r vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from theInside the eye, just behind the pupil is a lens. Like a lens inside a camera. This natural lens of the eye has the shape of a tiny discus. In youth this lens is very pliable and there is a muscle within the eye which makes the lens change shape. As the lens changes shape the focus of the eye is adjusted. This is why young children can see clearly in the distance but can also read within inches or their nose. This ability to adjust the focus of the eye from distance to near vision is called “accommodation”.

Unfortunately as we get older the lens becomes stiffer little by little. This is very predicable and unavoidable. Gradually the focus adjustment power of the eye declines. The nearest point that can be seen clearly moves further away. If the eye is neither long or short sighted, reading at a normal distance usually becomes difficult from mid forties onwards; especially if one attempts to read small print, in poor light, when tired. From then on reading spectacles are needed.

This will happen at an earlier age if the eye is “long sighted”. This is because in this condition the eye is optically under powered for distance vision. To overcome this some of the focusing reserve of the eye must be used just to maintain clear distance vision. There is then less focusing reserve for near vision.

The process (called “loss of accommodation”) continues so that by mid 60’s the lens is so stiff that it cannot change shape at all. The eye has become fixed focus. This loss of the ability to focus and see clearly for near vision is called “presbyopia”.

Science has not yet come up with a way of truly restoring the natural focus adjustment ability to the aged eye. Solving this problem is at the frontier of current research.

Nevertheless there are several ways in which this middle age loss of near vision can be helped, and dependence on reading spectacles reduced. If both eyes have good vision then the focus of one can be set for distance whilst the other is set for near vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from the

ation”.

Unfortunately as we get older the lens becomes stiffer little by little. This is very predicable and unavoidable. Gradually the focus adjustment power of the eye declines. The nearest point that can be seen clearly moves further away. If the eye is neither long or short sighted, reading at a normal distance usually becomes difficult from mid forties onwards; especially if one attempts to read small print, in poor light, when tired. From then on reading spectacles are needed.

This will happen at an earlier age if the eye is “long sighted”. This is because in this condition the eye is optically under powered for distance vision. To overcome this some of the focusing reserve of the eye must be used just to maintain clear distance vision. There is then less focusing reserve for near vision.

The process (called “loss of accommodation”) continues so that by mid 60’s the lens is so stiff that it cannot change shape at all. The eye has become fixed focus. This loss of the ability to focus and see clearly for near vision is called “presbyopia”.

Science has not yet come up with a way of truly restoring the natural focus adjustment ability to the aged eye. Solving this problem is at the frontier of current research.

Nevertheless there are several ways in which this middle age loss of near vision can be helped, and dependence on reading spectacles reduced. If both eyes have good vision then the focus of one can be set for distance whilst the other is set for near vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from the

will happen at an earlier age if the eye is “long sighted”. This is because in this condition the eye is optically under powered for distance vision. To overcome this some of the focusing reserve of the eye must be used just to maintain clear distance vision. There is then less focusing reserve for near vision.

The process (called “loss of accommodation”) continues so that by mid 60’s the lens is so stiff that it cannot change shape at all. The eye has become fixed focus. This loss of the ability to focus and see clearly for near vision is called “presbyopia”.

Science has not yet come up with a way of truly restoring the natural focus adjustment ability to the aged eye. Solving this problem is at the frontier of current research.

Nevertheless there are several ways in which this middle age loss of near vision can be helped, and dependence on reading spectacles reduced. If both eyes have good vision then the focus of one can be set for distance whilst the other is set for near vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from the

lity to focus and see clearly for near vision is called “presbyopia”.

Science has not yet come up with a way of truly restoring the natural focus adjustment ability to the aged eye. Solving this problem is at the frontier of current research.

Nevertheless there are several ways in which this middle age loss of near vision can be helped, and dependence on reading spectacles reduced. If both eyes have good vision then the focus of one can be set for distance whilst the other is set for near vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from the

r vision. This concept is called “monovision” or “blended vision”. It is a compromise. A deliberate difference is created between the eyes. Some people adapt to this and others never do. To work well it requires the brain to ignore, or be unaware of, the eye that is out of focus. As gaze changes from distance to near (and vice versa) the brain should switch from attending with one eye to the other so that whatever is being looked at is seen in focus with the appropriate eye; whilst the blur from the fellow eye is not noticed. The standard of near vision is rarely as good as with spectacles, as with specs’ both eyes are in focus together, whereas with monovision only one eye is providing focused near vision. Some patients are bothered by the compromised distance vision in the near sighted eye, e.g. when driving at night.

Monovision can be achieved with contact lenses and various forms of eye surgery; e.g. laser refractive surgery (LASIK, LASEK, Epi-LASIK), Conductive Keratoplasty (CK), or through Refractive Lens Exchange. Which form of surgery is most appropriate will depend on the initial focus state of the eyes. If both eyes have perfect distance vision (little or no refractive error) then CK to the non dominant eye may be best. However if there is a large initial error in both eyes, too great to fix with laser surgery, then Refractive Lens Exchange is perhaps a better option.

Refractive Lens Exchange involves surgery very similar to a cataract operation. The natural lens is removed from the eye and replaced with an artificial lens; called the “lens implant”. The power of the lens implant is chosen to give the eye the focus required.

In an attempt to provide a single eye with both distance and near vision a multifocal implant may be used. However these do reduce the quality of vision somewhat. Lens implants that provide some focus adjustment for near vision do exist but this is far short of that naturally present in the youthful eye.