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Varifocal glasses, also known as the progressive glasses, graduated glasses and no-lines bifocals are generally used to correct presbyopia and have become one of the most used glasses for prescription as well as designer glasses. The name comes from the fact that the glasses have different power at different levels of the lens. At the top of the lens, the power is minimum, which gradually increases in the middle level and finally, the bottom part of the lens has the maximum power.
It is widely regarded, that the world’s first commercially available varifocal glasses was developed by Duke Elder in 1922 and was subsequently sold by “Gowlland of Montreal”. In 1953, Bernand Maitenaz developed the first modern varifocal lens: The Varilux, which was introduced by the Société des Lunetiers (which later became a part of Essilor).
The greatest advantage of varifocal glasses is the ability to look at objects at varying distances with just a slight tilt of head. As the different levels have different powers, the top part can be used to view objects at a distance, the middle one at the objects at an intermediate distance and the bottom part while working on nearby objects, like reading a book. They also avoid the discontinuities like image – jumps which occur in the visual fields created by bifocal and trifocal glasses. Commercially, varifocal glasses are quite popular too, because of the absence of any line on the lens.
The primary problem with the varifocal lens is its requirement of a careful placement which is related to the user’s pupil centre to generate a distance – viewing reference position. Incorrect specification of this location can cause serious problems which include narrow fields of vision or even clear vision in only one eye. The need to adapt to uncomfortable head positions may also arise, which is unhealthy and risky to the entire body.
Finally, it takes time to adjust to varifocal lens. It may range from few hours to almost two weeks. During this adapting phase, side effects generally include headaches and dizziness.
I was looking for medical benefits of adjustable beds on web and came across researches by expert doctors, their recommendations and health advantages of adjustable beds. I have listed them below:
Dr. Steven R. Garfin, MD, Professor and Chair, Department of Orthopaedics, University of California, San Diego, CA says that What we sleep on can make a big difference in the quality of sleep we get every night.
* The federal Food and Drug Administration, FDA, has recognized that the use of an adjustable bed can help in the treatment of numerous medical conditions. While not advocating adjustable beds as a cure the FDA has cleared the use of adjustable beds for treating minor aches and pains to more serious medical maladies.
* Doctors are of the opinion that Adjustable beds are different than standard flat beds because they allow users to change the incline angle of the head of the bed and at the foot of the bed as well.
* Occupational therapist are of the opinion that slight incline of the head (no more than 45º), coupled with additional support under the knees, can help reduce pain, particularly leg and back pain from herniated discs and/or spinal stenosis.
* It also helps a patient to get out of bed without having to roll and sit up, ease swelling of the legs, ease back pain and offset acid reflux and heart burn.
* They are useful for degenerative spondylolisthesis, osteoarthritis, and any problem with neck, spine and knees.
* Medical adjustable beds are designed to suit the exact requirements of the user like condition of the patient and the exact position the body, simply touching a button.
* They are useful for disabled, elderly and invalid users, regardless of whether the handicap is permanent or temporary.
* The bottom line is, if you do have health problems, or simply want to sleep more naturally, there are few things as effective as adjustable beds.
The upper part of the lens allows clear distance vision and for near vision, the bottom of the lens is used. For clear vision at arms length, the middle of the lens is used.
Using varifocal lenses eliminates the hassle of having to change your contact lenses or glasses for different purposes and allows you to carry on with your day to day activities.
They are especially suited to those who lead an active lifestyle as they are very convenient. For example in the course of one day, you might need to drive, read, go to the supermarket and do work on the computer. Instead of having to change from driving glasses, to reading glasses, and then to everyday long distance glasses, you wouldn’t have to think about your vision at all.
Many jobs involve making quick and frequent changes to focussing on close up objects, to focussing on objects at a distance For example, a teacher needs to see near distances to read text, and write on the board, but must also be able to see to the back of the classroom. Using varifocals would ensure the teacher had clear vision at all times.
It is usually necessary to give yourself time to become used to varifocals. To focus on a certain object, you should move your head slightly until the object becomes clear to you. When driving, it is important to move your head to focus, not just your eyes. It can also be hard at first to perceive the space around you.
This may sound like a lot to become accustomed to, but it only takes a few days to become comfortable with and enjoy the full advantages of your varifocal lenses.
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