Common Defects and Diseases of the Eye

You may need clarification of some eye diseases and defects, if you did not get the chance to talk to your Optometrist about them! Some simple explanations below:

Myopia (Short Sightedness)

If your sphere part of the prescription has a minus sign, then you are short sighted, which means you can see clearly close too, but less clearly far away.

Hypermetropia (Long Sightedness)

If your sphere part of the prescription has a plus sign, then you are long sighted, which means you have to make more effort to focus at any distance without your glasses on. This problem worsens with age.

Astigmatism

Astigmatism is a common eye defect, and is simply corrected by your prescription. This is the cyl or cylinder part of your prescription. It means that the front surface of your eye is shaped like a rugby ball, rather than a football, so you need a correction for the shorter curve of the rugby ball, and a different correction for the longer curve. It may be in one or both eyes, and can come and go.

Presbyopia

Presbyopia literally means ‘old eye’, and it refers to the problem of not being able to see close to as we get older. From birth, the lens inside your eye changes shape, and therefore power, to enable you to see at all distances. Unfortunately it hardens as you get older, and as it becomes less flexible you won’t be able focus close too. It can become noticeable at any age after the early forties, and will progressively get worse as you get older. It happens to everyone, and nothing can be done to prevent it! Initially, holding things further away will help, but if the light is poor, or you’re tired, fine detail will become a strain. At this point, you’ll need a separate prescription for reading

Cataract

A cataract is basically loss of transparency of the crystalline lens within the eye. The delicate protein fibres within the lens change – rather like the process of cooking an egg white! Cataract never causes complete blindness, but as transparency is lost, the patient will lose clarity and detail. Most cataracts occur in elderly people, as cataract is an ageing process. It is easily corrected with an artificial lens, which is implanted in the eye, usually as a day case. Rarely, cataracts can also occur as a result of injury to the eye, or as congenital cataract, present from birth.

Conjunctivitis

The conjunctiva is the transparent membrane that covers the sclera (white of the eye) and lines the inside of the eyelids. Inflammation of the conjunctiva causes redness, discomfort and discharge. The most common causes are infection and allergy. Drops and/or ointment are normally prescribed. Optometrists are able to prescribe antibiotic drops in emergencies only. Contact lens patients should be made aware that their lenses should not be worn during the course of an infection.

Corneal Abrasion

A scratch or defect of the cornea, which can be caused by a small sharp particle in the eye or by injury – for example a twig or hair brush. They usually heal quickly, but meanwhile cause severe pain, photophobia and increased production of tears. Pain may be relieved by analgesics, and antibiotic drops are usually given to prevent any risk of bacterial infection.

Detached Retina

The retina is the light sensitive layer that lines the inside of the back of the eye, containing specialized nerve cells. In cases of detached retina, it separates from the back of the eye. This can be the result of injury, but more often it occurs spontaneously. It is more common in very shortsighted people, who have thinned retinas with areas of degeneration. This condition is painless, the first symptoms are flashes of bright light at the edge of the field of vision, accompanied by floaters. Symptoms do not however always occur, and the first indication may be a black ‘drape’ obscuring vision. Prompt medical attention is vital. If the macula (site of central vision) detaches, then normal central vision may never be restored. An ophtalmologist at the hospital will usually repair the retina surgically.

Diabetic Retinopathy

This is a complication of diabetes, occurring when new blood vessels form on the retina, damaging it and causing loss of vision. Laser treatment is required to seal the blood vessels, but this may however destroy the nerves in the treated area.

Floaters

Floaters are fragments that patients can see floating in their field of vision. They move rapidly with eye movement, but drift slightly when the eye is still. They do not usually affect vision. They are usually shadows cast on the retina by particles in the vitreous humour, a jelly like substance behind the lens. A sudden appearance of a cloud of dark floaters can suggest retinal detachment. A large red floater that obscures vision is usually due to vitreous haemorrhage.

Glaucoma

A condition in which the pressure of the fluid in the eye is so high that it causes damage. The excessive pressure compresses and obstructs the small blood vessels that nourish the optic nerve, resulting in gradual loss of vision. The most common form is chronic simple glaucoma, which rarely occurs before the age of 40, runs in families, and often causes no symptoms until blindness is advanced. It is usually controlled with drops, but if this fails, surgery is performed to open up the drainage channels, or to create a new channel. Acute glaucoma occurs if there is a sudden obstruction, and pressure rises quickly. Symptoms include pain, fogginess of vision, haloes around lights and nausea. This is a medical emergency and requires urgent treatment. Pressure is controlled and surgery is then performed. Glaucoma can also be caused by injury to the eye, and as a congenital condition due to structural abnormality of the drainage channels.

Migraine

Vision may be affected in some cases of migraine, creating expanding areas of blindness surrounded by a sparkly edge, which can increase to involve up to one half of the field of vision of each eye. This blindness usually lasts for around fifteen to twenty minutes, and is often associated with headaches, and/or nausea. It can affect one eye or both.

Subconjunctival Haemorrhage

Bleeding which occurs under the conjunctiva. The small blood vessels here are fragile, poorly supported, and often leak. Bleeding may occur spontaneously, or after coughing or vomiting. It is usually harmless, although it looks dramatic! The blood usually disappears without treatment after 10 to 14 days.

How to keep your eyes healthy

• Most importantly – have regular check ups with your Optician
• Always wear good quality sunglasses with full UV protection
• Eat a good and varied diet, rich in vitamins and minerals. You could also consider taking an eye health supplement.
• If you’re using a computer, take regular breaks to give you eyes a rest.
• If you wear contact lenses, follow your optician’s guidelines rigidly, for hygiene and wearing times.
• If working in a risky environment, whether home, garden or work, wear the correct protective eyewear.
• If medication seems to be affecting your eye sight, tell your Doctor immediately
• Stop smoking! Smoking had been linked to cataract and Age Related Macular Degeneration.
• Don’t rely on work eye screening, or checking yourself over the counter. Your Optician can tell you so much more than whether you need glasses. He could save your sight or even your life
• Take regular exercise as it improves the oxygen supply to your eyes.