walken, Dan Akroyd, Simon Pegg and Jane Seymour. It takes only a quick glance at the title of this article to ascertain that it must be something to do with their eyes. Well done though if you said that they all have ‘Heterochromia’, which means that each of their eyes are different colours. Regardless of whether or not one’s eyes have this rather exotic trait, these clever and intricately complex little organs tend to be a focal point and, at an individual level, one of our most vivid and emotive defining features.

They are thought to have evolved initially in single celled organisms that held light sensitive proteins. Over many millions of years, the process of ‘seeing’ became a reality through a mind-boggling transition into the eyes that we see today. Across the animal kingdom, there are many different types of eye and, as is the outcome of all evolution, the creatures they serve benefit in different ways depending on the environments in which they live.

Geckos can see colour 350 times better than us, bees have 5 eyes, most spiders have 8 and worms merely have a collective of light sensitive receptor cells. Not all eyes are structurally the same. For example, some vertebrates, including cats, have an extra layer of tissue behind the retina (the layer of cells that collects and processes light) called the tapetum lucidum. This reflects any light that has got through first time round and reflects it back into the retina again, giving rise to excellent night vision – very handy for catching unsuspecting mice. It also results in the eye-shine we see when some type of mammal is lurking in the bushes and served as inspiration for the ‘cats’eyes’ we see on our roads.

We humans must make do without these handy features and we are limited to just the two eyes. This is better than one though, as it gives us a perception of depth. To enable us to see, we must collect the light from around us and process it. Light bounces off everything (almost) and if we look towards something the light from this will hit our eyes. This light travels first through the cornea and second through the pupils (the holes made by the retractable fibres that make up the iris (the part that gives our eyes their colour). Here it hits the lens, a rounded clear organ that alters in size as we focus differently. This allows it to redirect light from different distances onto the back of the eye where the retina sits, so that it doesn’t produce a blurry picture. At the retina, the light is converted by different types of cells into nerve signals and the information is then taken via the optic nerve to the brain where it is further compiled into what we understand as ‘sight’. Interestingingly, because of the way in which the light is focused on the retina, the unprocessed image is upside down and back to front, so the brain must flip these back the right way round.

As doctors, the eyes are a useful thing to check when examining a patient because they can tell us a lot about a person’s health. Shining lights into the eyes causes the pupils to constrict and faults here can point to certain neurological conditions as can double vision and loss of visual fields. Looking at the back of the eye, we can sometimes tell if there is raised pressure in the fluid surrounding the brain, and at the front, there are characteristic appearances in or around the eyes of people who might have thyroid problems or high cholesterol. In babies, it is important to check for something called the red reflex, the normal red-orange colour of the eye when light is shone. Asymmetry here or a white reflection can sometimes point to something called retinoblastoma which is a type of cancer.

The most common eye examination one might receive is the visual acuity check. Using the Snellen charts, reading the letters on rows of ever decreasing size, we challenge ourselves to get to the very bottom level. The phrase ‘20/20 vision’ is often talked about, which essentially means we can see something at 20 metres that the average person would see at 20 metres. Outside the USA, we use 6 metres as a scale and if you wanted really exceptional vision, you would aim for something more along the lines of 6/7 (in other words you could see something from 7 metres that the average person would only be able to read at 6 metres).

If our vision isn’t quite up to scratch, we might need a correction and this is where glasses and contact lenses come in. Depending on which survey you read, between 69% and 77% of people in the UK wear glasses or contact lenses – so many that it is isn’t surprising that they have become somewhat of a fashion accessory!

More seriously, there are currently approximately 2 million people in the UK living with a level of sight loss that has a significant impact on their daily life. There are around 350,000 people registered as blind or partially sighted alone.

There are a plethora of conditions that can cause such sight loss.

  • In the UK, age-related macular degeneration is a major cause (a deterioration of the macula, a part of the retina, due either to the formation of deposits on the retina or to fluid build-up underneath the macula).
  • Diabetes is a big cause of sight impairment as well – it causes progressive damage to the blood vessels at the back of the eye and is known as diabetic retinopathy.
  • Glaucoma is a build-up of pressure in the fluid within the eye. Your optician will check your pressures by puffing air at the eye using a machine. As long as it is well controlled and monitored it can be treated with certain medicated drops.
  • Cataracts are a gradual clouding of the lens. When vision is too severely affected, surgery is an option to correct this.
  • Retinal detachment is an emergency and characteristically involves a sudden curtain of vision loss falling over one eye. It may be preceded by flashing lights and a sudden increase of floaters and needs an immediate trip to eye casualty.

Incidentally, floaters are small bits of debris that float in the eye and move around with a slight lag as the direction of gaze changes – these are common, and, except as mentioned above, are not normally something to worry about, though they can be very annoying. Unfortunately they are essentially untreatable.

As GPs, we often see a handful of more common and less serious conditions that could have been dealt with first by a pharmacist or managed at home. Red and gunky eyes most often represent conjunctivitis, while red swollen eyelids (blepharitis) or a cyst or stye over the lid can be treated with hot compresses, and a watering eye can be your body compensating for a dry eye, so try some lubricating drops. Most eye conditions do not need antibiotic treatment.

If your eye is painful however or if you are not quite sure, this must be reviewed, especially if it is red as well. There will be a local eye casualty (if you’re in the UK) that patients can call if they are unable to get to their GP. This may be where your GP refers you if they feel it needs more in-depth specialist review.

The following recommendations can help to keep your eyes healthy:

  • Don’t smoke – Unsurprisingly this causes all sorts of problems including macular degeneration and cataracts.
  • Make sure you wear sunglasses – it protects against harmful UV rays and makes you look awesome.
  • Get regular optician checks – apparently around 10% of the adult UK population have never had an eye check. Problems are not always immediately evident and so it’s best to get checked every two years at the very least, more frequently if you’re over 40.
  • Eat the right things – generally anything with lots of omega 3 fatty acids and vitamin A (also known as retinol which helps with night vision!) Examples would be oily fish, kale, spinach, peppers, oranges, broccoli and eggs.

So overall, eyes are pretty marvellous things and, more than that, they are deeply personal. One only has to look at the rising use of retinal scanning to realise just how individual they are -fingerprints have approximately 40 individual features but the average iris has 256. We only have two of them, so we must take the best care of them possible.

The Brain

While we know more than we ever have, there is still a lot to learn meaning that, in an ironic sense, the brain is still something we can’t fully get our head around.

Someone once said that if the human brain were so simple that we could understand it then we would be so simple that we couldn’t. I would have to agree. The brain is our vastly complicated seat of consciousness and individuality, controlling most functions of the body, some of which we are aware of and some of which are on a more subconscious level.

If one were to zoom in to see it under a microscope, one would find literally billions of nerve cells, or neurons, forming a continuous interconnected network signalling to each other using electrical pulses and chemical transfers. There are around 86 billion of these neurons in the adult brain, meaning that if you were to pick an area of the brain the size of a small grain of sand you might find as many as 100,000 neurons in just that one area. What’s more, each one connects to around 1,000 others via connections known as synapses.

As we zoom out again, we see that the brain has a wrinkled surface that, if stretched out flat, would cover the area of four A4 sheets of paper. It is cushioned and bathed by a viscous layer of cerebrospinal fluid that, as the name suggests, runs all the way down around the spine as well.  Weighing in at around 2% of our body weight, our brains manage around 98% of human function, which is a pretty good return. It follows therefore that it needs a fairly good power supply and, indeed, it has an important network of blood vessels that supply it with oxygenated blood and nutrients – it uses around 20% of the body’s energy supplies.

With such a complex make-up and such a plethora of responsibilities, it is no wonder that it is regarded with such intense interest and yet is still relatively poorly understood compared with other organs of the body. As with much scientific endeavour, much progress has been made in its understanding over the last century.

Take the frontal lobe for example. As part of the quest to understand the brain in more detail, scientists identify areas in accordance with their perceived function. The frontal lobe is thought to be involved in executive function such as judgement, decision-making, planning and control of behaviour – functions that became clear following an accident involving a railway worker named Phineas Gage in which, rather unfortunately, he received a metal pole through his forehead. Though he survived this ordeal, the once calm and understated worker famously showed a marked change in personality towards aggression and surliness.

Had the pole gone through his occipital lobe, he might have had trouble with his vision and, if it had pierced the temporal lobe, he would potentially have had trouble processing sound, using his memory and producing speech.

The point is that certain areas of the brain are involved in particular tasks. This can become apparent when someone has a stroke. Most strokes happen when blood supply to an area of brain tissue is interrupted.  The result can be, for example, loss of motor function in one side of the body. If there is a problem in one half of the brain, then the problem (when talking about motor function – i.e. moving an arm) manifests in the other side of the body. This is because nerve fibres from each side of the brain cross over at a certain point before descending the spine to the rest of the body.

We know that the brain performs so many functions. It allows us to move, to smell, to hear and to sense temperature. It also enables us to think. While this complexity is admirable, when it goes wrong the consequences can often be very distressing. Infection, head injury and cardiovascular disease all affect the brain’s health, as well as conditions such as Parkinson’s disease which affects the production of dopamine, (normally used to regulate our movement) and resulting in involuntary shaking, slow movement and stiff muscles.

Most significant of all, as our population grows older, dementia is becoming the largest cause of mortality in the UK and all over the developed world. Research is ongoing and we still have a long way to go both in understanding the processes involved and in treating the effects. It should be mentioned that dementia is not a single disease, rather a term to describe the symptoms that occur when there is a decline in brain function.

Alzheimer’s is the biggest cause of dementia. Though not fully understood, it is believed to be related firstly to the build-up of amyloid plaques and secondly to neurofibrillary tangles made up of proteins called TAU proteins. As more of these build up, the ability of the neurons in the brain to transmit information gradually diminishes. Research is currently focusing on the processes involved in the development of these two features. Just as importantly, the search is on for biomarkers (markers that we can sample in the blood or spinal fluid) that might give us an idea of whether someone might be developing a dementing condition, giving greater opportunity to take early steps to manage the condition and also to research disease progression over longer periods of time. Although it can be difficult to face, and often slow to present, if you have any concerns about memory, it is important to see your GP as there is often support available and it may also be the result of more benign and treatable conditions (for example low vitamin B12 levels or underlying infection).

When concentrating on the more physical effects of the brain, it is sometimes easy to overlook the deeper thought processes that are involved in our mental health. Much of our individuality comes through the environment in which we grow up. In the same way that we form new connections and synapses in our brains through repetition as we learn an instrument or practise our times-tables for example, it is thought that personality traits develop to some extent in the same way. For untold reasons, however, our minds can be fragile and depression and anxiety can be extremely damaging. Often there are so many different factors, both social and physical, that make such emotional issues difficult not only to treat but also to recognise. Chemical imbalance plays its part, for example in relation to levels of serotonin in the brain, and in such cases there can be a role for medication. More recently, there has been a push for increased awareness of mental health conditions in an attempt to remove any stigma attached to something that can cause a lot of problems if left unaddressed.

How do we look after our brains? Staying happy is a good start and there is plenty of support available for people for whom this is not the case. Keeping your mind busy helps to maintain your ‘neural plasticity’ – it ensures you are creating new synapses by learning new things. Maintaining healthy social networks is equally as important.

Regular exercise is vital for brain health as it increases the blood supply to the neurons, reduces blood pressure, helps blood sugar balance, improves cholesterol and reduces mental stress.

Getting enough sleep each night is important (8 hours being the aim).

Your diet can also give you benefits. Anything rich in omega 3 such as oily fish is useful and a ‘Mediterranean-style’ diet is a good start. Blueberries are rich in anti-oxidants, thought potentially to reduce inflammation involved in plaque formation in the brain, and dark leafy greens, such as kale and spinach, will give you good sources of vitamins C and E and folates – all thought potentially to reduce the risk of Alzheimer’s.

There is some evidence to suggest that certain people may benefit from medications like statins and aspirin but it’s always a good idea to come in to discuss any medication with your GP or pharmacist. And don’t forget not to smoke or drink too much alcohol.

While we know more than we ever have, there is still a lot to learn meaning that, in an ironic sense, the brain is still something we can’t fully get our head around.