- Macula and fovea are two parts of the retina that work together to aid in vision. The macula, which is densely packed with cone cells, is the dark reddish patch at the center of the retina that provides the central, or straight-ahead, vision which allows for seeing fine detail in reading or other close-up work. The fovea is a small depression within the macula, and contains only cone cells that provides the sharpest vision. Outside the macula, the retina contains mainly rod cells, which cannot process images as sharply as the cone cells within the macula but are, however, responsible for peripheral and night vision. The foveal sight is quite sharp and enjoys two other advantages, besides having the most concentration of cones. The fovea has very little overlying retinal layers or blood vessels to obstruct light rays, and its cones have a more direct wiring circuit to the brain.
Macular edema is a condition of the macula stemming from retinal edema. The macula is an indentation of the retina that contains an abundance of cones (light-sensitive cells responsible for discerning color and detail). Light is focused directly on the macula by the eye, making it the center of sharpest sight. Retinal edema occurs when the capillaries of the retina bleed, filling the spaces between retinal cells with fluid. Retinal edema may be present throughout the retina and involve the macula, or it may be contained in a general area that spares the macula. If the macula is spared, vision may be relatively unaffected at first. However, the macula tends to accumulate the fluid. In this case, macula edema occurs. The condition is characterized by inflammation of the macula and blurred or impaired vision. If untreated, macular fluid collects in small pockets of space and forms cysts, a condition called cystic macular edema. The condition leads to degeneration of the macula, by which central vision may be permanently lost. Macular edema is the result of diabetic retinopathy, hypertension, retinal vein obstruction, traction of the vitreous, such inflammations as liveitis and retinitis, and cataract surgery. It is diagnosed with fluorescein angiography, a procedure in which fluorescein dye is injected into a vein in the arm and monitored as it passes through the veins of the retina. Macular edema may right itself spontaneously or persist. Treatment varies according to the cause. Cases as a result of inflammation are treated with corticosteroids. Those conditions of edema caused by vascular problems and diabetes may be treated with photocoagulation, a treatment that uses a laser to seal leaking blood vessels. There is no treatment for edema resulting from traction or cataract surgery.
Mercury toxicity can be seen in the eyes. According to Dr. Hal Huggins (a dentist who has done much to bring awareness of mercury toxicity in amalgams and one who has virtually been ignored because of it), mercury streaks can be seen on the retina through an ophthalmoscope. Dr. Doty Murphy had been noting that black streaks were often seen in people who had amalgams but were absent in those without them and alerted Dr. Huggins to this finding. The medical profession considers these to be areas where the elongated near-sighted eye has put tension on the retina and stretched it so that the epithelium shows through. However, when amalgams were removed, the black areas began to disappear. Dentists also see these black spots and call them “amalgam tattoos”, which are thought to occur when a sloppy dentist will accidentally cut a gum and some of the amalgam becomes lodged in the area causing a “tattoo” of sorts. Interestingly, dentists were finding them elsewhere – the roof of the mouth, down the bony ridge an inch away from a lower tooth, and even on the uvula (the little finger-like projection that hangs down at the back of the throat). Not even the sloppiest dentist could manage that. Ophthalmologists began to take note – but only some. More are learning that myopia and cataracts are related to mercury in fish and amalgams and that more research needs to be done in this area. There are many eye solutions and treatments that do contain mercury, so it is wise to ask your dentist not to prescribe or recommend those.
Mowat sensor is a mobility aid designed for use by visually impaired persons and developed by Humanware. The device uses high-frequency sound waves to detect objects in the user’s path. The sensor vibrates if an object is present and increases the vibration rate as the user nears the object. The sensor has a short range for objects less than one meter away and a longer range for objects up to four meters away. Approximately the size of a flashlight, the device may be hand held or carried in a pocket or purse. A model for those with poor tactual sensation produces an audible signal heard through an earphone attachment. Other similar devices are manufactured under various names, including the Bliss passive detector. The device is designed to be used with a long cane or dog guide. Several hours of practice and/or training with a qualified instructor are required for proficient use.