The retina is the light-responsive tissue that lines the back of the eye. Rays of light focus onto the retina through the cornea, pupil, and lens. The retina transfigures the light rays into impulses that move through the optic nerve to the brain, where they are comprehended as the images we see. Simply put, the retina transports images through the optic nerve to the brain and consists of millions of cells that detect light like a camera. A healthy retina is necessary for clear vision.
Diseases and conditions of the retina include:
- Age-Related Macular Degeneration
- Diabetic Retinopathy
- Retinal Detachment
- Macular Hole/Pucker
- River Blindness/Onchocerciasis
- Retinitis Pigmentosa
Age-related macular degeneration is the most prevalent cause of blindness and central vision loss in adults over the age of 65, and unfortunately does not typically become apparent until a person starts to experience vision loss. Yellowish deposits called drusen develop under the retina as part of the normal aging process, and as they grow in number and size, they can inhibit proper functioning of the retina by killing the light sensitive cells of the macula (central area of the eye). This can cause blurring of central vision and a detrimental effect on the ability to enjoy everyday activities like reading, driving, and even recognizing the faces of friends and family members.
Diabetic retinopathy is a complication of diabetes and one of the most common vision impairment problems in the United States and throughout the world in general. Diabetic retinopathy leads to damage of the retinal blood vessels and occurs in over half of patients diagnosed with diabetes. The longer a person lives with diabetes, the more the chance for developing diabetic retinopathy increases. Diabetic retinopathy leads to vision loss by one of two ways:
- Diabetic macular edema—swelling or thickening of the macula (central part of the retina) that leads to diminished vision.
- Proliferate diabetic retinopathy—poor circulation to the retina, causing development of growth factors and resulting in new blood vessels and scar tissue on the surface of the retina. New blood vessels may bleed into the center of the eye causing vision loss and possibly even retinal detachment. Sometimes, new blood vessels and scar tissue even cause fluid to become trapped in the eye, which increases intraocular eye pressure and creates a rare form of glaucoma (neovascular glaucoma). Vision may be even further damaged and the person may experience significant eye pain.
A detached retina is the separation of the tissue lining the back of the eye from its supporting layers of blood vessels, which supply the retina with nourishment and oxygen. Usually retinal detachment is an emergency situation and occurs when there is a reduction or contraction of the vitreous fluid (gel-like material) that occupies the inside of the eye. This can cause a pulling on the retina and a retinal tear that results in retinal detachment. If a person experiences “floaters” (objects seeming to flat across the eye) or sees a grey veil advancing across their field of vision, these could be signs of retinal detachment.
The macula is the central region of the retina, and a macular hole is a small full thickness retinal defect in this area. Macular pucker is also known as epiretinal membrane and denotes the building of semitransparent scar tissue on the surface of the retina. Over time, this causes contraction and disfiguration within the retina’s underlying layer and/or macular edema (swelling). People with macular holes my experience blurred or distorted central vision, difficulty reading and driving, and even loss of vision.
Retinoblastoma is a rare eye cancer of the retina that is most typically seen in young children and infants. Symptoms of retinoblastoma include poor vision, a lazy eye, an abnormal white reflection from the retina (leukocoria), and in rare cases, inflammation of the eye. Retinoblastoma develops from a gene mutation occurring during cell division. If gene mutation runs in the family, a child’s chances of developing retinoblastoma significantly increases, but in at lease half of thesecases, there is no family history of eye cancer. Usually children diagnosed with retinoblastoma are 5 years old or younger, and retinoblastoma can develop in babies as young as 1 year old.
River blindness (onchocerciasis) is a parasitic condition that affects people in many countries around the world. River blindness is the primary cause of blindness in 30 different African nations, as well as in Yemen and six Latin American countries. River blindess is passed on to humans through the blackfly, which lives along the riverbanks. When a person is infected, the parasite moves to all internal tissue of the eye, excluding the lens, resulting in bleeding, eye inflammation, and other problems leading to blindness. The parasite can cause both systematic symptoms in the body and symptoms in the eye as well. Systematic symptoms include itching (localized and then spreading to whole body), rash, skin pigmentary (color) changes, skin nodules, and an enlarged groin. Eye symptoms include cataracts, itching, intraocular inflammation, and sensitivity to light.
Retinitis pigmentosa is a genetically inherited retinal condition that essentially affects the rods (photoreceptors) of the eye, which are the light-sensing cells accountable for night and peripheral (side) vision. Retinitis pigmentosa can distinctively be identified through pigmentary (color) changes seen during a dilated eye examination. The disease can be inherited through an autosomal (non sex-related) dominant chromosome, an autosomal recessive chromosome, or an X-linked (female-linked) chromosome (inheritance often only seen in males because passed through unaffected mothers). Symptoms of retinitis pigmentosa can appear as early as childhood, but side effects may not become noticeable until adulthood. Symptoms include cataracts, loss of central vision, night blindness, and loss of peripheral (side) vision. Simply, retinitis pigmentosa is caused by defects in particular genes that cause damage to the retina. In some cases, the disease gradually progresses and may be discovered during a routine eye examination.