Just as we are advised to watch our blood pressure as we get older, the pressure within our eyes is equally at risk with advancing years.   Changes in the ageing eye can lead to less effective drainage of the clear fluid, known as the aqueous humor, in the eye resulting in a build up of intraocular pressure  (IOP).   A dangerously elevated IOP, or ocular hypertension (OHT) is a major risk factor for glaucoma.

The condition is the third leading cause of blindness in the world.   It can strike at any age, but the elderly are particularly susceptible.   Current estimates of glaucoma are a staggering 100-150 million cases worldwide.   With our ageing population increasing by 5O percent in the US alone over the next years the numbers are expected to soar dramatically.

Notorious for its lack of symptoms, glaucoma can cause progressive damage to the optic nerve without you realizing it.  The damage often involves loss of peripheral vision which is not easily apparent.   It is only when your field of vision has been seriously reduced when patients complain of bumping into things, that the sufferer is likely to head off to a doctor.

As much of the damage to the optic nerve is permanent the conventional management strategy is to prevent any further visual loss by controlling the ocular hypertension and there are no prizes for guessing what doctors turn to as the first line of treatment

Drugs are big business in the glaucoma field.   The way doctors prescribe eyedrops (sometimes combining two or more types) to glaucoma patients has helped to rake in big profits for the ophthalmic drug industry.  

Worldwide sales of medicated eyedrops for glaucoma average $3 billion (USD) each year and account for almost half the total ophthalmic pharmaceutical market.   Given the predicted rise in glaucoma cases in tandem with the ageing population, that sound you can just about hear is the drug companies rubbing their hands in anticipation.  But these seemingly innocuous drops which in most cases have to be taken for life cause a laundry of side effects and are often as dangerous to the body as drugs taken by mouth.

A variety of medicated eyedrops are available for glaucoma and the mechanism by which they lower eye pressure depends on the class of agent they contain.   Needless to say they all come with their own rather extensive menu of side effects.

MIOTICS such as pilocarpine work by constricting the pupil and stimulating the ciliary muscles to increase the drainage of fluid from the eye.  Downside… Because miotics reduce the size of the pupil, a common complaint is blurred or dim vision.  This could also artificially induce night blindness.   Also as these eyedrops need to be administered four times a day patients may find it difficult to keep track regularly.

CARBONIC ANHYDRASE INHIBITORS are available as eyedrops or in an oral form.  These agents inhibit the enzyme involved in producing the aqueous humor thereby decreasing IOP.  Downside…Chronic use of these drops can cause an allergic response with redness and itching of the eye (conjunctiva)as well as scaling on the lower lids.  When taken orally the side effects stretch considerably to include frequent urination, tingling in the fingers/toes, skin rash, gastrointestinal disorders, depression, fatigue, impotence, weight loss and lethargy..

While there are over 20 types of glaucoma, the term is most often used to describe primary open-angle glaucoma (POAG) or chronic glaucoma, the most common form.  In this condition, the aqueous humor – the nutrient fluid produced by the ciliary body (a small gland in the eye) does not drain properly from the eye and into the bloodstream.  Pressure then builds up within the eye resulting in damage to the optic nerve which has the job of transmitting visual messages to the brain.

However although hypertension in the eye’s blood vessels is a key risk factor for glaucoma, not all rises in eye pressure inevitably cause visual damage, in some people, the optic nerve is strong enough to withstand the increased pressure.   Equally those with particularly weak optic nerves can develop glaucoma even if their eye pressure readings are normal.

Who are  most at risk?  Any one can develop glaucoma but the risk is significantly greater for those over 40, and doubles for those who are 74-80.   It is suggested that age-related changes to various parts of the eye may be responsible for the loss of fluid regulation within the eye. Race is another important factor.   In a study funded by the US National Eye Institute, researchers at the John Hopkins University in Maryland found that glaucoma is three to four times more likely in people of Afro-Caribbean origin than in white Europeans, and it strikes at a younger age.  Other high risk groups include family members of those already diagnosed with the condition and people who are extremely short-sighted, diabetic or suffering from high blood pressure.

Glaucoma can also be due to drugs including:
Corticosteroids  - sulpha based drugs – antidepressants – anticoagulants – antihistamines/antacids.
Ironically drugs such as adrenergic and cholinergics which are often used to treat glaucoma can also sometimes bring the condition on.

Beta blockers have been the mainstay of glaucoma treatment for most of the 20 years following their launching in the late 1970s.  They lower eye pressure by reducing aqueous production.  Despite their eroding popularity due to the arrival of the newer prostaglandin analogues these agents are still commonly prescribed.

Beta blocker eyedrops as with all other ophthalmic drops enter the body via tear ducts that connect with the nasal cavity.  This enables the drug to bypass the liver and directly  enter the body’s circulation.   Consequently a significant amount of drug is absorbed- a typical dose (one drop of 0.5 per cent timolol solution in each eye) is as potent as a 10mg oral dose for treating hypertension and angina. 

It is well known that beta-blockers come with an extensive list of side effects some of which may be lethal.   A review of nearly 550 reports of adverse reactions with timolol sent to the National Registry for Drug-Induced Ocular Side Effects found that half  these were linked to systemic reactions affecting the heart, lungs, central nervous system, digestion and skin.

Cardiovascular effects range from arrhythmias (heart-rate disturbances) to full blown congestive heart failure.

ALTERNATIVES TO GLAUCOMA DRUGS.

A large number of glaucoma cases are the result of nutritional deficiencies.   For example it is often due to a weakened antioxidant defense system.   One study of patients with advanced stage glaucoma found significantly reduced amounts of glutathione, an essential component of the cellular antioxidant system in eye fluid.   So filling the following nutritional gaps in your diet could help to prevent or even treat the condition.

VITAMIN A AND OTHER CAROTENOIDS.   In countries where malnutrition is widespread vitamin A deficiency is linked to blindness.   The vitamin is essential for a healthy retina and for strengthening the mucous membranes that surround the eyes.

Beta-carotene a carotenoid that goes to make vitamin A is also a powerful antioxidant.   A Romanian animal study suggests that two other carotenoids, lutein and zeaxanthin, are also important for treating glaucoma and can reduce damage to retinal nerve cells and the optic nerve.

Vitamin C.  In one study high doses of this powerful antioxidant vitamin, given intravenously, dramatically improved patients with open-angle glaucoma.   Those with initially high eye pressures showed the biggest improvements and the effects lasted for up to eight hours.

B Vitamins.  Glaucoma patients are often highly deficient n vitamin B1 (thiamine)  In one study although vitamin B12 did not lower eye pressure, it did halt visual field loss for up to five years

Alpha-lipoic acid (ALA) supplementing with ALA increased glutathione (antioxidant containing the amino-acid cysteine, needed for cell energy and proper immune function) in the red blood cells of glaucoma patients.   In one Russian study of 45 patients with early stage glaucoma, one group was given 150 mg/day of ALA for a month, another was given 75 mg/day for two months and a third group used only medicated eyedrops .  The most improvement in eyesight and in fluid release was seen in the patients taking the highest dose of ALA, despite the shorter treatment time.

Magnesium, zinc and iron.  Deficiencies in these minerals are associated with glaucoma.   In one study 121.5mg of magnesium improved the eyesight of glaucoma patients.

A number of herbal and plant extracts may also benefit glaucoma patients.   These include:-

Ginkgo biloba.  This herb can successfully treat glaucoma and even improve damage to the visual field.   I works by enhancing the general blood circulation,reducing glaucoma-inducing vasospasm (where blood flow is decreased by a sudden contraction of blood vessel walls) and thinning the blood.   Ginkgo also reduces cell toxicity and cell death.
           
Coleus forskohlii.  Forskolin, the active ingredient  in this plant is involved in the production of cyclic adenosine monophosphate which decreases eye fluid flow, thereby decreasing eye pressure.  A number of studies have shown that eyedrops containing forskolin can significantly lower eye pressure for at least five hours.  Indeed in one, it decreased the aqueous flow rate by 34 per cent in healthy human volunteers.

Salvia miltiorrhiza (dan shen).  Often used in traditional Chinese medicine, this plant’s beneficial effects on the micro-circulation of retinal nerve cells and the optic nerve have been demonstrated in animals with ocular hypertension.   Nevertheless, it is important to remember that findings from animal studies do not necessarily apply to humans.