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Glaucoma Physician

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Lifestyle and Nutritional Factors in Glaucoma

Evidence-based exercise and nutrition practices can supplement intraocular pressure lowering.

By: Alexis H. Watson, BSE, Jason S. Flamendorf, MD
Glaucoma Physician June 1, 2023 Vol Ophthalmology Management 27, Issue June 2023 Page(s): 20-22

Related

Intraocular pressure (IOP) is the major modifiable risk factor for slowing glaucoma progression,1 and the leading hypothesis is that elevated IOP results in both mechanical and vascular insults to retinal ganglion cells (RGCs) and their axons.2 However, some individuals experience disease progression despite having IOP in the normal range.3 Independent of IOP, ocular blood flow (OBF) and its ability to maintain adequate perfusion of the optic nerve head and retina, known as autoregulation, likely plays a role in glaucomatous optic neuropathy.4

It is important to consider the role of interventions that are separate from the medical, laser, and surgical therapies that are the mainstays of treatment. A survey of glaucoma patients revealed that 1 in 8 were currently or had used complementary and alternative medicine to treat their disease, and a majority did not disclose this information to their doctors.5 Ophthalmologists need to be prepared to discuss lifestyle and nutritional factors that may influence glaucoma onset and progression, including current evidence pertaining to exercise, nutrition, caffeine consumption, and nicotine use.

Exercise

Exercise can be classified as dynamic or isometric.6,7 Multiple studies have demonstrated that dynamic exercise such as walking, jogging, running, or cycling significantly reduces IOP following exercise, in both healthy participants and glaucoma patients; these reductions can be maintained for up to 30 minutes of rest.8-14 There appears to be a dose-response relationship, with increasing intensity of dynamic exercise associated with greater reductions in IOP.8,10 Both population-based studies and interventional trials have demonstrated that long-term consistent exercise is associated with lower IOP in healthy individuals15,16 and glaucoma patients,13 with a greater benefit from increased frequency or duration of exercise.

Isometric exercises generally produce significant, albeit transient, increases in IOP.17-22 Lifting heavier loads,20,21 performing exercises in the supine position,19 and working larger muscle groups18,22 have been shown to produce greater IOP increases in healthy participants. The rise in IOP seen with isometric exercises has been positively correlated with the rise in blood pressure and retention of CO2, with IOP potentially dropping back to baseline levels at rest due to hyperventilation after exertion.18 Performance of a Valsalva maneuver during these exercises may also explain the IOP increase.23

Despite the rise in IOP, there appear to be no studies that correlate isometric exercises with increased glaucoma incidence or progression. One reason for this may be related to the increased ocular perfusion pressure (OPP), which is calculated as 2/3 of the mean arterial pressure minus the IOP.7 In healthy eyes, the OPP can rise or fall to a certain extent before any increase or decrease in the OBF is observed because of autoregulation. In glaucoma patients, increased OBF following isometric exercise,24,25 and greater vessel density on optical coherence tomography angiography (OCT-A) after dynamic exercise, provide evidence of impaired autoregulation.26 It could be hypothesized that increased OBF would be beneficial to retinal ganglion cells, but the significance of these findings remains uncertain.

Aside from the effects on IOP and OBF, studies have found that exercise has beneficial associations with glaucoma onset and progression. Using NHANES data, Tseng et al found that greater exercise intensity and a less sedentary lifestyle were significantly associated with a decreased likelihood of developing glaucoma.27 Among individuals who have glaucoma or are glaucoma suspects, increased walking and greater time spent doing moderate-to-vigorous physical activity were associated with slower rates of visual field loss,28 as was exercising in the evening.29

There may be certain situations, however, where glaucoma patients should modify their exercise. Individuals with pigmentary glaucoma may be advised to avoid physical activity with jarring movements, such as running, given the potential for significant IOP elevations.30 Studies have demonstrated that wearing swimming goggles can result in increased IOP, decreased OPP, and a narrowing of the iridocorneal angle.31,32 Head-down yoga positions lead to a significant IOP rise in both glaucoma patients and healthy individuals, although it is unclear if there is any association with glaucoma progression.33

Nutrition

The effect of nutrition on onset and progression of glaucoma has been investigated for relationships involving dietary intake of specific foods, macronutrients, and vitamins, with much of the evidence coming from large population-based studies. Foods high in dietary nitrates, such as green leafy, cruciferous, and root vegetables as well as tomatoes, provide an exogenous source of nitric oxide. This is important for aqueous outflow through the conventional pathway and maintenance of OBF autoregulation.34 Kang et al demonstrated that higher dietary nitrate intake was associated with a lower risk of incident glaucoma, in particular decreasing the likelihood of having a paracentral visual field defect upon diagnosis.35

Foods that are rich in antioxidants may also play a beneficial role in reducing glaucoma risk. In a cross-sectional study of African-American women, higher consumption of fruits — especially peaches and oranges — and cruciferous vegetables was associated with a lower likelihood of having glaucoma; individual nutrient intake from food sources found that antioxidant vitamins A, C, and α-carotene were found to be protective.36 Another vitamin that may lower the likelihood of developing glaucoma is B3 (niacin), which is a precursor of the coenzyme nicotinamide adenine dinucleotide (NAD) that is important for energy metabolism. An age-related decline in NAD levels may increase RGC vulnerability to elevated IOP, and a mouse model of glaucoma demonstrated that vitamin B3 supplementation prevents RGC dysfunction and loss.37 In humans, a population-based study showed that higher daily niacin consumption, >21 mg/day, has been linked to approximately 50% decreased odds of developing glaucoma.38

Clinical trials have also assessed the role of niacin supplementation for individuals with glaucoma. De Moraes et al performed a phase 2, randomized, double-masked clinical trial comparing supplementation of nicotinamide and pyruvate with placebo in open-angle glaucoma patients with moderate visual field loss to assess if there are improvements in RGC function as measured by standard automated perimetry.39 With median follow-up of just 2.2 months, there were a higher number of improved test locations and improvement in pattern standard deviation compared to placebo. A separate crossover, double-masked, randomized clinical trial of nicotinamide vs placebo taken for 6 weeks demonstrated an improvement in inner retinal function as measured by electroretinography in the nicotinamide group.40

Another supplement that has garnered attention for its use in glaucoma is ginkgo biloba extract (GBE), which contains multiple flavonoids and is known for improving blood flow and having an antioxidant effect.41 Normal-tension glaucoma (NTG) has been a particular area of interest with respect to GBE because vascular dysregulation is hypothesized to play a greater role in its pathogenesis. A study of NTG patients treated with either GBE or placebo for 4 weeks showed a significantly greater increase in blood flow within the temporal and nasal neuroretinal rim and peripapillary retina of the GBE group.42 Quaranta et al investigated the effect of GBE on visual field damage in individuals with NTG in a randomized, double-masked, crossover trial of GBE vs placebo taken for 4 weeks and found a significant improvement in mean and pattern standard deviation after taking GBE.43 These studies suggest a potential role for nicotinamide supplementation and/or GBE in the treatment of glaucoma patients. However, longer-term studies are required before these interventions can be recommended to patients.

Caffeine

Caffeine is a methylxanthine compound that mediates its physiologic effects primarily through adenosine receptor antagonism. This stimulant is found in a number of commonly consumed sources, including coffee beans, cacao beans, tea leaves, soda, and kola nuts.44 Caffeine has been shown to elevate IOP as soon as 30 minutes after consumption and produce a continued increase through 90 minutes of follow-up in healthy individuals.45 A meta-analysis showed that patients with glaucoma or ocular hypertension had a 2 mmHg mean increase in IOP 90 minutes after consuming caffeine across 8 clinical trials.46 Jiwani et al also found that OPP increased more after drinking caffeinated compared to decaffeinated coffee,47 but there has been conflicting evidence about the net effect on OBF. This could be due in part to the vasoconstrictive effect on the retinal microvasculature, either as a direct effect of caffeine or the result of autoregulation.48,49

Population-based studies have generally found that caffeine consumption does not increase the risk of glaucoma, although higher consumption of caffeinated coffee (5 or more cups in one study, 3 or more in another) has been shown to increase the risk of having primary open-angle glaucoma (POAG) or pseudoexfoliation glaucoma.50,51 In contrast, Wu et al found decreased odds of having glaucoma among those who consumed hot tea,52 although this association could be related to other ingredients in the tea rather than caffeine.

Nicotine

Nicotine can be consumed from several sources including cigarettes, cigars, hookah, pipes, and e-cigarettes. While nicotine use generally has negative health implications, its association with glaucoma is less clear, possibly due to discordant effects on the eye. In a rat model of glaucoma, a nicotine analogue was shown to prevent RGC loss if administered prior to inducing elevated IOP,53 but there are also data that show nicotine may decrease OBF through vasospasm.41 A large US cohort study showed that neither current nor past smokers were at greater risk of developing POAG,54 and Chiam et al found that current smokers actually had lower odds of having NTG within a Chinese Singaporean population.55 In contrast, a study based in China found that patients with POAG were more likely to smoke compared to individuals with primary angle-closure glaucoma or secondary glaucoma.56 E-cigarette use has increased in prevalence, especially among younger smokers, and Golla et al found a significant association between current or former e-cigarette use and greater visual impairment.57 No studies, to date, have reported a relationship between e-cigarettes and glaucoma.

Conclusions

Based on the studies discussed in this review, patients can be given some evidence-based guidance for lifestyle and nutritional factors that may influence their glaucoma. Engaging in consistent exercise, even if low intensity, is beneficial, although specific situations (eg, head-down yoga positions, wearing swim goggles) should be avoided. Eating green leafy and cruciferous vegetables and fruits high in antioxidants may have positive effects on glaucoma as well, but patients are advised to consult their primary care physicians to discuss any potential impact of these dietary changes on medications (eg, warfarin) or other health issues (eg, kidney stones). Taking nicotinamide or GBE shows promise as adjunctive glaucoma treatments, but their benefits and adverse effects need to be studied in longer-term clinical trials. Caffeine consumption is not associated with glaucoma risk, although moderation is recommended, and nicotine use, while having an unclear relationship to glaucoma, is ill-advised for the myriad medical issues it can cause. While IOP remains the major modifiable risk factor for glaucoma, it is important for ophthalmologists to consider lifestyle and nutritional factors that can prevent or slow vision loss from this chronic disease. GP

Alexis H. Watson, BSE, is a graduate of Rutgers University School of Engineering in Piscataway, NJ and is currently an ophthalmic technician at Society Hill Ophthalmic Associates. She has no disclosures.

Jason S. Flamendorf, MD, is an attending physician on the Glaucoma Service of Wills Eye Hospital, and is a glaucoma and cataract surgeon at Society Hill Ophthalmic Associates in Philadelphia, Pennsylvania. He has no disclosures. Reach him at jason.flamendorf@gmail.com.

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