Climate Change and its Impact on Eye Care

Dr. Abhishek Mandal, Ph.D.

Senior Business Adviser, Vision Science Academy, London, U.K.

Climate change is a global phenomenon which refers to a gradual increase in the overall temperature of our environment accompanied by measurable changes in weather patterns; events which usually arise secondary to human intervention (e.g., air pollution) (Wheeler & Watts, 2018).

Climate change has had a lasting impact over human health throughout the world, and that includes eye care as well. Human health can be negatively influenced by climate change in the following ways:

1. Direct adverse effects of environmental disasters such as heavy snowfalls, heat waves, famines, and floods.
2. Changing weather patterns and changes in the distribution of disease-carrying vectors in the environment.
3. Indirect effects due to inefficiently managed human health programs, thereby leading to malnutrition.

Visual Disorders and Climate Change

The earth’s upper atmosphere has suffered from a steady decline in its ozone concentrations which is mainly attributed to an abundance of chlorofluorocarbons (CFCs). This has created several ozone holes which have led to a persistent surge in the amount of ultraviolet (UV) radiations reaching the earth’s surface, a key factor in global warming. Most of the adverse effects of climate change on human vision can be attributed to these dangerously high levels of UV radiation.

Following are a few examples of visual health conditions showing how our vision can deteriorate secondary to climatic changes:

Cataract

Cataract usually arises due to lenticular degeneration secondary to aging-related changes, but climate change has also been found to precipitate it. Recently, there has been a significant rise in the number of cataract cases throughout the globe, which is mainly attributed to the increased levels of ozone, and oxides of nitrogen and sulfur within our environment (Shin, Lee, & Kim, 2020). Furthermore, at least 20% of cataract cases are believed to be a direct result of a gradually rising exposure to ultraviolet (UV) radiation which can lead to overproduction of reactive oxygen species (ROS) within the ocular lens (Zhang, Yan, Löfgren, Tian, & Lou, 2012).

Macular Degeneration

The retinal macula is highly sensitive to climate changes, and cohort studies have revealed that long-term exposure to intoxicants (oxides of nitrogen and carbon) can lead to a greater risk of age-related degeneration of macula or AMD (Chang et al., 2019). Overexposure to UV radiations is another potential risk factor often linked to AMD, although the evidence is still insufficient (Jaggernath, Haslam, & Naidoo, 2013).

Ocular Infections

Changing temperatures in our environment can undoubtedly provoke the proliferation of disease-carrying vectors. This can lead to a reemergence of infectious morbidities (e.g., ocular trachoma and several tick-borne infections) within developed countries (Jaggernath et al., 2013).

Keratoconjunctivitis

Global warming and the resultant dry weather have drastically increased the incidence of dry eyes, which also increases the overall risk of corneal and conjunctival infections. Chronic exposure to pollutants such as nitrogen oxide and particulate matter also predisposes to keratoconjunctival pathologies (Miyazaki et al., 2019).

Additionally, increasing accumulation of UV radiations within our atmosphere is also a contributing risk factor to recurrent herpes zoster ophthalmicus, especially among immunosuppressed patients (Zak-Prelich, Borkowski, Alexander, & Norval, 2002).

Retinal Detachment

Exposure to an excessive amount of ambient heat has been correlated to an elevated risk of retinal detachment which is as high as 2.5 times below the age of 75 years (Auger, Rhéaume, Bilodeau-Bertrand, Tang, & Kosatsky, 2017).

Ocular Tumors

An excessive UV exposure can also lead to an increased risk of developing uveal melanoma, one of the commonest ocular tumors (Jaggernath et al., 2013). Moreover, it is related to a potentially higher risk of developing carcinomas such as basal cell carcinoma of the eyelids.

(Source: Ivanov, I. V., Mappes, T., Schaupp, P., Lappe, C., & Wahl, S. (2018). Ultraviolet radiation oxidative stress affects eye health. Journal of biophotonics, 11(7), e201700377)

COP26 Conference: Tackling the issue of Global Warming

The COP26, an international climate change conference, was recently held in October-November, 2021 at Glasgow, Scotland (Mountford et al.). The conference, which was attended by representatives belonging to 190+ countries, was aimed at keeping the global temperature rise to a bare minimum of 1.5°C. Any higher temperatures can potentially disrupt the quality of all life forms on our planet. Human vision too, can seldom bear the long-term outcome of an uncontrolled global warming.

Following were the salient points of discussion at COP26:

1. Mitigation: Reducing carbon emissions and utilization of eco-friendly fuels.
2. Adaptation: Assisting the nations who are adversely impacted by climate change.
3. Finance: Providing financial aid to countries to help mitigate global warming.
4. Collaboration: Combined efforts to curb climate change.

Role of Vision Science Professionals

Since UV radiations and most of the other hazardous environmental changes are preventable, patients suffering from eye conditions need to be offered proper counselling regarding climate change at every visit as well as its negative impact on their vision.

Patients should be advised to wear hats so they can prevent the UV radiation from reaching their eyes. Use of protective glasses can be adopted to prevent eye from both dryness and UV radiations. However, neither hats nor glasses can protect us from the radiations that strike our eyes more peripherally. For this purpose, ordinary sunglasses can be replaced by ski goggles or wrap-around sunglasses. Additionally, UV-absorbing contact lens offer yet another reliable source of protection. Moreover, patients should be counselled regarding their hydration status as it is a very important factor for protection against ocular dryness and corneal infections (Cullen, 2011).

On a separate note, vision science professionals must collaborate with environmentalists to spread public awareness on this growing issue. Moreover, it is equally imperative to gather data pertaining to the overall impact of climate change on ocular health, and then set measurable goals to achieve desirable results in the line of visual health. The COP26 conference should serve as a perfect role model for this purpose.

References

1. Auger, N., Rhéaume, M. A., Bilodeau-Bertrand, M., Tang, T., & Kosatsky, T. (2017). Climate and the eye: Case-crossover analysis of retinal detachment after exposure to ambient heat. Environ Res, 157, 103-109. doi:10.1016/j.envres.2017.05.017
2. Chang, K. H., Hsu, P. Y., Lin, C. J., Lin, C. L., Juo, S. H., & Liang, C. L. (2019). Traffic-related air pollutants increase the risk for age-related macular degeneration. J Investig Med, 67(7), 1076-1081. doi:10.1136/jim-2019-001007
3. Cullen, A. P. (2011). Ozone depletion and solar ultraviolet radiation: ocular effects, a United nations environment programme perspective. Eye Contact Lens, 37(4), 185-190. doi:10.1097/ICL.0b013e318223392e
4. Jaggernath, J., Haslam, D., & Naidoo, K. S. (2013). Climate change: Impact of increased ultraviolet radiation and water changes on eye health. Health, Vol.05No.05, 10. doi:10.4236/health.2013.55122
5. Miyazaki, D., Fukagawa, K., Fukushima, A., Fujishima, H., Uchio, E., Ebihara, N., . . . Inoue, Y. (2019). Air pollution significantly associated with severe ocular allergic inflammatory diseases. Sci Rep, 9(1), 18205. doi:10.1038/s41598-019-54841-4
6. Mountford, H., Waskow, D., Gonzalez, L., Gajjar, C., Cogswell, N., Holt, M., . . . Gerholdt, R. COP26: Key Outcomes From the UN Climate Talks in Glasgow.
7. Shin, J., Lee, H., & Kim, H. (2020). Association between Exposure to Ambient Air Pollution and Age-Related Cataract: A Nationwide Population-Based Retrospective Cohort Study. Int J Environ Res Public Health, 17(24). doi:10.3390/ijerph17249231
8. Wheeler, N., & Watts, N. (2018). Climate Change: From Science to Practice. Curr Environ Health Rep, 5(1), 170-178. doi:10.1007/s40572-018-0187-y
9. Zak-Prelich, M., Borkowski, J. L., Alexander, F., & Norval, M. (2002). The role of solar ultraviolet irradiation in zoster. Epidemiol Infect, 129(3), 593-597. doi:10.1017/s0950268802007793
10. Zhang, J., Yan, H., Löfgren, S., Tian, X., & Lou, M. F. (2012). Ultraviolet radiation-induced cataract in mice: the effect of age and the potential biochemical mechanism. Invest Ophthalmol Vis Sci, 53(11), 7276-7285. doi:10.1167/iovs.12-10482