Posts Tagged ‘cornea’

The Perfect System

Sunday, June 20th, 2010

The eye is one of the most amazing organs in our bodies. Our sight is the most precious of our senses, and these small and perfect globes make sight happen by refracting light through it’s systems to help us make sense of our world. The eye is an incredibly complex and sensitive structure, all finely tuned, so it’s not surprising that tiny abnormalities result in visual defects and lead us to need help to correct our sight.

For perfect sight, light has to enter the eye and focus on the back surface. If your eyeball is too long, you’ll be short sighted. If it’s too short, you’ll be long sighted. Specs or contact lenses position the light in the right place so you can see clearly. If the curve of your cornea, the clear window at the front of the eye, is imperfect, then this will also create a problem with focussing.

Light enters the eye through the pupil, the black hole at the centre of the eye. It travels through the crystalline lens, a transparent structure that changes shape to let us see both close up and far away. Muscles hold the lens in place and stretch and relax to alter its shape and therefore its focus. If the lens is not the perfect size and shape then this will add to the visual defect of the eye. So you can see that there are several reasons why you may need glasses or contact lenses.

Once your optical system has been corrected and is working as it should, light reaches the light sensitive layer, the Retina, which lines the back of the eye. Here the image we see is upside down and in reverse! It travels to the brain through the optic nerve, where thankfully it’s put the right way round.

Ophthalmologists and opticians are lucky in that they’re the only clinicians who can examine their specialist organ without cutting their patient open! Thanks to ever advancing screening equipment and retinal imaging systems we can see inside your eyes and spot the very first signs of problems. This fantastic and beautiful system works on our behalf for every minute of our waking day, so look after it by attending your check ups and taking a few minutes to appreciate and maintain it.


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To Wear or Not to Wear?

Wednesday, March 24th, 2010

A common question that we’re asked is one that may seem to have an obvious answer. If I wear my glasses, will it make my eyes weaker? Will I start to rely on them? Some patients are clearly so concerned that they put themselves at risk by leaving their specs off unless they absolutely have to wear them.

So, why do we need glasses and how do they work? Put simply, you are short sighted if your eyeball is too long, and long sighted if it’s too short. Light is focused in front or behind the retina and your sight is blurred. Some visual defects are also down to irregularities in the surface of the Cornea, the clear area we look through at the front of the eye.

So, as the reason for your sight defect is physical, wearing glasses or leaving them off will not change your sight. All that happens is that your brain realises that life is easier with the specs on, and you get used to seeing clearly. This makes you feel reliant on them, but if you left them off for a day or two this effect would be lost.

At best you’ll get a headache if you don’t wear them, which will quickly improve once you put your glasses back on. At worst you could cause an accident by not seeing clearly and failing to react. Never drive without your specs if you’ve been told you need them to reach the driving standard.

Keeping your glasses on your face, where they belong, will keep the frame in good condition, and save any eye strain. They’ll always be there when you need them, and you’re utilising the gift of sight at it’s maximum standard. The good news is that leaving them off will not make your sight worse, so don’t panic if you do feel more comfortable under some circumstances without them on, it is allowed as long as you’re not behind the wheel!

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High Power Solutions

Wednesday, February 24th, 2010

Those amongst the population who have normal vision have no idea how debilitating it can be if you are very short or long sighted. While most visual defects can be corrected with specs or contact lenses, none of the options is perfect, and then you have the problem of your sight without your correction in place. What if you wake up in the night and can’t find your specs? What if you break your only pair? What if you get an eye infection and can’t wear your contact lenses? Most patients with high prescriptions will at some point have had the heart stopping experience of having to manage without their glasses. So what are the other solutions?

A first step for many is contact lenses, and within that long term wear lenses. Disposable lenses that can be worn overnight are not new, but as new materials are developed they are available for more patients and with many different options. The joy of waking up in the morning and being able to see is the gateway to a whole new world if your sight is very bad, and extended wear lenses are an excellent choice for more and more patients. Speak to your optician, but always adhere strictly to their wear guidelines and keep up to date with check-ups.

A more permanent option is surgery, either Laser surgery that changes the shape of your eye to correct sight, or an implanted lens that goes inside your eye to give you the correction you need. Neither is for the faint hearted, but with clinics springing up all over the country and prices coming down, the surgical route is one that is becoming more popular. Today society is generally more accepting of elective surgery, and compared to Botox or a Boob job this is a necessity! Either type of surgery does have  limitations, and you have to go through examination and counselling before you can go ahead. The shape of your eye, thickness of your cornea and prescription may limit your choices, and a good surgeon will discuss all of this with you before you commit yourself. You also need to know recovery time, expected results, and cost before signing your sight into their hands! For some patients full correction cannot be guaranteed, and you may still need glasses at certain times. A reduced prescription or specs just for close work may however make a massive difference to your lifestyle, so don’t dismiss this idea without thinking about it. If your poor sight is a disability then maybe it’s time to look at more drastic measures than new specs!

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UV and Your Eyes

Saturday, May 16th, 2009

What Is UV Light?

UV or Ultra Violet light is an invisible part of the spectrum of light that surrounds us. Due to the increased incidence in skin cancers, we know about the damaging affect of UV on our skin, but do we think about the fact that UV can also damage our eyes?

UV is made up of three wavelengths of light

  • UVA- closest to visible light, range 320 – 400 nanometers
  • UVB – 280 – 320 nm
  • UVC – 280 – 200 nm

Could UV Damage My Eyes?

UVA and UVB can cause significant damage to the crystalline lens inside the eye and to the retina. It’s also harmful to the cornea – the transparent window at the front of the eye.

UVA is the most dangerous, especially if you are exposed to low doses over a long time. It can damage the eye but it is absorbed by the crystalline lens. This protects the retina but as the affects accumulate pigments are generated within the lens, and with ageing and further exposure cataracts develop. When cataracts are surgically removed that vital filter to protect the retina is gone.

UVB causes sunburn and snow blindness, and this is exacerbated by reflection from water and snow. The cornea absorbs it to protect the internal structures of the eye, but that does leave the cornea vulnerable to problems. Pterygium is a patch of cloudy tissue that grows on the cornea as a result.

UVC is filtered out by the ozone layer, but if you’re in an area where the ozone layer is thin, then it may still be dangerous.

Do I Need UV Protection?

Yes, if any of the following applies to you:

  1. You spend time on the water.
  2. You’ve had cataracts removed.
  3. You spend most of your time outdoors.
  4. You like wearing dark glasses.
  5. You’re regularly exposed to UV light.
  6. You live where the ozone layer is thin.

What Will Protect My Eyes?

Wearing spectacles, whether dark or clear gives you some protection against UV, but total protection only comes from a UV Filter or a Polycarbonate Lens. Other lens materials give varying degrees of UV protection.

Standard Plastic – As these lenses can yellow over time manufacturers add a small amount of UV filter to the material. They give about 92% UV protection.

Glass – As they do not absorb any UV they give no protection.

Lenses that darken in the sun – these lenses go dark due to UV light, so as they change they block all UV.

UV filter – This is a lens coating which guarantees to give 100% protection against all types of UV.

Sunglasses are sometimes labelled as giving protection against UVA, UVB, or UVC. The problem with listing these categories is that we see the UV symbol and assume we are protected. You need to make sure that the lenses in question filter all types of UV.

Do I Need A UV Filter On Sunglasses?

Our eyes react to bright light by reducing the size of the pupil. This stops light from getting to the retina and the lens. So a tinted lens will let light flood into the eye, and without a UV filter the internal structures are fully exposed to the dangers of UV.

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