We all wonder what effect diet, exercise, sun exposure and other behaviors have on our general health and, since this is an eye site, our eyes. The proposition that we can take action to affect our health is an appealing idea to some and totally ignored by others. For those that are interested there are things you can do to affect your long term eye health.

One of the most significant articles to be published in 2007 was a review of literature regarding lifestyle exposures and eye disease, by Barbara and Ronald Klein. These authors, from the University of Wisconsin, have a decades long history as leading investigators in the epidemiology of eye disease making their comments particularly authoritative. (Amer J of Ophthalmol. 2007;144:961-969.)

Following are highlights from their review.

1. Cataract

Smoking. For every 10-pack-years of smoking the risk of cataract (nuclear type) increases 9%. (A pack-year amounts to smoking one pack per day for one year.) Smoking cessation reduces risk.

Diet and Supplements. Multiple large national studies have been done in the US, UK, Europe and Australia. Findings varied from study to study, and the recent AREDS group found no effect of their antioxidant formulation on cataract development. So if there is a protective effect it is mild. “Available data at this time are not sufficient to support a recommendation for taking high concentrations of vitamins, minerals, supplements, or a combination thereof to prevent cataract.” (p.963)

Light Exposure. It seems relatively clear that exposure to light, specifically Ultraviolet B, increases risk of cataract (cortical type). In the Beaver Dam, Wisconsin, group wearing glasses for refractive correction from an early age reduced nuclear cataract by 22% and cortical cataract by 33%. Wearing a hat and sunglasses reduced cataract slightly. Even so, a hat and UV protective lenses are recommended as prudent protective measures for people who spend a significant amount of time in the sun.

Note, UV protective coating is nearly clear. Dark glasses and polarization are helpful for comfort, but it is the UV coating that is protective.

2. Age-Related Macular Degeneration

Smoking. Increases risk of progression to late stage AMD; risk of 33% increase in atrophic form, and 25% increase in neovascular form. The risk is further increased in people with genes for Complement Factor H and LOC387715.

Diet and Supplements. AREDS is the one large randomized trial that found a positive effect of supplementing antioxidant vitamins and zinc. See Vitamins and Macular Degeneration for the details. Another 4 year, 1, 200 person study did not show any effect for Vitamin E alone.

The use of Lutein, Zeaxanthin and Omega-3 fatty acids have shown beneficial effects in epidemiologic studies. All three are being included in AREDS 2.

Light Exposure. Although there are theoretic reasons to expect macular damage from light, especially blue and UV, any effect on the retina must be small as it has not been detected in multiple large national studies.

Physical Activity. In one large study in Beaver Dam, Wisconsin, people who were significantly active at least 3 times a week were 70% less likely to develop neovascular complications. The authors point out this population had the same incidence of AMD and the same rate of geographic atrophy whether they exercised or not.

3. Diabetic Retinopathy

Smoking. Though multiple studies did not confirm the expected worsening of retinopathy with smoking, the authors recommend cessation of smoking because overall mortality is 1.5 times greater in diabetics who smoke.

Diet and Supplements. After controlling for blood sugar and blood pressure there are several studies showing that dietary supplements do not affect the course of diabetic retinopathy.

Physical Activity. Because exercise has such a good effect on diabetes in general it is unexpected that there is little epidemiologic data studying exercise and retinopathy.

4. Glaucoma.

There is no data suggesting smoking or dietary factors affect open angle glaucoma.

Small studies suggest exercise might help reduce pressure.

If you want to read the article in full it is in the American Journal of Ophthalmology, December 2007, pages 961 to 969. In the article each category has a discussion of the pertinent study or studies with a full set of references.

So, exercise is good for many things. Smoking is bad. UV protection is recommended. Dietary supplement with antioxidants probably helps slow macular degeneration.

Macular Degeneration (AMD) is one of the biggest unsolved problems in ophthalmology. In the later decades in life there is gradual deterioration of the central part of the retina resulting in reduced central vision for reading and seeing details.

Retinal Photo of moderate Macular Degeneration (AMD).

The yellow spots, called “drusen,” are the accumulation of waste products in the pigmented layer under the retina. There is no leakage, so this is the “dry” type.

There are two general categories of AMD:

• The “Dry” type: There are drusen and or atrophy, but there is no leakage of serum or blood. Vision worsens progressively, but slowly.
• The “Wet” type. Starts as dry, but at some point new blood vessels invade the space under the retina. The new vessels leak serum or blood which causes a relatively rapid and severe loss of central vision.

Historically, there was nothing we could do about dry type, except maintain a vigil for development of leakage. If leakage developed, and was caught early, a laser could be used to cauterize the leaking vessels. More recently this is being treated with an injected medication.

In 1988 a small study was published (Newsome, Arch Ophthal 1988; 106: 192-198) suggesting dietary supplement with the mineral zinc could slow progress of macular degeneration. That led to a much larger nationwide study looking at age-related eye diseases, particularly cataract and macular degeneration, to see if supplementation with antioxidant vitamins and or zinc would be of help.

AREDS

AREDS, the Age Related Eye Disease Study, followed almost 5,000 people for ten years. They were divided into the following treatment groups:

• Antioxidant Vitamins (daily dose):

Beta Carotene 15 mg; Vitamin C 500 mg; Vitamin E 400 IU

• Minerals: Zinc 80 mg; Copper 2 mg
• Antioxidant Vitamins and Zinc
• Placebo

After AREDS started two contemporary studies looking at vitamins and lung cancer found that smokers who took Beta-Carotene had increased risk of lung tumors and mortality. Smokers in the study were allowed to drop out or change to a supplement without Beta-Carotene.

Copper was included because Zinc and Copper compete for absorption so if you supplement one you must balance with the other.

The above vitamin dosages are available by taking 2 tablets of Preservision (Bausch & Lomb) or 4 tablets of ICaps (Alcon).

The Study

There are several things you need to know to understand the study result.

At the outset each participant’s retina was graded according to the severity of the AMD. The grading was on a scale of 1 to 4, from mild to advanced, represented on the chart below by the different colors.

The Dry Type, given enough time, can progress to wasting or “atrophy” of the central retina with severe vision loss.

The Results

Arch Ophthal 2005;123:1570-1574.

The above graph summarizes the study results over 10 years of followup.

The X-axis is years. The Y-axis is the percentage of people that developed advanced vision loss, either from the dry type advanced to atrophy or from the wet type.

Within each group half received placebo, and half the supplement. The dashed line represents those receiving a placebo. The solid line represents those receiving both antioxidant vitamins plus zinc.

It is fairly clear that within each group taking the vitamins lessened the chance of developing severe vision loss. It did not reverse degeneration or eliminate vision loss, but it did provide a measurable benefit.

Can lowering eye pressure help prevent the development of glaucoma?

Ocular Hypertension is the term we use when the eye pressure is above the normal range, but has not caused any damage. When damage occurs due to pressure then we use the term glaucoma.

Ocular Hypertension Treatment Study

In 1994 recruitment began for a large nationwide study of people who had elevated intraocular pressures to answer that very big question.

Criteria for enrollment in the study was pressure of 24 or above in at least one eye, and no evidence of glaucoma damage at baseline. (Average pressure is 16, with the normal range extending up to 20.)

1,636 people were enrolled and followed for a minimum of five years.
Participants were divided into two groups:

• Half were assigned to receive pressure lowering drops
• Half were observed without treatment.

Overall Result

Arch Ophthalmol. 2002;120:701-713

POAG is Primary Open Angle Glaucoma.

This chart, scanned from one of the OHTS articles, shows the comparison of rates of developing glaucoma between the untreated group and the group that got pressure lowering drops. It clearly shows that lowering pressure reduces the chance of developing glaucoma. Note it does not reduce it to zero.

Pressure Level and Glaucoma Risk

Arch Ophthalmol. 2002;120:714-720

This table is enlarged from the size in the original article, but it contains such useful information that it is worth a bigger look. The X-axis is corneal thickness. The Y-axis is pressure. The height of the bars represents percent chance of developing glaucoma.
Clearly, if you have thinner corneas and higher pressures you have an increased chance of developing glaucoma.

Optic Nerve and Glaucoma Risk

Arch Ophthalmol. 2002;120:714-720

This table accompanies the above table 1. This time the Y-axis is the vertical cup-to-disc ratio, which is a measure of the thickness of the rim of the optic nerve. A higher VCD means a thinner rim of nerve tissue
Clearly people who have thinner rims, higher VCD, have an increased risk of developing glaucoma.

Estimating Risk

During an eye exam we perform the following tests:

• measure pressure, on everyone
• measure corneal thickness (if pressure or nerve is suspect)
• examine the nerve to estimate VCD, on everyone
• visual fields (if other finding suspicious)

So, at your exam, we can get a pretty good starting estimate of glaucoma risk. If nerve and field show no damage then we can refer to the above charts and discuss your risk of developing glaucoma and whether or not you want to start pressure-lowering drops. For the person who consistently takes their medication and follows-up with regular monitoring it is rare to lose vision to glaucoma.

In studying glaucoma one frequent question that arises is whether there is a time of day when the intraocular pressure (IOP) is expected to be the highest? It is reasonable to ask if pressure follows a circadian rhythm like other functions in the body, and if pressure is predictable then we would know the best time of day to check pressure. Sounds logical, but consider the following studies.

Pressure at different times of day.

A German group led by Jost Jonas made the following measurements. In 547 Caucasian patients who had glaucoma or were glaucoma suspects the pressures were measured at 7 am, 12 noon, 5 pm, 9 pm and 12 midnight. A record was made for each patient noting the high and low readings. The following table shows the percentage of people that had their maximum pressure at a given time of day.

Time of Day

Percent of Participants with Highest IOP at that Time

In this study pressure peaks are rather evenly spread throughout the day, with a possible preponderance at midnight. Jonas concluded that taking pressure from 7 am to 9 pm had a greater than 75% chance of missing the highest pressure reading of the day.

[AJO. 2005;139:1136]

Diurnal, by the way, means during the day, as opposed to nocturnal. That difference comes into play in the following report from Japan.

Pressure during Sleep

Takahashi Hara and his group measured pressures in 148 glaucoma patients in the sitting position and lying down. Pressure was measured every two hours from 6 am to midnight and at 3 am. (Results below are given as mean ± SD. Pressure units are mmHg.)

Result #1:

• The average pressure peak while sitting was 16.0 ± 2.7.
• The average pressure peak lying down was 18.9 ± 3.9.

At all time points the pressure was higher lying down.

Why should that be? Sitting up the heart is about 12 inches below the eyeball. Venous return is downhill. Lying down the eye and heart are at the same level so increased venous pressure causes more resistance to outflow from the eye.

Result #2:

• The pressures measured lying down ended up being the highest pressures of the 24 hour period.

Why are pressures lying down a significant question? Because we spend 8 hours a day lying down sleeping, those are the hours when the pressure is highest.

Note, the diurnal pressure peaks were evenly spread through the day as in the Jonas study.

[Arch Ophthal. 2006;124:165-168]

Possible Effect on Treatment Choice

Do the above results affect treatment decisions regarding glaucoma? Consider the following. The production of aqueous humor is highest during the day and decreases, about 45%, during sleep. Drops like Timolol work by decreasing aqueous production. Therefore, that class is most effective during the day, but less so at night. That is why, for those taking the once-a-day form of Timolol, we recommend taking it in the morning.

Another class of glaucoma medications, Prostaglandins (Xalatan, Travatan, Lumigan), seems to be equally effective at all time periods.

However, Trusopt and Azopt supposedly work on the same part of the eye as Timolol, but they had pressure lowering equal to the Prostaglandins during sleep.

[Invest Ophthal and Vis Sci. 2006;47:2917-2923]

Various aspects of pressure fluctuation have been under study for a long time with different studies giving different results. Whether or not coming in for pressure checks at midnight, 3 am and 6 am will make a difference in treatment is not yet clear. And there are new longer lasting treatments that will be arriving soon that may render that question moot. However you answer the above questions, the principal remains that if there is glaucoma damage, then whatever pressure you have is too high and it is worth the effort to get it lower.

CB June 2008