Macula Sclera Fundus
In ophthalmology, the fundus describes the back interior surface of the eye, opposite the lens, and includes the anatomical structures of the retina, optic disc, macula and fovea.
Cellophane Maculopathysee "Macular Fibrosis"
Best's DiseaseBest’s disease is a disease categorized as a hereditary chorioretinal dystrophy. It is a rare, genetic disease that is characterized by a large, yellow protein that forms under the retinal pigment epithelium (RPE) in the area of the macula.
Inherited eye conditions usually present themselves early in life. Best’s disease is usually diagnosed during childhood, but the onset and severity of symptoms varies. Often, the large, fluid-filled drusen (resembling an egg yolk) beneath the RPE does not affect vision. Eventually, though, this drusen will rupture, and fluid and protein molecules will spread beneath the retina. Central vision will become worse over time, but not to the point of blindness. Best’s disease cannot be cured, but it is possible to adapt quite well to limited vision. Peripheral vision will not be affected, and one eye will often retain good central vision.
Only one copy of the gene responsible for Best’s disease is needed to cause its expression. Therefore, if one parent has the condition, there is a 50/50 chance that a child will inherit the disease. A similar form of Best’s disease that occurs later in life, and whose pattern of inheritance is unknown, is Adult Vitelliform Macular Degeneration.
Adult Vitelliform Macular DystrophyAdult Vitelliform Macular Dystrophy is closely related to Best’s disease. One out of four people with the adult-onset form of this disease has a genetic mutation that causes a fatty, yellow, fluid-filled protein to form beneath the pigment epithelial layer of the retina. In three out of four cases, there is no genetic mutation, and the exact cause for the protein formation is unknown.
In any case, the fluid-filled drusen will eventually rupture, and straight-ahead vision will slowly begin to worsen. Adult vitelliform macular dystrophy cannot be cured, but it is possible to adapt quite well to limited vision. Side (peripheral) vision and night vision will not be affected. This is because the disease affects the macula, and the macula is packed with cones. Rods, the photoreceptors of the retina that enable vision in conditions of low light, are not affected.
IrisIt is the iris that gives the visible eye its color and individuality. The iris consists of pigmented bands of muscle that surround the pupil. It also contracts or expands the pupil in response to light, extreme emotion, and, occasionally, pharmacologic substances
LensThe lens is a dense, transparent structure made of proteins, located just behind the iris and pupil. Its curvature and density cause light waves to bend as they travel through the lens. After passing through the lens, the light waves converge and project an inverted image on the retina. The retina changes the light waves to electric impulses that then travel along the optic nerve to the brain. This entire series of events results in a visual and understandable representation of light and color.
The lens also changes shape in order to focus on objects at various distances. The older one becomes, the stiffer and more inflexible the lens becomes. Oftentimes, the lens becomes so stiff that it cannot change its shape sufficiently to accommodate both images of objects up close and far away. This is why the need for bifocals or reading glasses are common as people age.
New, thin layers continually grow over old layers of the lens. These layers of cells grow inward from the edges but never form in the center of the lens. If the cells at the center of the lens grow cloudy, cataracts develop. Natural lenses can be replaced with artificial lenses in a relatively fast and easy surgical procedure, making cataracts an easily treatable disease.
VitreousThe vitreous is a clear, gel-like substance that fills the area between the lens and the retina. The pressure of the vitreous allows the eye to hold its shape. It also keeps structures like the retina in place.
With age, the composition of the vitreous changes. It may liquefy, allowing small bits of debris to float freely. Sometimes, miniscule collagen fibers clump together within the vitreous. Both create black, spidery flecks called floaters seen in the field of vision. Floaters are generally harmless but will remain within the vitreous unless surgically removed. The changing composition of the vitreous may also cause it to pull on the retina, sometimes resulting in a macular hole or a detached retina.
Rods and ConesThe two types of light-sensitive cells of the retina are rods and cones. Named because of their cylindrical shape, rods are interspersed throughout the retina. They are highly sensitive to low light and shadow and allow for at least some degree of nighttime vision.
Cones are present throughout the retina also, but are very highly concentrated in the fovea of the macula. Different cones are sensitive to different wavelengths and allow one to see vivid colors and sharp detail in conditions of bright light. There are 20 times more rods than cones.
PupilThe opening at the center of the iris through which light enters the eye. The iris causes the pupil to dilate and contract in response to stimuli such as light, extreme emotion, and certain drugs.
The pupil is in direct line with the macula, allowing light to be concentrated where vision is clearest. The iris will contract the pupil in conditions of bright light and will widen the pupil in low light in order to optimize vision.
ChoroidThe choroid is the nourishing layer of the eye located between the retina and the sclera, and is filled with tiny blood vessels. The choroid supplies the outer layer of the retina with blood. In the womb, the choroid gives rise to all other structures of the eye.
MaculaAt the back of the eye, directly in line with the pupil, is an area of the retina called the macula. In the center of the macula is an indentation called the fovea that is packed with cones, cells that require high levels of light in order to function. As light enters the eye through the pupil, it is concentrated into the area of the macula and the fovea. Because of the cones that comprise the macula, central vision is crisp, clear, detailed and in color.
The macula, an area just 5mm in diameter (roughly the thickness of a fingernail), is responsible for the vision that is necessary for many daily activities. Any condition that impairs this area will adversely affect central vision and the ability to carry out many activities that are important to daily life.
ScleraThe white, fibrous, protective outer layer of the eye, composed primarily of collagen and elastic fibers. The sclera varies in thinkness from about 0.3 mm to 1 mm, and is covered by a thin layer of tinnue called the conjunctiva.
AnatomyDiagrams and descriptions of the parts of the eye.
Our eyes allow us to perceive light, dark, and color in astonishing detail, revealing the beauty and complexity of the world around us. Perhaps even more extraordinary is the fact that this organ of vision measures just 24mm (0.95 inches) and weighs 7.5 grams (0.25 ounces)!
The eye's many complex structures, some more obvious than others, are mostly unknown outside of the medical field. In an attempt to eliminate any mysteries, our encyclopedia offers easy to understand definitions of most of the terms you're likely to hear in your ophthalmologist's office, and cross-references them with other relevant terms when appropriate.
AMD- WetIt is common for the macula to break down as one ages. Sometimes, the deterioration of the macula, as well as a predilection to risk factors such as heredity, race (whites are more susceptible than people of darker pigment), smoking, or a high-fat, low-antioxidant diet leads to age-related macular degeneration (AMD).
The wet, exudative form of AMD occurs when the pigment epithelial layer of the macula, located just behind the layer of cells responsible for central vision, sustains such damage that it breaks. Damage to this thin, mesh-like layer of capillaries may occur because of the presence of drusen or because of fluid accumulating in the sub-retinal space between the two layers.
When the pigment epithelial layer breaks, blood leaks into the photoreceptor layer. In most people, new but very fragile capillaries begin to grow back from the broken membrane, and the condition is further classified as neovascular AMD. Instead of forming in an organized fashion, these new blood vessels messily make their way into other layers of the macula like unruly tendrils of a vine. These new vessels often break as well, and along with the broken vascular layer, destroy the healthy macula.
Combined, wet AMD and neovascular AMD account for only 10% of all cases of AMD. Unfortunately, these cases also account for the most severe loss of vision.
For both groups, leakage of blood and other fluids into the macula causes extreme blurriness and even dark “blobs” in the center of vision. Over time, reading and other pastimes requiring detailed, straight-ahead vision will be affected. However, total blindness does not normally occur, since AMD does not affect peripheral vision.
The upside of wet and neovascularized AMD is that there are a number of very effective treatments available, mostly targeting the new blood vessels that form in response to the broken layer between the retina and the choroid. There are currently four anti-vegf agents, Macugen (pegaptanib), Lucentis (ranibizumab), Avastin (bevacizumab), and Eylea (aflibercept) that are used to prevent new, fragile blood vessels from growing back. Additionally, laser photocoagulation and photodynamic therapy work in slightly different ways to seal off broken vessels or destroy new, unhealthy ones.
AMD- DryThe macula deteriorates as one ages. Sometimes, the deterioration of the macula, as well as a predilection to risk factors such as heredity, race (whites are more susceptible to the condition than people of darker pigment), smoking, or a high-fat, low-antioxidant diet leads to age-related macular degeneration (AMD).
The dry form of AMD occurs when yellow deposits called drusen form behind the retina. The larger or more prolific these drusen are, the more damage they cause to the pigment epithelial layer of the macula. This layer is directly behind the photoreceptor layer of the macula and provides the sensory cells with an oxygen- and nutrient-rich blood supply.
Nearly a quarter of people aged 65 to 74 develop age-related macular degeneration. One out of every three people aged 75 or older is afflicted with the disease. Dry AMD is the most common form of AMD.
People with the very early stages of dry AMD rarely experience any noticeable vision problems, but when the pigment epithelial layer sustains damage, central vision loss occurs.
AMD is not painful, though the vision loss it causes can be frustrating. The macula allows one to have crisp, clear central vision. Its break down causes images in the direct line of sight to lose their sharpness. Central vision will become blurred, and over time the ability to perform some activities of daily living and enjoy some common pastimes will be affected. For example, reading and the ability to recognize faces may become difficult. However, total blindness does not normally occur, since AMD does not affect peripheral vision.
There is not a cure for dry AMD, but a specific multi-vitamin and mineral supplement has been found effective in stopping the conversion of the disease from the dry form to the more serious neovascular form of AMD. The supplement, formulated after the release of results from the AREDS 2 study (Age-Related Eye Disease Study), is a combination of anti-oxidants and vitamins that are known to contribute to blood vessel integrity, thus preventing weakened blood vessels from bleeding, breaking, or bursting. The supplement should only be taken under a medical professional’s guidance.
Stargardt's Disease- Fundus Flavimaculatissee “Stargardt’s Disease”