Common Eye Problems
In this section you will find information about some of the most common problems affecting the eye, from short sight and long-sight to why you get spots in front of your eyes.
Normal Eye – Emmetropia
Emmetropia is the optical term for normal vision.
The light from an object is focused directly onto the retina forming a perfect image
An emmetropic person can see distance and close objects clearly.
Myopia
This image above shows a myopic eye. Myopia means short sight and is where light from an object forms an image before it reaches the retina. This could be because the eye is too long, or the cornea or crystalline lens refracts (bends) the light too steeply.
A myopic person has clear vision when looking at objects close to them, and blurred vision when looking at objects in the distance.
By placing a concave lens in front of a myopic eye, the image moves back to the retina so it will be clear. A myopic person can then see distance and close objects clearly.
Hypermetropia
The image above shows a hypermetropic eye. Hypermetropia means long sight and is where the image is formed behind the retina. This could be because the eye is too short, or the cornea or crystalline lens does not refract the light enough.
A hypermetropic person has blurred vision when looking at objects close to them, and clearer vision when looking at objects in the distance.
By placing a convex lens in front of a hypermetropic eye, the image is moved forward and focuses correctly on the retina. A hypermetropic person will then see distance and close objects clearly.
Astigmatism
Astigmatism is the optical term for more than one point of focus.
It occurs when the surface of the cornea or crystalline lens is not spherical. Light from an object may focus on the retina in one direction but not the other.
An astigmatic eye has curves that are steeper in one direction than the other, like a rugby ball. A normal, spherical eye has curves that are the same in all directions, like a football. An astigmatic person will have distorted vision.
Positioning a cylindrical lens in front of an astigmatic eye will refract the light in one direction more than in the other. Note how the light passes through the cylindrical lens in two different directions. The power of the lens is not the same all over. It is stronger in certain areas to compensate for the irregular curves on the astigmatic eye. When corrected, an astigmatic person will than see distance and close objects clearly.
Presbyopia
Presbyopia comes from the greek for “old sight”. It most commonly occurs when people reach the age of 40 and over.
As one gets older the crystalline lens becomes less flexible and therefore cannot change shape as easily. This means it can’t focus close images onto the back of the eye.
Color Vision
The eye can detect colors because of three chemicals within the cone cells in the retina at the back of the eye.
Each cone contains one of the 3 different chemicals and can detect one of the 3 different primary colours, red, blue or green.
The brain can then interpret these signals and we see in full color.
Spot & Floaters
Most people notice spots or floaters in front of their eyes. They are especially noticeable when looking at a plain white background and appear as grayish specks in our vision.
The vitreous fluid , the jelly inside the eye, contains small particles. These are either present from birth or are formed when the vitreous starts to deteriorate. These cast a shadow onto the retina at the back of the eye, which appear as spots and floaters.
Glaucoma
Glaucoma is damage to the optic nerve which is usually caused by increased intraocular pressure. In the eye a fluid is produced, which normally creates the pressure which keeps the eye expanded, much like a balloon. Normally the pressure is regulated by draining the fluid from the eye through a system of canals. If the drainage system becomes blocked the fluid can not leave the eye and the intraocular pressure rises. This can damage the optic nerve, which sends visual impressions from the eye to the brain, and result in impaired vision or a reduced visual field. With age it is common that the drainage canals gradually become blocked. The pressure then rises slowly, and often the person does not notice any reduced vision. If the pressure becomes very high colored haloes can be observed around lights. If the pressure rises quickly, it can result in redness of the eye, pain and dimmed vision, and often also nausea and vomiting. Other causes of increased pressure can be injury, bleeding, certain medicines, tumors and inflammation.
How do you recognize glaucoma?
If the increase in pressure occurs slowly there are often no symptoms at all. In many cases you yourself don’t notice that your vision has become worse, since you can still see clearly and since only small parts of the visual field disappear. That is why it is wise to check your vision regularly as you get older.
This is particularly important if you have close relatives who have glaucoma or increased intraocular pressure. If the increase in pressure is faster your eye may become red, you may experience aching and blurry vision, and often also nausea and vomiting. If this occurs it is important that you quickly consult a doctor and receive treatment so that your vision is harmed as little as possible.
Cataracts
A cataract is a clouding of the eye’s lens. The condition usually affects elderly, but can also occur in young people. There is even a special form of cataract that can appear in newborn babies. The cause of cataracts is not known. It may be associated with for example long term effects of sunlight, previous injury to the eye, other diseases of the eye, certain drugs or other diseases.
How to recognize cataracts
In the early stages of a cataract lights may appear blinding. Colors may be perceived differently (often yellowish), and as the lens becomes more opaque, vision deteriorates. Usually the loss of vision is perceived as gradual and slow, but some people may notice it suddenly, e.g. if one eye, the better eye, is accidentally covered. In most cases cataract affects both eyes, but when a person becomes aware of the problems one eye’s lens might be much more clouded than the other eye’s. An essentially one-sided visual impairment usually leads to problems with estimating distances, e.g. difficulties pouring into a cup or walking up or down stairs.
Conjunctivitis
The role of the conjunctiva is to produce lubricating substances for the tear film. It also contributes much like the mucous membranes of the airways to the defense against different infections. For example during colds the conjunctiva, like the mucous membranes of the nose and throat, becomes red and swollen and produces a secretion that is stickier than normal. Conjunctivitis is most commonly associated with cold symptoms, but can also appear without any symptoms of the respiratory tract.
Symptoms
Conjunctivitis usually causes soreness, burning, itching and sometimes light sensitivity. The eyes become red and there is often a sticky discharge, particularly in the morning.
Dry eyes
- When I sit in front of the computer for a long time my eyes become irritated and feel gritty.
- My eyes feel so tired and irritated nowadays. It’s at its worst when I try to read or watch TV.
Many people suffer from dry eye syndrome. The problem is more common in higher age groups, but young people can also have dry eyes. Often the discomfort is felt during certain activities for example when working in front of a screen or when reading. For most people their eyes not only feel dry but also tired, irritated or sore.
The cause of dry eyes is that the tear film (what we in everyday terms call tears or tear fluid) for some reason does not quite manage to keep the eye moist. Small injuries then occur on the eye, and that is what feels irritating and gives a foreign body sensation.
Dry eyes can not be cured, but a lot can be done to alleviate the symptoms.
Age Related Macular Degeneration
The macula is the centermost part of the eye’s retina, and the only place which provides really sharp vision. When you examine the retina this area appears yellow. Different diseases can disturb the function of the densely packed photosensitive cells in the macula. The most common damage is due to old age. The causative relationships are not quite clear, but inadequate blood circulation and/or local metabolic problems seem to be important. It is only in exceptional cases that disease’s development can be affected by lifestyle changes. Age-related macular degeneration is the most common cause of impaired vision among adults in the western world.
How does one recognize age-related changes in the macula?
Usually objects will appear fractionated, with pieces missing, the observed object may appear blurry or not be visible at all. The problems will be most noticeable when the person is reading or doing work close up. The area that surrounds the object being looked at, the periphery, will however be perceived more clearly. Changes to the macula do not cause blindness.
The ability to read may however gradually decline, although as a rule the course of this is not fast.
If also the orientational vision should decline, it is probably due to some other condition which then should be evaluated by an eye specialist.