The retina, a thin layer of specialized cells at the back of the eye, converts light into electrical signals for the brain, enabling vision. Damage to this tissue, known as retinal damage, can impair this process, leading to vision loss. Understanding its causes is important for eye health.
Health Conditions Affecting the Retina
Systemic health conditions can affect the retina, often leading to progressive vision impairment. Age-related macular degeneration (AMD) is a common cause of vision loss in older adults, impacting the macula, the central part of the retina responsible for sharp, detailed vision. AMD can manifest as “dry” AMD, characterized by macula thinning and drusen deposits, or “wet” AMD, where abnormal blood vessels grow and leak fluid or blood, causing rapid vision loss.
Diabetic retinopathy arises from prolonged high blood sugar levels, which harm the tiny blood vessels supplying the retina. This damage can cause vessels to leak fluid or blood, leading to swelling (macular edema), or to close off entirely, depriving the retina of oxygen. In more advanced stages, new blood vessels may grow on the retina’s surface, which can bleed into the eye or cause the retina to detach.
High blood pressure can also damage retinal blood vessels, leading to hypertensive retinopathy. Elevated pressure can cause the walls of these vessels to thicken and narrow, restricting blood flow to the retina. This can manifest as swelling, hemorrhages (bleeding), or the formation of “cotton-wool spots,” which are areas of nerve fiber damage due to reduced blood supply.
Retinal vein occlusion (RVO) and retinal artery occlusion (RAO) involve blockages in the blood vessels of the retina. RVO occurs when a vein draining blood from the retina becomes blocked, causing blood and fluid to leak into the retinal tissue, leading to swelling and damage. Conversely, RAO involves a blockage in an artery supplying blood to the retina, often due to a blood clot or cholesterol deposit, which deprives retinal cells of oxygen and nutrients, resulting in sudden vision loss.
External Factors and Trauma
Physical impacts or environmental exposures can cause retinal damage. Eye trauma, from blunt force, penetrating objects, or chemical exposure, can harm the retina. Such injuries might cause the retina to tear or detach from its supporting tissue, or lead to bleeding and scarring within the eye. These alterations can disrupt the retina’s function and lead to permanent vision impairment.
Excessive light exposure, particularly to ultraviolet (UV) light from the sun or artificial sources, can induce phototoxicity in retinal cells. This damage, known as photic retinopathy, occurs when light energy triggers chemical reactions that harm photoreceptors and other retinal structures. Prolonged exposure can result in solar maculopathy, where the central retina is damaged, affecting detailed vision.
High myopia, or severe nearsightedness, makes the eye elongated, stretching and thinning the retina. This places mechanical stress on the retinal tissue, making it susceptible to tears or holes. If fluid passes through these openings, it can push the retina away from the back of the eye, causing a retinal detachment. The stretched retina in myopic eyes is also prone to myopic maculopathy, which involves structural changes in the macula.
Inherited and Rare Causes
Inherited predispositions and less frequent issues can contribute to retinal damage. Genetic conditions, such as Retinitis Pigmentosa (RP), involve inherited mutations causing progressive degeneration of retinal photoreceptor cells. This leads to a gradual decline in vision, typically starting with night blindness and peripheral vision loss, eventually narrowing the visual field. RP is a group of disorders caused by gene variants affecting cells’ light response.
Certain medications can have toxic effects on the retina. For instance, some antimalarial drugs like hydroxychloroquine, or tamoxifen used in cancer treatment, can cause retinal toxicity. Regular monitoring by an eye care professional is important for individuals taking these medications to detect early signs of damage.
Infections can inflame and damage the retina. Pathogens such as Toxoplasma gondii (toxoplasmosis) or cytomegalovirus (CMV), particularly in individuals with weakened immune systems, can infect retinal tissue. This can lead to retinitis, an inflammation of the retina that can cause scarring and vision loss.
Autoimmune diseases, where the body’s immune system mistakenly attacks its own healthy tissues, can target the retina. Conditions like systemic lupus erythematosus or Behcet’s disease can cause inflammation within the eye, including the retina and its blood vessels. This inflammation can lead to swelling, cellular damage, and impaired blood flow, resulting in vision problems or loss.