Eye conditions
Sight is such a crucial aspect of our life that we should do everything we can to safeguard it. Consequently, it’s important to be familiar with the symptoms of common eye problems, just as it is with any other medical issue, so you know what to look for, what to do and when to get care. Your eyes can also reveal indicators of more serious problems with your overall health, such as diabetes and high blood pressure. Since the symptoms of these conditions are not always visible, frequent eye exams are an important component of staying healthy.
Normal vision
For perfect clear vision, what we see (an image) needs to be focused onto the retina, just like a camera has to be focused properly to take a clear picture. If the image is not focused exactly on the retina, then the image will be blurred, just like an out-of-focus photograph. In this case, the person is said to have a refractive error.
Refractive errors occur when there is a mismatch between the length of the eye and its optical power. These mismatches usually originate during childhood, when the eyes are growing. The exact causes of refractive errors are still being studied, but it is known that both hereditary and environmental influences can affect their development. Most people have some refractive error, but in most cases, the error is small and does not cause any problems. Above the age of 40, it is normal for the near reading vision to become slightly blurred. This is due to presbyopia.
Colour vision deficiency
Colour vision defects are almost always inherited, although some forms can be an acquired condition as a result of some diseases or injuries. The abnormality is sex-linked, recessive, and carried on the X chromosomes.
Males have one X chromosome and females have two. In relation to colour defects, this means that any males that have a defect on their one X chromosome will exhibit a colour vision defect, while females must carry the same type of colour vision defect on both their X chromosomes to be colour vision deficient. If females have it only on one X chromosome, they will carry the condition but still have normal colour vision themselves.
In the general population, about 8% of males and 0.5% of females have colour vision deficiencies. Almost all colour deficient people do see a large range of colours, but they will have difficulty identifying particular colours. The most common defects lead to confusing certain shades of red and green, for example.
As children, few of these people will be aware that they have a colour vision deficiency, but the detection of these problems is important, especially when career choices are affected.