Oxygen toxicity
The supplementation of oxygen can lead to oxygen toxicity, also known as oxygen toxicity syndrome, oxygen intoxication, and oxygen poisoning. There are two main types of oxygen toxicity: central nervous system (CNS) toxicity, and pulmonary and ocular toxicity.Temporary exposure to high partial pressures of oxygen at greater than atmospheric pressure can lead to central nervous system toxicity (CNS). An early but serious sign of CNS oxygen toxicity is a grand-mal seizure, also known as a generalized tonic-clonic seizure. This type of seizure consists of a loss of consciousness and violent muscle contractions. Signs and symptoms of oxygen toxicity are usually prevalent, but there are no standard warning signs that a seizure is about to ensue. The convulsion caused by oxygen toxicity does not lead to hypoxia, a side effect common to most seizures, because the body has an excess amount of oxygen when the convulsion begins. The seizures can lead to drowning, however, if the convulsion is suffered by a diver still in the water.Prolonged exposure to higher oxygen levels at atmospheric pressure can lead to pulmonary and ocular toxicity. Symptoms of oxygen toxicity may include disorientation, respiratory problems, myopia, or accelerated development of cataracts. Prolonged exposure to higher than normal partial pressures of oxygen can result in oxidative damage to cell membranes. Signs of pulmonary (lung) oxygen toxicity begin with slight irritation in the trachea. A mild cough usually ensues, followed by greater irritation and a worse cough until breathing becomes quite painful and the cough becomes uncontrollable.
Pathophysiology
The changes in hypertensive retinopathy result from damage and adaptive changes in the arterial and arteriolar circulation in response to the high blood pressure. Diagnosis
Fundoscopy and patients history. Differential Diagnoses
Several other diseases can result in retinopathy that can be confused with hypertensive retinopathy. These include diabetic retinopathy, retinopathy due to autoimmune disease, anemia, radiation retinopathy, and central retinal vein occlusion. Keith Wagener Barker (KWB) Grades
Grade 1
Vascular Attenuation
Grade 2
As grade 1 + Irregularly located, tight constrictions – Known as "AV nicking" or "AV nipping" – Saluss sign
Grade 3
As grade 2 + Retinal edema, cotton wool spots and flame-hemorrhages "Copper Wiring" + Bonnets Sign + Gunns Sign
Grade 4
As grade 3 + optic disc edema + macular star "Silver Wiring"There is an association between the grade of retinopathy and mortality. In a classic study in 1939 Keith and colleagues described the prognosis of people with differing severity of retinopathy. They showed 70% of those with grade 1 retinopathy were alive after 3 years whereas only 6% of those with grade 4 survived. The most widely used modern classification system bears their name. The role of retinopathy grading in risk stratification is debated, but it has been proposed that  individuals with signs of hypertensive retinopathy signs, especially retinal hemorrhages, microaneurysms and cotton-wool spots, should be assessed carefully. Management
A major aim of treatment is to prevent, limit, or reverse target organ damage by lowering the persons high blood pressure to reduce the risk of cardiovascular disease and death.