The time that this becomes a problem varies considerably. The eyes, like many other parts of the human body, age on different schedules for different people. At what age one would notice the effects of presbyopia depends upon not only the physiologic agin g of the eye, but also on the demands placed on the vision system. Someone who rarely reads is less likely to notice a problem than someone often involved in near vision tasks. Using your eyes does not make the situation worse, and in fact may delay the o nset of acute symptoms. This is one example of the "use it or loose it" principal.
Details regarding the many types of spectacle bifocals are in the Abstract: Spectacle Lenses and for detailed bifocal contact lens information, see the EyeCare Report: Contact Lenses
Step 1: "tromboning": Start by holding an object with relatively small reading print, such as business card, at arm's distance away from your eyes. Make sure that the object is located in the mid-line centered with your nose and not favoring e ither eye. It should also be located slightly below eye level. Begin by focusing on the card and slowly bring it closer to your eyes. A rate of movement about one inch (2.5cm) per second is correct. At a certain point the image will begin to blur. Stop he re and concentrate and try to clear the image for two seconds. Now reverse the process and push the card away from your eyes. When you reach the limit of your arm's length, look at distance object at least 20 feet (6m) away. Immediately return your at tention and focus to the near card and repeat the process of bringing it closer to your eyes. Repeat this process ten times.
Step 2: "Straddling the blur point push ups": Bring the near object in to the point of just noticeable blur. While concentrating to keep it focus, very slowly bring it closer to the point of increased blur. Now really strongly make an effort to cl ear the image. You may notice that your peripheral vision appears to dim slightly. This is because the extraordinary effort you are putting forth to focus is also causing your iris pupil to constrict, thereby reducing the total amount of light entering yo ur eye. This is good feedback indicating you are making maximum effort to focus! Now push the near object back away to the point of clear vision and then bring it closer in to the point of blur and again, really concentrate to clear the blur. Repeat ten t imes. Now repeat step 1, tromboning for ten more time.
That's it! You should do this exercises two or three times per day. Results are often apparent within a few days and maximum benefit is achieved within about a month.
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We can measure these changes microscopically usually by the forth or fifth decade of life. As our lenses age, less light is passed through and there is a gradual loss of brightness in our visual world. There is also a slight skewing of color perception a s the blues and greens become less vivid, especially relative to reds and yellows. Most people not involved in extremely demanding visual tasks would not notice these changes until the lens material is significantly altered. The point at which we notice these changes is when we refer to the lens as having cataracts.
We have come to understand that there are nutritional, dietary and environmental factors which may contribute to the severity and onset of these changes. It appears that exposure to ionizing radiation, ultraviolet light, systemic diseases such as diabetes and certain medications including oral corticosteroids like prednisone may play a role in the aging of our eyes. Trauma to the eye, such as might result from of a head injury or an object striking the eyeball can cause cataracts.
Cataract surgery is one of the most common and successful medical procedures in the world today. The tired, old and yellowed crystalline lens is removed and replaced by a new clear plastic model. Vision is restored to "like new" (assuming there a re no other problems inside your eye) and often the new lens optics can be designed to eliminate or reduce the need for eyeglasses. The new lens, called an implant, is fixed focus, either for distance or near. Some people choose to set the focus for dista nce and use glasses for near and some choose a near lens and use eyeglasses for distance! Some people even choose to have one eye set for far and the other for near, called monovision, which eliminates the need for eyeglasses altogether. Researchers are working on a number of lens implant designs which focus, much like the original equipment! These special implants are currently available in some countries and may be a routine product in a few years.
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The macula is a specific area of the retina rich with the photoreceptors responsible for fine, sharp, clear central vision. The remainder of the retina allows for peripheral (off to the sides) vision and motion perception. If the fovea centralis, the very center of the macula, is damaged, a blind spot occurs directly in the center of your vision. The areas just outside this area might be perfectly fine! In ARMD, the macula becomes damaged and central vision deteriorates. This is not correctable with spec tacle lenses, although magnifiers can sometimes enlarge the image so that undamaged photoreceptors can process the information.
One common optical test for ARMD is called the Amsler Grid. This is a white-on-black background grid pattern which, when viewed at distance of 12" (30cm), can reveal missing or distorted areas in the central visual field. Microscopically, the optomet rist or ophthalmologist examines the macula to observe defects in the structure of the area.
Science is now just beginning to understand the mechanisms that cause ARMD. Again, as in other aging-related changes, there appears to be a nutritional component. Nicotine and possibly alcohol are drugs which seem to play a role, as do certain medications . Some systemic diseases may also effect macular function. Curiously, there are some diseases that can effect the rest of the retina but do not effect the macula! Experimental surgical procedures using a type of laser focused on the retinal tissues and un derlying blood vessels may be appropriate for certain types of macular degenerations but may be completely ineffective for others. There are ophthalmologists who specialize in retina laser surgery who should be consulted for this disorder. One clear fact is that the sooner it is diagnosed, the more likely a treatment plan may work to save the vision. This is yet another reason for people in their sixties and older to have regular, yearly examination by an optometrist or ophthalmologist.
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In recent months, researchers have found that a number of common nutrients are involved in the aging of the eye. These antioxidants and key elements active in the metabolic processes include: the vitamins ascorbic acid (vita C) the tocopherols (vita E) an d the carotinoids (beta-carotene, xyline, lutein) The minerals zinc, chromium and selenium as well as the amino acid l-glutathione are also involved in the process. Does taking more of these nutrients into your body slow the aging process? There are ma ny causes responsible for the aging of the eye (and the rest of us!) and micronutrients certainly play a role. Quite a few health practitioners and nutritionists now recommend supplementation of these vitamins, minerals and amino acids.
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Retina detachment occurs for many reasons, including secondary to PVD as described above. The retina is actually a multi-layered tissue consisting of a neurological layer, a vascular layer (the blood supply) and a pigmented layer. In RD, one or more of th ese layer separate. The neurological layer, deprived of its blood supply, begins to die and areas of blind spots develop. Some people are predisposed to detachment resulting from anomalies in the structure of the eye. The most common situation applies to those with high levels of myopia. The eyeball is elongated, the retina is stretched along the back surface of the eye and thin spots occur. It is these areas of poor attachment that are prone to separation, either spontaneously or as a result of a blow to the head or eyes. Anyone can suffer a retinal detachment from blunt trauma or impact to the eyeball. There is also the theory that the aging process allows for weakness to develop which may lead to detachments.
There are a number of treatments for PVD and RD. These are surgical therapies performed by skilled ophthalmic surgeons who often specialize in retinal procedures. The repair process involves reattaching the separated layers. Cryosurgery uses freezing to c ause scar tissue to form which anchors the layers together and laser "spot welding" accomplishes the same thing. The sooner the repair is done, the greater the likelihood of saving the vision. Even if some vision is lost, it is important to have s urgery to tighten the connections to prevent further separations.
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Additional references: Abstracts: Flashes and Floaters, How The Eye Works (And When it Doesn't), Nutrition, Refractive Surgery (side eff
ects), Spectacle Lenses, EyeCare Reports: Contact Lenses: Multifocal and Bifocals