• Acute glaucoma:
Severe throbbing pain in eye with markedly blurred vision
Pupil moderately dilated and fixed
Absence of pupillary light response
Increased intraocular pressure, usually in just one eye
Nausea and vomiting are common
• Chronic glaucoma:
Persistent elevation of intraocular pressure associated with pathological cupping of optic discs
No symptoms in the early stages
Gradual loss of peripheral vision resulting in tunnel vision
Insidious onset in older individuals
• Normotensive glaucoma:
Normal intraocular pressure with no pathological cupping of optic discs
Asymptomatic in the early stages
Gradual loss of peripheral vision resulting in tunnel vision
Insidious onset in older individuals, more common in women than men
Low blood pressure a common underlying feature
Glaucoma most often refers to the vision loss caused by increased intraocular pressure as a result of greater production than outflow of the fluid of the eye (the aqueous humor). The normal intraocular pressure is about 10 to 21 mm Hg. In chronic glaucoma, the intraocular pressure is usually mildly to moderately elevated (22 to 40 mm Hg). In acute glaucoma, the intraocular pressure is greater than 40 mm Hg. Acute glaucoma is a medical emergency; fortunately, it is the rarest form of glaucoma.
Chronic open-angle glaucoma1 is by far the most common form. It accounts for about 70 to 75% of the approximately 3 million cases of glaucoma in the United States.
In some cases glaucoma develops in people with normal intraocular pressure. Referred to as low-tension glaucoma or normotensive glaucoma, this form accounts for approximately 25 to 30% of all glaucoma cases in the United States. Normotensive glaucoma is more common in women than in men and in adults around 60. A common risk factor for normotensive glaucoma is low blood pressure.
Since many patients with glaucoma have no symptoms, it is important that regular eye exams be included in annual checkups for those over the age of 60. Glaucoma is a serious condition that requires strict attention.
Causes
There is a strong correlation between the composition of collagen and chronic glaucoma.2 Collagen is the most abundant protein in the body, including the eye, where it provides strength and integrity to tissues. Inborn errors of collagen metabolism (e.g., osteogenesis imperfecta, Ehlers-Danlos syndrome, and Marfan’s syndrome) are often associated with glaucoma and other eye disease.3 Structural changes in the eye involving the connective tissue network (through which aqueous humor must pass to reach the canal of Schlemm) and blood vessels in the eye have all been observed in glaucoma.2,4–6 These changes may result in elevated intraocular pressure or, perhaps more significantly, lead to the progression of peripheral vision loss. Changes in collagen structure would explain the following:2,4–6
Anatomy of the Eye
• The visual loss in normal-tension glaucoma
• Cupping of the optic disc even at low intraocular pressures
• No apparent anatomical reason for decreased aqueous outflow in chronic or normal-tension glaucoma
Furthermore, since elevated intraocular pressure is not a factor in normal-tension glaucoma, other factors have been suggested that may also have significance in chronic glaucoma:
• Reduced blood flow
• Early nerve cell death
• Nerve irritation
• Excessive glutamate production
• Autoimmune disease
Therapeutic Considerations
Prevention and treatment of chronic glaucoma are dependent on reduction of intraocular pressure and improvement of collagen metabolism. The role of collagen destruction in the etiology of glaucoma is apparent in corticosteroid-induced glaucoma, in which corticosteroids inhibit the manufacture of collagen in the eye.2 Glaucoma patients should not use corticosteroids.
WARNING: Acute closed-angle glaucoma is a medical emergency. Unless it is adequately treated within 12 to 48 hours, a person will become permanently blind within two to five days. Individuals with a narrow anterior chamber angle may spontaneously develop acute glaucoma. The process can be precipitated by anything that dilates the pupil, such as atropine and epinephrine-like drugs. Typical signs and symptoms include extreme pain, blurring of vision, redness, and a fixed and dilated pupil. Agents that dilate the pupils must be strictly avoided in anyone suspected of having glaucoma.
The successful treatment of chronic glaucoma by antiallergy measures has been reported in the literature.7 In one study, many of the 113 patients demonstrated an immediate rise in intraocular pressure of up to 20 mm Hg (in addition to other typical allergic symptoms) when challenged with the appropriate allergen, whether foodborne or environmental. The author speculated that the known allergic responses of altered vascular permeability and vasospasm could result in the congestion and edema characteristic of glaucoma.
Vitamin C
Optimal tissue concentrations of vitamin C are central to achieving collagen integrity. Furthermore, supplemental vitamin C has been demonstrated to lower intraocular pressure in many clinical studies.8–12 For example, in one study a daily dose of 500 mg/kg vitamin C, whether in single or divided doses, reduced intraocular pressure in glaucoma patients by an average of 16 mm Hg.12 Using vitamin C, significant improvements have been achieved in some patients who were unresponsive to common glaucoma drugs.12
The ability of vitamin C to reduce intraocular pressure lasts only as long as supplementation is continued. Although vitamin C therapy is effective orally, intravenous administration results in an even greater reduction.8,10–12 Monitoring of intraocular pressure is required to determine the appropriate individual dose, as some patients respond to as little as 2 g per day, while others will respond only to extremely high doses (35 g per day).8–12 Abdominal discomfort is common with high doses but usually tapers off after three to four days.12 We feel that lower dosages of vitamin C may be possible if supplemental flavonoids are also used to further aid normal collagen metabolism. It is important to understand that the short-term benefits of high doses of vitamin C are primarily due to an osmotic effect, while long-term use of moderate doses is necessary to promote improved collagen strength and integrity of eye tissues.
Flavonoid-Rich Extracts
The most beneficial flavonoids are the anthocyanosides and proanthocyanosides—the blue-red pigments found in many fruits and plant extracts. These compounds elicit a vitamin-C-sparing effect, improve capillary integrity, and stabilize the collagen matrix by preventing free radical damage, inhibiting enzymatic cleavage of collagen, and cross-linking with collagen fibers directly.13–15 Vaccinium myrtillus (European bilberry) extract is particularly rich in anthocyanoside compounds and has been used with good results in improving night vision and diabetic retinopathy. Grape seed and pine bark extract have also shown benefits in several eye disorders. In one study, a combination of bilberry anthocyanoside extract (160 mg) and pine bark extract (80 mg) was studied in 38 asymptomatic subjects with increased intraocular pressure.16 After two months of supplementation with the flavonoids, mean intraocular pressure decreased from a baseline of 25.2 mm Hg to 22.2 mm Hg. After an additional three months of treatment, 19 of the 20 patients taking the flavonoids showed decreased intraocular pressure. No side effects were observed. In addition, the blood flow to eye structures including the retina improved as measured by ultrasound.
Flow of Aqueous Humour
Rutin, a common citrus flavonoid, has also been demonstrated to lower intraocular pressure when used as an adjunct in patients unresponsive to drug therapy alone.17
Ginkgo biloba extract is rich in flavonoids and may be helpful in normotensive glaucoma, based upon the results of two double-blind studies. In the first study, involving healthy human volunteers, ginkgo biloba extract (120 mg per day) significantly increased end diastolic velocity in the ophthalmic artery (23% change), while no change was seen with a placebo. Ginkgo did not alter arterial blood pressure, heart rate, or intraocular pressure.18 In the second study, patients with normotensive glaucoma received either 40 mg ginkgo biloba extract or a placebo three times per day for four weeks, followed by a washout period of eight weeks, then four weeks of the other treatment. After ginkgo treatment, a significant improvement in visual field indicators was recorded, showing that ginkgo improves preexisting visual field damage in some patients with normotensive glaucoma.19
Since calcium-channel-blocking drugs benefit some glaucoma patients, a group of researchers in Switzerland decided to evaluate the effect of supplemental magnesium, which has been referred to as “nature’s physiological calcium-channel blocker.” Ten glaucoma patients (six with chronic glaucoma, four with normotensive glaucoma) participated in the trial. Magnesium was given at a modest dose of 121.5 mg twice a day for one month. After four weeks of treatment, the visual fields improved, and measures of blood flow showed improvement. These results demonstrate that magnesium supplementation improves peripheral circulation and seems to have a beneficial effect on the visual field in patients with glaucoma.20
To evaluate the effect of oral magnesium therapy on blood flow to the eye and visual function, 15 patients with normotensive glaucoma received 300 mg oral magnesium citrate for one month, while 15 patients received no treatment. In the magnesium group, significant improvements were noted in visual field measurements. There was no change in ocular blood flow, so the exact mechanism of magnesium’s effect is not known.21
Chromium
A case-controlled study of 400 eye patients, 52 of whom had chronic glaucoma, found that chronic glaucoma was strongly associated with a deficiency of chromium and low vitamin C intake.22
Fish Oil
In an interesting speculative study, feeding rabbits food soaked with cod liver oil resulted in a 25 mm Hg drop in intraocular pressure, to 11 mm Hg. Intramuscular injections of cod liver oil produced a dose-dependent reduction in intraocular pressure. When the animals were taken off cod liver oil, their intraocular pressure returned to baseline. Control animals given liquid lard or safflower oil experienced no change in intraocular pressure.23 Preliminary studies of the omega-3 fatty acid DHA with human subjects are encouraging.24
QUICK REVIEW
• Acute glaucoma is a medical emergency.
• Prevention and treatment of chronic glaucoma are dependent on reduction of intraocular pressure and improvement of collagen metabolism.
• The most beneficial flavonoids are the anthocyanosides and proanthocyanosides—the blue-red pigments found in many fruits and plant extracts.
• Ginkgo biloba extract may be helpful in normotensive glaucoma.
• Magnesium supplementation improves both chronic and normotensive glaucoma.
• Caffeine intake should be avoided by individuals with glaucoma.
• Exercise is very effective in lowering intraocular pressure.
Many physicians instruct patients with glaucoma to avoid coffee and other caffeinated beverages, and research seems to support this recommendation. Consumption of regular coffee (180 mg caffeine in 200 ml coffee) and decaffeinated coffee (3.6 mg caffeine in 200 ml coffee) was compared in patients with normotensive or chronic glaucoma in a double-blind crossover study.25 Intraocular pressure was monitored in both groups at 30, 60, and 90 minutes after coffee ingestion. In patients with normotensive glaucoma who drank regular coffee, increases in intraocular pressure at 30, 60, and 90 minutes were 0.9, 3.6, and 2.3 mm Hg, respectively; in those who drank decaffeinated coffee, increases were 0.75, 0.70, and 0.4 mm Hg, respectively. The corresponding values in patients with chronic glaucoma were as follows: after regular coffee, increases of 1.1, 3.4, and 3 mm Hg; and after decaffeinated coffee, increases of 0.6, 0.9, and 0.5 mm Hg. This study showed quite clearly that subjects who drank regular coffee demonstrated a greater elevation in intraocular pressure whether they had normotensive or chronic glaucoma.
Exercise can lead to immediate and prolonged reduction in intraocular pressure. Intraocular pressure initially increases within five minutes of starting exercise, then gradually decreases, reaching its lowest level one hour following exercise. The drop in intraocular pressure is approximately 23% in normal individuals, while people with glaucoma usually experience a greater drop and longer duration of postexercise recovery.26 Specifically, the drop in intraocular pressure for glaucoma patients after walking/jogging and running was 7.2% and 12.7%, respectively, more than the decrease experienced by those with normal eyes. Similarly, the mean duration of the pressure drop following running was approximately 84 minutes in those with glaucoma and 63 minutes in those with normal eyes. The lowering of intraocular pressure is independent of systemic blood pressure.
Exercise appears to be effective in lowering intraocular pressure in sedentary subjects engaging in moderate to heavy exercise but is somewhat less effective in physically fit subjects.27 However, it must be pointed out that individuals who are more physically fit tend to have lower intraocular pressure. If one stops exercising, the effect wears off in three weeks. Although exercise may not be effective in lowering intraocular pressure in everyone, it can lead to significant improvements in many. One study found a postexercise intraocular pressure drop of at least 2 mm Hg in 34% of subjects; however, 57% had no change, while 9% had an elevation in pressure.28
TREATMENT SUMMARY
Take general measures to improve overall health. In particular, engage in regular physical exercise and follow the guidelines in the chapter “A Health-Promoting Diet.”
• A high-potency multiple vitamin and mineral formula as described in the chapter “Supplementary Measures”
• Key individual nutrients:
Vitamin C: 500 to 1,000 mg three times per day
Magnesium (bound to aspartate, citrate, fumarate, malate, or succinate): 200 to 300 mg three times per day
Chromium: 200 to 400 mcg per day
Zinc: 30 to 45 mg per day
Vitamin D3: 2,000 to 4,000 IU per day (ideally, measure blood levels and adjust dosage accordingly)
• Fish oils: 1,000 mg EPA + DHA per day
• One of the following:
Grape seed extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Pine bark extract (>95% procyanidolic oligomers): 100 to 300 mg per day
Some other flavonoid-rich extract with a similar flavonoid content, super greens formula, or another plant-based antioxidant that can provide an oxygen radical absorption capacity (ORAC) of 3,000 to 6,000 units or more per day
• For chronic glaucoma:
Vaccinium myrtillus (European bilberry) extract (25% anthocyanidin content): 160 to 240 mg per day
• For normotensive glaucoma:
Ginkgo biloba extract: 240 to 320 mg per day