Leonardo Da Vinci wrote in his diary “this is the eye, the chief and leader of all others” (1500s). Da Vinci explored the notion of the eye as an optical instrument, and his conceptual search for the science behind sight eventually gathered material momentum with the aid of his various successors: the Camera Obscura came into being a century later, powered by nothing but sunlight and a biconvex lens.





In some sense, this ancient contraption is a scaled-up simplification of the human eye. It is an optical device that projects an image of external surroundings onto an internal blank screen. Light passes through the pinhole, and the biconvex lens flips the image 180 degrees. Colour and perspective is preserved, and in turn, projected onto a screen on the other side of the room. Think of the dark box-room as the interior of an eyeball, and the screen on the back wall as the retina.


Invented by an artist, and used by artists, the camera obscura is essentially a practical extension of the human eye, designed to enhance detail and map reality directly onto paper. Once in circulation, the camera obscura underwent a variety of alterations. In order to aid drawing, it was reduced to the sizeable convenience of a box, in which a mirror re-reversed the image.






Throughout its various stages of development, its slight alterations have given rise to a plethora of charming names: Mozi’s “Locked Treasure Room” or “Collecting Plate” became Gaspar Schott’s “Magic Lantern”, and by the 18th Century, it was known as Conte Algarotti’s “Optic Chamber”.



It persists in Modern Culture; in February earlier this year, a model was installed in the New York Public Library. The Oakes brothers, dubbed “The Perspective Twins”, are conducting an exploratory journey into the origins and mechanisms of sight, specifically bifocal visual perception. Their investigation aims to detail the spherical distortions dictated by the curvature of the eyeball.   



If this hasn’t convinced you enough of the wonders of the human lens and its purposes in the field of photography, go and have a listen to the delightful band “camera obscura”, whose name pays homage to this ancient wonder.


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Our expert paediatric orthoptist Rudrika Joshi-Borrel tells us all about vision development in babies:



Did you know that almost all babies are long sighted when they are born? In most cases the eyes will correct themselves within 2 years, in a process called emmetropization.




As an orthoptist, I am a specialist in helping people with squints and similar eye conditions. If I am examining a 2 year old child, glasses are not always necessary due to the commonality of long-sightedness. On the contrary, short-sightedness in children of this age is much more unusual. Read more about long and short sightedness in our blog: "What are myopia, hypermetropia and astigmatism?”



Emmetropization is when the eye’s process of aligning its axial length to the focal length of its optics; however, imperfect alignment causes short-sightedness, and both genetics and environment can have an impact upon this process. For example, there is strong evidence to suggest that children who less time outside are more at risk. (refer below for the studies). When emmetropization doesn’t happen, light entering the eye isn’t properly focused on the retina and so the brain receives a blurred image. A secondary effect of this is that neural pathways in the brain responsible for sight start to get ‘lazy’, thus working less effectively.



An eye test, called a refraction test, needs to be done in this case as this measures which prescription lenses the child will need in order to correct their sight. If the child is given the right prescription, their vision be immediately corrected whilst wearing the glasses, and refractive adaptation will begin. So wearing glasses can actually exercise the visual system in such a way that the eye and brain eventually adapt to self-correct the child’s sight.


The more often a child wears their glasses the more adaptation occurs.There is a bit of neuroscience behind this; because the brain now receives a clear image from the optical nerves the visual pathways in the brain are stimulated to work properly. This reawakens the neural pathways.






Refractive adaptation does not always completely restore perfect vision, but does much to significantly improve it. Depending on the length of time the child’s vision has been left untouched, treatments such as occlusion may well be needed in order to further stimulate the cells, so the earlier the better. Research shows that a full 18 weeks with glasses is the maximum potential time period for refractive adaptation to have an impact, before occlusion is necessary.


Glasses make up for the miscalculation between the lens and the size of the eye; however, this will only slightly change as a child grows, as long as the prescription is very small. In these cases, the optician may advise them to wear their glasses as teenagers when at school, work, the cinema and whilst driving. For children under the age of 10, however, it is advisable to wear glasses full time.

The coordination of eye movement develops after birth once a baby sees for the first time. Whilst this development progresses it can be normal for babies to look slightly cross eyed up until about 6 months of age.



Naturally if you’re a parent you might be concerned by this, especially if it continues beyond 6 months. If you’re a bit worried, seek medical advice at the GP. If a problem is spotted then the GP may refer your child to a paediatric ophthalmic (children’s eye specialist), like My iClinic. From there a proper diagnosis and treatment plan can be made by a doctor if necessary.



If you are wondering who do you need to see, here is a list of specialists and what they do in the eye world:

Opticians and Optometrist specialise in glasses and eye tests, prescribing glasses and may detect eye diseases.

Orthoptists specialise in the non-surgical diagnosis, such as the management of squints, amblyopia and eye movement disorders, isolated and secondary to systemic disease.? Ophthalmologists are the medically trained doctors and surgeons specialised in the diagnosis and treatment of eye diseases and disorders. They can also perform “refraction tests” and prescribe glasses.


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Often people say ‘I am long-sighted’ or ‘short-sighted’, but for a lot of us who don’t wear glasses sometimes it’s difficult to understand what this means.


Fancy long and complicated words like myopia and hypermetropia make this all the more confusing.



Does short-sighted mean you can see things up close or you can’t? What makes a person long-sighted? How can glasses, lenses or laser eye surgery correct this? We can help you find the answers to these questions!



Short sighted or long sightedness occur when a person’s lens cannot focus light entering the eye in the right way on the back of the eye, also known as the retina.



If you are short-sighted (also known as myopia) you can see things that are up close, but can struggle to see things further away. This is because light entering the eye is focused in front of the retina, when it should focus on the retina. It focuses too soon. This happens for two reasons: either the lens focuses light too strongly or the eye is too ‘long’ meaning the retina is too far away from the lens. To correct this we give short-sighted people lenses that change (diverge) the way light enters the eye so once it is focused by their natural lens it focuses on the right place of the retina. These types of lenses are called minus, hence why short-sighted people get ‘minus prescriptions’.



Long sighted (also known as hypermetropia or hyperopia) is when you cannot see things up close. It’s exactly the opposite problem to short sightedness. This happens when light entering the eye is focused behind the retina; you can think of it like the eye focuses light too late. This happens when either the eye is too short and the retina is too close to the lens, or when the lens focuses light too weakly. To correct this we give long-sighted people lenses that converge the light that enters the eye so once it is focused by their natural lens it focuses on the right place of the retina. These types of lenses are called plus, hence why short-sighted people get plus prescriptions’.



Another term that we hear quite often when talking about disorders of the eye is astigmatism. It is caused by abnormalities in the cornea and the lens. Astigmatism can be described as the condition when the front of the eye is not a perfect round shape like a football, instead it is more oval like a rugby ball. This gives the front of the eye an asymmetric curvature so light scatters as it goes into the eye. This produces a jagged and slightly distorted image.

Some people are unlucky enough to have astigmatism as well as long or short-sightedness. Luckily short-sighted and long sighted don’t often happen together. But some people when getting older may get one eye short sighted and another one long sighted. Optometrists may leave these patients with uncorrected vision if they feel comfortable and would find glasses an inconvenience.



Fortunately, the wonders of modern medicine and technology mean there are many amazing ways to correct long or short sightedness! Glasses can be a low cost and even stylish solution, contact lenses although not always ideal can be a practical one. But there are even more exciting and amazing ways that vision correction can done now.

At My-iClinic our specialists are experts in two types of procedures that can cure long or short sight and astigmatism: laser eye surgery or refractive lens exchange. You can read more about these procedures on our website.


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Spring is just an absolutely lovely season: the temperature gets higher, the green gets greener and the flowers are blossoming. With all this amazing things happening around us there is going to be a number of people that will continually complain. As with the arrival of spring your eyes became: watery, itchy, red, and uncomfortable - in one word they are allergic.


Allergies are classified in three categories:

1. Mild allergy

2. Seasonal allergic disease known as hay fever

3.Vernal keratoconjunctivitis – more severe and could be all year round with allergies to house dust mites and pollen. These people tend to have severe general allergies and are called “ATOPES”. Systemic allergic signs and symptoms would include: Eczema, Asthma which tends to get worse with seasonal allergy in the spring/summer. In severe atopies, it is advisable to see an allergist. The general advice is usually to avoid exposure

Known as allergic conjunctivitis or hay fever, this reaction of the body is an inflammation. The causes of the inflammation are actually the excessive reaction of the body’s immune system to the allergens in the environment. As during spring time the nature revives. And with this new life the nature is bringing in the air a lot of particles (usually pollen which guarantees reproduction.)

Because a lot of our patients asked us about natural remedies to solve this issue, we decided to write a useful blog revealing our medical expertise.

Unfortunately we need to inform you that there are no home remedies, which will be able to eliminate the symptoms of the allergic conjunctivitis.  All the remedies that we are going to list would rather help reducing the amount of allergens that come into contact with the eyes than actually cure you. 

Our first advice is to reduce the direct contact with the allergens: one of the solutions for it can be by staying at home for weeks until the season finishes, but face it we all have to work and we all need to carry on with our responsibilities, so most probably our second solution is better for you. Get a pair of protective sunglasses; there are quite a lot of options for sunglasses. Although most of them will look like googles, they will cover your eyes very well.  There are options starting with 10£ and if you are more interested in this subject you can check this article
 hereUse simple non allergic emollient face creams and avoid creams which may contain E 45.

Another action that you may take is to minimise the house dust mites: regular washing of 
beddings including mattress cover; avoid use of carpets and use hard floor as this limits the accumulation of the allergens. Change the air filters and use eco ventilation systems which filter out the pollen and house dust mite while recycling the heat.

The second advice is in case the contact with the allergens already occurred, there are a couple of solutions that you have: 

1.First you can make some cold compresses. Soak a clean face cloth in a bowl of clean chilled water and place over your eyes. You can chill the water by putting in some
 ice cubes or you can use the water from the bottle kept in the fridge.

2. Second you can dilute the pollen and the antigen in the tears with unpreserved (preservative-free) artificial tear drops. We verified many of them and can truly recommend the following drops: Hylo-forte by Ursapharm, Hydramed night by Farmigea and Xailin night by Nicox. 

However we strongly recommend seeing an ophthalmologist as soon as possible because the problem with the allergies is that you can’t treat it until you know the source of it, therefore stopping wasting time and book your appointment with the specialist.

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How do virtual reality goggles work.

Having two eyes facing forward is a great advantage. Animals that have two eyes which face forward see the some objects in each eye. But because the two eyes are separated by a small distance each eye can see the same scene but with slight differences. The two photos of the glass with the pens have been taken by moving the camera the same distance as there is between the average person’s eyes. Look closely and see that there are slight but definite differences in the spacial arrangement of the object. In the third photo I have photoshopped the two images together and you can see the intolerable double vision that would result if the brain just superimposed the two images one on top of the other.



Clearly the brain is able to deal in some way with this so we don’t see two different images superimposed. Instead in reality we get a clear 3 dimensional view of the scene. How does our brain do it?

Look closely at the edge of the blue pen nearest the camera in each of the two photos. See that in one there is greater distance A between that pen and the pencil behind than there is in the other picture with the B. When the visual cortex sees these differences it knows from an innate algorithm that the objects are arranged in space in a specific way. This algorithm can then ascribe a distance value based on the differences between the two eye images. It then can tell us, the owner of the eyes, how these objects are arranged in front of us. We can see the world in 3D. Millions of years ago such information about the immediate world was very useful swinging from one tree branch to another. Our ancestors could just look and tell exactly how far away the next branch was. A pretty important skill if you wanted to survive. When they came down out of the trees this 3D vision was a great asset in tool making and also when using those tools. I think 3D vision was probably as important as our opposable thumbs in our evolution.

           


We can create an impression of 3D by presenting two different images to the brain, one through each eye. We all can remember 3D viewers when we were children. We look though them, held them up to the light and could see Mickey Mouse or Grand Canyon as though we were there. By presenting the eyes with two separate images the brain could “do the maths” and give us the impression of 3D. These images were static but quite recently it have been possible to present moving images. The result is that we can perceive a moving scene in 3D. In 3D cinema and 3D TV there is the problem of how do we present the different images to each eye while looking at a screen far away. The crudest method is to use red/green glasses. This works by having two images projected on the cinema screen or TV. All 3D footage is shot using two cameras. These cameras are mounted together on a single tripod and are separated by the same distance as there is between the human eye, about  65mm. Therefore each camera records a slightly different image as a result. Now we put a red filter in front of one camera and a green one in front of the other. When we play the film back we project the images from each camera simultaneously onto the same screen and watch them through red/green goggles. What happens is that the eye that looks through the red goggle sees the red camera best and can’t see the footage from the green camera and vice versa. In this way the brain gets two different images with all the spacial clues to build a 3D image. Another way is the instead of red and green filters in front of the camera the cameraman can use polaroid filters. One filter is vertical and the other horizontal. Then we can view the footage through polaroid glasses so we see the footage from the vertical polarized camera with our vertical polarized glass and the other eye sees the footage from the horizontal polarized camera. And again, the brain is able to make a single 3D image from the two separate images it gets.


So, in VR goggles each eye is shown a different image of the same scene shot from a slightly different angle.  The brain then uses that data to construct a three dimensional image which we perceive as though we were really there. If you take your phone out of the goggles you will see that there are two images on the screen, each one slightly different. In the goggles your right eye sees the right image and the left sees the left image, and hey presto!


And the very latest cameras can also shot the two images in 360 degrees which means that as you move your head around and look up and down the movement sensor tracks the movement and changes the view to mimic your head movement.  And if you have read (the book is much better) or seen Ready Player One you will know that we are not far off being able to place an avatar of ourselves into that virtual world which will interact with the avatars of other people. So we could soon live another life in the digisphere.


Hearing.

A similar algorithm is used by the brain to locate the origin of sounds. We all know that we can hear a sound and tell pretty accurately where it has come from.  This is because the sound reaches each ear at a slightly different time. The ear that is nearest the sound hears it first and then the same sound reaches the other ear. The tiny time difference is used by the brain to calculate where the origin if the sound is. That’s why an animal will cock one ear toward the sound to try to locate it. By placing one ear closer to the sound and the other further away the time difference is maximised (as well as the loudness ) so that the brain’s algorithm is more easily able to ascribe a location to the sound origin. This is clearly a very important skill.



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