It is only 10 AM, but you feel like the day is dragging on. You may feel cranky, tense, or restless. You might notice that you are rubbing your eyes, blinking more than usual, and struggling to soothe the burning sensation in your eyes. This may be your body's way of reacting to different stressors. Stress is a subjective experience that affects people in diverse ways. In this blog post, we will briefly discuss the mechanism of stress and its impact on your daily activities, especially those that involve the visual system.
According to the World Health Organization (WHO), “Stress can be defined as a state of worry or mental tension caused by a difficult situation. Stress is a natural human response that prompts us to address challenges and threats. Everyone experiences stress to some degree. The way we respond to stress, however, makes a big difference to our overall well-being.”
Stress Response
When faced with stress, whether actual or perceived, the body triggers a response known as the "fight or flight" response which involves either fighting or escaping from the threat. This fight or flight response, also known as the stress response, is automatically triggered by the nervous system. After the nervous system perceives stressors, it activates the hypothalamus-pituitary-adrenal (HPA) axis, the sympathetic nervous system, and the immune system. The sympathetic nervous system prompts the endocrine system to release hormones that help us cope with the stressor. The endocrine system then produces and releases hormones such as cortisol and adrenaline into the bloodstream, which sets off a chain of physiological responses in our body. These physiological responses include muscular contraction, increased heart rate to boost blood flow, rapid breathing to increase oxygen supply and remove carbon dioxide waste, systematic redistribution of blood to specific areas of the body, and an increase in glucose supply.
To improve visibility and focus on the perceived threat, the ciliary muscles in the eyes contract, and the pupils dilate. Once the stressor has passed, the parasympathetic nervous system restores the body to its normal state of balance (homeostasis). However, extended exposure to high levels of stressors or intense stress can lead to an overproduction of stress hormones that can disrupt the stress response system and cause imbalances in the body. Prolonged exposure to stressors or intense stress is known as chronic stress, and it can negatively impact your overall health.
When experiencing chronic stress, stress hormones can lead to several physical reactions. These include continuous muscle contractions and tension, changes in breathing patterns, a constant increase in blood flow that can cause high blood pressure, and a steady blood supply to larger muscles needed for quick movement while reducing blood flow to areas not necessary for fight or flight.
Chronic Stress and the Eye
Tunnel vision is peripheral vision loss due to constriction of the visual field. Individuals with tunnel vision can only see objects placed directly in front of them. Depending on the causal factor, tunnel vision may be temporary or permanent. Stress-related tunnel vision is usually temporary due to the contraction of the ciliary muscles in response to stressors. Other causes of tunnel vision include glaucoma, retinitis pigmentosa, stroke, and migraines.
Ocular migraines cause visual disturbances such as zig-zag lines, flashes of light, and tunnel vision. These migraines are triggered by a variety of factors such as hormonal changes, restricted ocular blood flow, light sensitivity, eye strain, fatigue, dehydration, anxiety, and insomnia. Ocular migraines are generally harmless and are characterized by small blind spots that may cause temporary vision loss. However, if it persists or worsens, it may indicate more serious underlying health issues. Interestingly, some individuals may develop migraines after experiencing stress and then relaxing.
Floaters are not caused by chronic stress, but they appear more noticeable due to the increased sensitivity caused by it. They may be caused by various factors and can take different shapes. The eye contains two kinds of fluids- vitreous humor and aqueous humor, which help maintain its shape and nourish the tissues. The vitreous humor, a gel of collagen fibers, fills the back of the eye between the lens and the retina. In certain conditions such as aging, trauma, or disease, the vitreous gel may liquefy or shrink, resulting in the formation of opaque debris that floats in the vitreous. These floating fragments are known as floaters and can appear as dots, cobwebs, flies, or lines. It can be very worrisome when first noticed and may also affect vision if directly positioned on the visual axis. Floaters move with eye movement and are more visible when looking at a plain or bright background. Over time, people may adapt to the existence of floaters and no longer see them, but this does not necessarily mean they have disappeared. While floaters are usually harmless, they may be indicative of more serious eye issues.
Twitching or Spasms of the Eyelids is a slight involuntary movement of the eyelids. It can be caused by muscular tension in the eyelid muscles, fatigue, light sensitivity, and eye strain.
Light sensitivity and blurry vision occur due to the continuous contraction of the muscles that dilate the pupils. When the pupils dilate, they become larger to allow more light into the eyes, thus transmitting more visual information about the immediate environment to the brain. However, in prolonged exposure to stress, the eyes become sensitive to light causing glare and blurry vision.
Glaucoma is one of the leading causes of vision loss and blindness in the United States. It usually occurs when elevated eye pressure damages the nerve that connects the eye to the brain (optic nerve). Glaucoma may progress more rapidly in individuals with chronic stress. Stress is a risk factor for glaucoma, as studies have shown that psychological stress can induce IOP even in healthy individuals. Decreased ocular blood flow and emotional distress (anxiety, depression, etc.) can contribute to increased intraocular pressure (IOP).
Central serous retinopathy (CSR) results from an accumulation of fluid (from the choroid) under the central part of the retina- macula. Stress and steroid medications are the two main risk factors for developing CSR. It is commonly observed in men between the ages of 30 to 50. Studies have shown that high cortisol levels and maladaptive stress responses can cause inflammation and leakages. Though CSR typically affects one eye at a time, it can occur in both eyes at the same time. CSR causes no pain. It may manifest as sudden visual disturbances, lead to the detachment of the retinal pigment epithelium layer, or even vision loss. CSR can resolve without treatment within 4-6 months, as vision may be restored once the fluid drains. Visit your eye care provider, as it may worsen and cause permanent vision loss if left untreated. Studies also show that CSR can predict transient ischemic attack (“mini-stroke”). CSR can be clinically detected and monitored with optical coherence tomography (OCT), a rapid, non-invasive retinal imaging technology.
Dry eye disease (DED)
is a common chronic condition of the ocular surface that occurs when the eyes cannot stay adequately lubricated. The tear film consists of three layers (the outer fatty layer, the middle watery layer, and the inner mucus layer) that maintain eye health by providing lubrication and protection. An imbalance in the tear film or deficiency in tear production can result in dry eyes. DED may manifest as grittiness, itching, burning sensation, redness, discomfort, and blurry vision. Stress does not cause dry eyes, but it can make it worse. If left untreated, it may cause severe damage.
Sources
1. World Health Organization. Stress.
https://www.who.int/news-room/questions-and-answers/item/stress#:~:text=Stress%20can%20be%20defined%20as,experiences%20stress%20to%20some%20degree
2. Shin, Da Young, et al. "The effect of anxiety and depression on progression of glaucoma." Scientific Reports 11.1 (2021): 1-10
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4. Sesar, Anita Pusic et al. “Personality Traits, Stress, and Emotional Intelligence Associated with Central Serous Chorioretinopathy.” Medical science monitor: international medical journal of experimental and clinical research vol. 27 e928677. 10 Jan. 2021, doi:10.12659/MSM.928677
5. Tsai, Der-Chong et al. “Central serous chorioretinopathy and risk of ischaemic stroke: a population-based cohort study.” The British journal of ophthalmology vol. 96,12 (2012): 1484-8. doi:10.1136/bjophthalmol-2012-301810
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7. Chu B, Marwaha K, Sanvictores T, et al. [Updated 2022 Sep 12]. “Physiology, Stress Reaction.” In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK541120/