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The eye

The eye is a fluid filled ball (vitreous gel) held inside the eye socket by delicate muscles, which control eye movement up, down, left and right. At the front of the eye is the cornea which helps you focus. (People who wear contact lenses place them on this part of the eye). Behind this is the iris which controls the amount of light entering the eye. In its centre, a small aperture (the pupil) widens to let more light in when it’s dark and narrows when there is bright light. A circular ring of muscle surrounding the iris relaxes and contracts changing its shape to provide additional focus. Light then passes through the fluid in the eye ball to the retina at the back where millions of sensitive cells convert light into nerve impulses. These are sent to the brain where images – including the words you’re reading now – are assembled into stuff you can understand.

Tears

Tears keep the cornea and conjunctiva (which covers the white of the eye and the inside of the eyelids) constantly moist. Blinking sweeps a film of tears across the eye, keeping the surface well lubricated and washing away dust and dirt. In addition to salty water, tears contain a natural antiseptic. Tears drain away through a single hole near the inner end of each eyelid into small tear sacs and then down through the nose which is why your nose runs when you cry.

Short and long sightedness

Short sightedness is when near objects can be seen clearly while objects further away (even by as little as 30cm) can appear blurred or indistinct. Short sightedness is usually caused by the eye being too long front to back (horizontally) and, as a result, images of distant objects focus just in front of the front of the retina. Conversely, long sightedness is when the eye is too short affecting your long distance vision. These conditions are usually treated with glasses or contact lenses and regular check-ups for this and other sight conditions is essential – even if you think you have 20/20 vision.

Contact lenses

Contact lenses have been around for just over 100 years, although Leonardo da Vinci was actually the first to describe the possibility of using them over 500 years ago. While there are different types of lenses, soft lenses tend to be the most popular because they are easy to wear from the start, but an optician will be able to recommend a lens best suited to your needs. The high water content in soft lenses (40-80%) allows more oxygen to reach the eye covered by the lenses and so they can be worn for longer periods. However, despite their obvious success, problems can occur such as:

• Eye infections through a failure to keep lens maintenance equipment clean, wash hands thoroughly before putting in/taking out lenses, and keeping lenses properly disinfected
• Sensitivity to the lens or maintenance solutions
• Using lenses for extended periods of time
• Hard lenses that scratch the eye if they’re put in roughly or are worn for too long
• Problems with tear production
• Sleeping in lenses particularly after a long night out when you may be dehydrated. You sometimes have to peel the lens off the eye. This is not good.

Symptoms include:

• Redness, stinging and a sensation of heat in the eye
• Pain or prickliness in the eye
• Lenses jumping around the eye
• Increased mucus leading to cloudy or foggy vision

If you experience any of the above, stop wearing your lenses immediately and head straight for your optician or GP.

Conjunctivitis

Conjunctivitis is an inflammation of the eye causing a range of symptoms including redness, discomfort, discharge and a sensitivity to light. Most cases are caused by bacteria which are spread from hand-to-eye contact or by viruses (eg: cold or sore throat). However, an allergic response can also be caused by contact lenses and associated cleaning solutions, pollen and cosmetics.

While warm water will wash away the discharge and remove any crusts on the eyelids, the infection itself usually requires treatment with eye-drops or an ointment containing an antibiotic, antihistamine or cortico-steroid drug. The important thing to remember is to see your optician or GP as soon as you think you have a problem. (This doesn’t mean making an appointment in a week’s time.)