Blurred vision in the context of "Pernicious anemia"

Myopia, also known as near-sightedness and short-sightedness, is an eye condition where light from distant objects focuses in front of, instead of on, the retina. As a result, distant objects appear blurry, while close objects appear normal. Other symptoms may include headaches and eye strain. Severe myopia is associated with an increased risk of macular degeneration, retinal detachment, cataracts, and glaucoma.

Myopia results from the length of the eyeball growing too long or less commonly the lens being too strong. It is a type of refractive error. Diagnosis is by the use of cycloplegics during eye examination.

Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin or the cells of the body becoming unresponsive to insulin's effects. Classic symptoms include the three Ps: polydipsia (excessive thirst), polyuria (excessive urination), polyphagia (excessive hunger), weight loss, and blurred vision. If left untreated, the disease can lead to various health complications, including disorders of the cardiovascular system, eye, kidney, and nerves. Diabetes accounts for approximately 4.2 million deaths every year, with an estimated 1.5 million caused by either untreated or poorly treated diabetes.

The major types of diabetes are type 1 and type 2. The most common treatment for type 1 is insulin replacement therapy (insulin injections), while anti-diabetic medications (such as metformin and semaglutide or tirzepatide) and lifestyle modifications can be used to manage type 2. Gestational diabetes, a form that sometimes arises during pregnancy, normally resolves shortly after delivery. Type 1 diabetes is an autoimmune condition where the body's immune system attacks the beta cells (β-cell) in the pancreas, preventing the production of insulin. This condition is typically present from birth or develops early in life. Type 2 diabetes occurs when the body becomes resistant to insulin, meaning the cells do not respond effectively to it, and thus, glucose remains in the bloodstream instead of being absorbed by the cells. Additionally, diabetes can also result from other specific causes, such as genetic conditions (monogenic diabetes syndromes like neonatal diabetes and maturity-onset diabetes of the young), diseases affecting the pancreas (such as pancreatitis), or the use of certain medications and chemicals (such as glucocorticoids, other specific drugs and after organ transplantation).

Refractive error is a problem with focusing light accurately on the retina due to the shape of the eye and/or cornea. The most common types of refractive error are near-sightedness, far-sightedness, astigmatism, and presbyopia. Near-sightedness results in far away objects being blurry, far-sightedness and presbyopia result in close objects being blurry, and astigmatism causes objects to appear stretched out or blurry. Other symptoms may include double vision, headaches, and eye strain.

Near-sightedness is due to the length of the eyeball being too long; far-sightedness the eyeball too short; astigmatism the cornea being the wrong shape, while presbyopia results from aging of the lens of the eye such that it cannot change shape sufficiently. Some refractive errors occur more often among those whose parents are affected. Diagnosis is by eye examination.

Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of sight" because the loss of vision usually occurs slowly over a long period of time. A major risk factor for glaucoma is increased pressure within the eye, known as intraocular pressure (IOP). It is associated with old age, a family history of glaucoma, and certain medical conditions or the use of some medications. The word glaucoma comes from the Ancient Greek word γλαυκός (glaukós), meaning 'gleaming, blue-green, gray'.

Of the different types of glaucoma, the most common are called open-angle glaucoma and closed-angle glaucoma. Inside the eye, a liquid called aqueous humor helps to maintain shape and provides nutrients. The aqueous humor normally drains through the trabecular meshwork. In open-angle glaucoma, the drainage is impeded, causing the liquid to accumulate and the pressure inside the eye to increase. This elevated pressure can damage the optic nerve. In closed-angle glaucoma, the drainage of the eye becomes suddenly blocked, leading to a rapid increase in intraocular pressure. This may lead to intense eye pain, blurred vision, and nausea. Closed-angle glaucoma is an emergency requiring immediate attention.

Astigmatism is a type of refractive error due to rotational asymmetry in the eye's refractive power. The lens and cornea of an eye without astigmatism are nearly spherical, with only a single radius of curvature, and any refractive errors present can be corrected with simple glasses. In an eye with astigmatism, either the lens or the cornea is slightly egg-shaped, with higher curvature in one direction than the other. This gives distorted or blurred vision at any distance and requires corrective lenses that apply different optical powers at different rotational angles. Astigmatism can lead to symptoms that include eyestrain, headaches, and trouble driving at night. Astigmatism often is present at birth, but can change or develop later in life. If it occurs in early life and is left untreated, it may result in amblyopia.

The cause of astigmatism is unclear, although it is believed to be partly related to genetic factors. The underlying mechanism involves an irregular curvature of the cornea and protective reaction changes in the lens of the eye, called lens astigmatism, that has the same mechanism as spasm of accommodation. Diagnosis is by an eye examination called autorefractor keratometry (objective, allows to see lens and cornea components of astigmatism) and subjective refraction.

Macular degeneration, also known as age-related macular degeneration (AMD or ARMD), is a medical condition which may result in blurred or no vision in the center of the visual field. Early on there are often no symptoms. Some people experience a gradual worsening of vision that may affect one or both eyes. While it does not result in complete blindness, loss of central vision can make it hard to recognize faces, drive, read, or perform other activities of daily life. Visual hallucinations may also occur.

Macular degeneration typically occurs in older people, and is caused by damage to the macula of the retina. Genetic factors and smoking may play a role. The condition is diagnosed through a complete eye exam. Severity is divided into early, intermediate, and late types. The late type is additionally divided into "dry" and "wet" forms, with the dry form making up 90% of cases.

Eye strain, also medically termed as asthenopia (from astheno- 'loss of strength' and -opia 'relating to the eyes'), is a common eye condition characterized by non-specific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache, and occasional double vision.

These symptoms tend to arise after long-term use of computers, staring at phone screens, digital devices, reading, or other activities that involve extended visual tasks. Various causes contribute to eye strain, including uncorrected vision problems, digital device usage, environmental factors, and underlying health conditions. When concentrating on a visually intense task, such as continuously focusing on a book or computer monitor, the ciliary muscles and the extra-ocular muscles are strained, also contributing to the symptoms. These symptoms are broadly classified into external (related to the ocular surface) and internal symptom factors (related to eye muscles).

A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief period of memory loss, brief loss of consciousness, problems with balance, nausea, blurred vision, and mood changes. Concussion should be suspected if a person indirectly or directly hits their head and experiences any of the symptoms of concussion. Signs and symptoms of a concussion usually occur within minutes to hours of the injury, usually within 72 hours. However, symptoms may be delayed by 1–2 days after the accident. It is not unusual for symptoms to last 2 weeks in adults and 4 weeks in children. Symptoms of a concussion may make it difficult to return to work, school, sports (in cases of sports related concussions) or prior level of functioning, with disability usually lasting days to weeks. Fewer than 10% of sports-related concussions among children are associated with loss of consciousness.

Common causes include motor vehicle collisions, falls, sports injuries, and bicycle accidents. Risk factors include physical violence, drinking alcohol and a prior history of concussion. The mechanism of injury involves either a direct blow to the head or forces elsewhere on the body that are transmitted to the head. This is believed to result in neuron dysfunction, as there are increased glucose requirements, but not enough blood supply. A thorough evaluation by a qualified medical provider working in their scope of practice (such as a physician or nurse practitioner) is required to rule out life-threatening head injuries, injuries to the cervical spine, and neurological conditions and to use information obtained from the medical evaluation to diagnose a concussion. Glasgow coma scale score 13 to 15, loss of consciousness for less than 30 minutes, and memory loss for less than 24 hours may be used to rule out moderate or severe traumatic brain injuries. Diagnostic imaging such as a CT scan or an MRI may be required to rule out severe head injuries. Routine imaging is not required to diagnose concussion and is, by definition, normal after concussions.

Vitamin B₁₂ deficiency, also known as cobalamin deficiency, is the medical condition in which the blood and tissue have a lower than normal level of vitamin B₁₂. Symptoms can vary from none to severe. Mild deficiency may have few or absent symptoms. In moderate deficiency, feeling tired, headaches, soreness of the tongue, mouth ulcers, breathlessness, feeling faint, rapid heartbeat, low blood pressure, pallor, hair loss, decreased ability to think and severe joint pain and the beginning of neurological symptoms, including abnormal sensations such as pins and needles, numbness and tinnitus may occur. Severe deficiency may include symptoms of reduced heart function as well as more severe neurological symptoms, including changes in reflexes, poor muscle function, memory problems, blurred vision, irritability, ataxia, decreased smell and taste, decreased level of consciousness, depression, anxiety, guilt and psychosis. If left untreated, some of these changes can become permanent. Temporary infertility, reversible with treatment, may occur. A late finding type of anemia known as megaloblastic anemia is often but not always present. In exclusively breastfed infants of vegan mothers, undetected and untreated deficiency can lead to poor growth, poor development, and difficulties with movement.

Causes are usually related to conditions that give rise to malabsorption of vitamin B₁₂ particularly autoimmune gastritis in pernicious anemia. Other conditions giving rise to malabsorption include surgical removal of the stomach, chronic inflammation of the pancreas, intestinal parasites, certain medications such as long-term use of proton pump inhibitors, H2-receptor blockers, and metformin, and some genetic disorders.

The blue light spectrum, characterized by wavelengths between 400 and 500 nanometers, has a broad impact on human health, influencing numerous physiological processes in the human body. Although blue light is essential for regulating circadian rhythms, improving alertness, and supporting cognitive function, its widespread presence has raised worries about its possible effects on general well-being.

Prolonged exposure to blue light poses hazards to the well-being of the eye and may cause symptoms like dry eyes, weariness, and blurred vision. As our dependence on digital devices and artificial lighting increases, it is crucial to understand the complex pathways of the blue light spectrum that affect biological processes. To reduce the hazards of blue light exposure, effective management strategies can be implemented, including limiting screen time before bed and using blue light filter.

Postural orthostatic tachycardia syndrome (POTS) is a condition characterized by an abnormally large increase in heart rate upon sitting up or standing. POTS in adults is characterized by a heart rate increase of 30 beats per minute within ten minutes of standing up, accompanied by other symptoms. This increased heart rate should occur in the absence of orthostatic hypotension (>20 mm Hg drop in systolic blood pressure) to be considered POTS. POTS is a disorder of the autonomic nervous system that can lead to a variety of symptoms, including lightheadedness, brain fog, blurred vision, weakness, fatigue, headaches, heart palpitations, exercise intolerance, nausea, difficulty concentrating, tremulousness (shaking), syncope (fainting), coldness, pain or numbness in the extremities, chest pain, and shortness of breath. Many symptoms are worsened with postural changes, especially standing up. POTS symptoms may be treated with lifestyle changes such as increasing fluid, electrolyte, and salt intake, wearing compression stockings, slowing down postural changes, exercise, medication, and physical therapy.

POTS is mainly caused by problems in the autonomic nervous system, which controls heart rate and blood flow. This may include blood pooling in the legs instead of returning to the heart, or the heart beating faster to make up for low blood pressure. In other cases, it develops after a viral infection, surgery, trauma, autoimmune disease, or pregnancy. It has also been shown to emerge in previously healthy patients after contracting COVID-19, in people with Long COVID (post-COVID-19 condition), or possibly in rare cases after COVID-19 vaccination, though causative evidence is limited and further study is needed. POTS is more common among people who got infected with SARS-CoV-2 than among those who got vaccinated against COVID-19. About 30% of severely infected patients with long COVID have POTS. Risk factors include a family history of the condition.