Benefits of exercise preventing eye disease
Macular degeneration is a condition in which the centre of the retina becomes damaged. As the retina is the 'film' of the camera, if it is damaged. It is much more common as we get older, but smoking, genes, and environmental factors contribute.High blood pressure may be related to macular degeneration (below, Ref), This suggests that lowering blood pressure with exercise is likely to be helpful slowing down the development of (below, Ref). Being overweight was observed to be associated with progression of ARMD (below, Ref). We now know for certain that exercise helps, for instance regular exercise reduces risk of wet macular degeneration by 70% .
The macular damage occurs probably due to an increased accumulation of waste products in the retina, although the exact mechanism is unknown (animation here).
Exercise works by reducing insulin resistance, so that the insulin our pancreas naturally releases will have a greater effect on our muscles. Exercise makes the insulin let more glucose into muscle cells, and this lowers the body's blood glucose level.25% of people with diabetes have diabetic retinopathy at any one time. With current treatment, most people with diabetic retinopathy do keep good sight, but many are not so lucky (Ref).
Exercise will help, particularly in the long term. It helps partly by lowering blood pressure (UKPDS, Ref) , and by improving diabetic control in the centre we will notice poor central vision. This will make it difficult to read or see faces or television. (RNIB, diagram).
Glaucoma is a condition in which the optic nerve becomes damaged and vision is reduced. Exercise is likely to help by lowering the pressure on the optic nerve (animation), as indicated below.
Fluid is made in the middle chamber of the eye, and then flows through into the front chamber. It then flows out of the eye through a drainage system. This drainage system is called the 'trabecular meshwork', and the fluid is called 'aqueous fluid' see diagram.
In glaucoma the drain blocks, so fluid gets trapped in the eye. This then makes the pressure in the eye go up. The high pressure in the front of the eye is transmitted back to the optic nerve. The nerve becomes damaged, like a tyre being pumped up too hard, see & see.
The treatment for all types of glaucoma is the same, that is to lower the pressure in the eye (intraocular pressure). The treatment is eye drops, or occasionally surgery or laser (see).
Exercise has been proven to lower intraocular pressure here , here here here. We know that lowering intraocular pressure protects
the optic nerve in glaucoma see and see. We know for certain that exercise lowers blood
we know blood pressure is related to intraocular pressure (Ref);
and we know that a low intraocular pressure helps glaucoma (Ref).
Therefore it is probable that lowering the intraocular pressure with exercise (as well as routine medication) will be helpful, although we will have to wait years for definite proof. Most glaucoma experts recommend regular exercise for patients, as on this page.
In some types of glaucoma the main problem is thought to be poor blood flow to the optic nerve itself. This is 'normal or low tension glaucoma' (see), and again logic would suggest that it is possible for exercise to help by lowering the intraocular pressure.
This is a condition in which the lens of the eye becomes
cloudy or opaque (see). Fortunately surgery is very helpful, but it would
be better still if they could be prevented.
Certain types of cataract are linked to hypertension (below, Ref). As we know exercise lowers blood pressure, it is likely to help a little reducing cataract formation.
Blocked arteries or veins in the retina are serious conditions.
They often cause damage to the retina ('retinal vein or artery occlusion')
Hypertension increases the occurrence of both conditions (below).
Exercise lowers blood pressure, which is a risk factor for these vascular events.
Once again, as exercise keeps blood pressure lower, it is likely to slightly reduce the incidence both conditions (Ref).
High blood pressure often plays a role in other eye conditions or by other mechanisms. Certainly, exercise and having a low blood pressure helps prevent heart attacks, strokes, osteoporosis, arthritis, and cancer (Ref, Ref) (below, Ref),
Lack of exercise may result in a vicious circle of problems. As mentioned, lack of exercise contributes to obesity, which in turn contributes to arthritis ref. In turn the arthritis may prevent further walking Ref, and this may in turn lead to even higher blood pressure.
Exercise and risk taking behaviour
Risk taking behaviour reduced by exerciseparticularly amongst adolescents, e.g. this might include driving without a seatbelt, and risking a serious perforating eye injury; alternatively it may be having sex without a condom, and risking HIV and the retinal infections that may follow (Ref).
Indirect effects of alcohol
Perhaps more importantly risk taking behaviour includes binge drinking, which in turn leads to assaults. 24 years ago in the UK a number of people suffered terrible eye injuries by not wearing a seatbelt. After legislation, this number has reduced dramatically.
But at the same time there has been a dramatic increase in the number of serious eye injuries as a consequence of binge drinking ...yet as above regular exercise reduces binge drinking behaviour (below). Visit any inner-city eye casualty on many Friday and Saturday nights...such injuries occur far too regularly (below, Ref). The eye injury is often suffered by an innocent passer-by.
NHS Direct recommends 30 minutes a day. This is probably enough if you have a reasonably active job, or walk a little during the day. If you drive to work, and park immediately outside your office, then 30 minutes will not be enough. (NHS Direct).
It may be helpful to wear a pedometer to see how much you are walking: certainly some studies show that many of us are not walking enough (Ref).
At present it is difficult to gauge exactly how much exercise contributes, but here are some figures.
- Exercise lowers the eye pressure 1mmHg. A 1mmHg reducion in pressure will cause a 10% reduction in loss of visual field (see)...thus exercise would be expected to result in a 10% reduction in the progression of glaucoma.
- Together with avoiding obesity, exercise will help to prevent at least 50% of type 2 diabetes (2005) (Walking alone may prevent 50% of type 2 diabetes, see). By 2015, when we will all be much heavier, the figure will be greater still.
- Exercise has similar effects on the cardiovascular system...exercise such as walking reduced the risk nearly 50% .
We know that diseases such as macular degeneration are caused in part by the same
factors that cause heart disease, so it is likely exercise may help
to reduce these a little.
One of the ways exercise may help is by improving our blood fat levels. It lowers triglycerides, which are harmful, and increases HDL, which prevent disease.
- Exercise makes us less likely to participate in risk taking behaviour, which can damage our own health, or influence our behaviour so others may be affected by our actions.
Although exact figures are unknown, lack of exercise contributes significantly to several eye conditions affecting the elderly, with a slightly lower contribution for middle age patients.