HOYA offers a variety of tailor made lens solutions to meet all vision correction and comfort needs. No two people see the world the same way and that's why HOYA invents and designs lenses according to individual needs.
When all parts of the visual system are working, the eyes can move together, adapt to light and dark, perceive colour and evaluate an objects location in space.
A healthy eye with no correction requirements should function as per below - light entering the eye should focus perfectly on the back of the eye:
Common Eye Problems and Correction
All eyes are not the same, nor are they all perfect. They come in different shapes and sizes, some eyeballs are too long (Myopic), others are too short (Hyperopic) and some have an uneven curvature (astigmatism). One solution for correcting these problems are glasses (Ophthalmic lenses).
Short Sightedness (also known as Myopia) – Objects in the distance appear blurred (the eye is overpowered) whilst objects up close are clear.
What causes Myopia?
When light passes through the eye it falls short of the back of the eye (fovea) as seen in the below image...
Symptoms and Signs Nearsighted people often have headaches or eye strain and might squint or feel tired particularly when driving.
How to correct Myopia? The power of the eye in this case needs to be decreased therefore it can be corrected wearing concave lenses (thin in the middle and thick on the edges of the lens). If you’re shortsighted your prescription will be a minus power (-1.00), the higher the number, the stronger your lenses/correction will be.
Far Sightedness (also known as Hyperopia or Hypermetropia) - Objects up close are blurred (the eye is underpowered) whilst objects in the distance are clear.
What causes Hyperopia? When light passes through the eye it passes through the focusing system of the eye it focuses beyond the back of the eye causing an area of blur on the retina. Many children are born with hyperopia and some of them out grow it as the eyeball lengthens with normal growth.
How to correct Hyperopia? The power of the eye must be increased therefore it is corrected by wearing a convex lens (thicker in the middle and thinner on the edge). If your prescription has a plus power (+2.50) and you require these glasses for distance you are most likely farsighted.
Astigmatism– A normal cornea is perfectly round, however if you have an astigmatism the cornea has an uneven curvature and is oval in shape. Astigmatism is a common visual problem found in over 30% of patients tested. It may accompany farsightness or shortsightedness.
How to correct Astigmatism? By using an astigmatic or toric lens, this lens is specifically designed and is curved to accommodate the cornea shape. If your prescription contains three parts rather than one, you have some form of astigmatism in one or both eyes.
A prescription with three parts could look like this; -2.75/ -1.25 x 90
The first part: This indicates your main power correction. Part Two: This indicates the extent of the astigmatism in dioptres. Part Three: This is the axis describing the direction of the astigmatism.
Presbyopia – This is a vision condition in which the crystalline lens of the eye loses its flexibility, which makes it difficult to focus on close objects. Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-forties. Presbyopia is a natural part of the ageing process of the eye. It is not a disease and it cannot be prevented. This can be corrected with multi-focal lenses, bifocals or with two or more separate pairs of glasses with single vision lenses.
What causes presbyopia? Presbyopia is caused by an age related process. Presbyopia generally is believed to stem from a gradual thickening and loss of flexibility of the natural lens inside your eye.
Symptoms & Signs When people develop presbyopia, they find they need to hold books, magazines and newspapers etc at arms length in order to focus properly.
How to correct Presbyopia? The most common correction for presbyopia is to wear multi-focal (progressive) lenses. Multi-focal lenses offer a more gradual visual transition between the distance and near prescriptions.