Presbyopia And Types Of Bifocal Lenses

Presbyopia and Reading Glasses: Options on Bifocal Lenses and Contact Lenses, their types, construction and function.

"To be, or not to be!" If you've answered Shakespeare's pithy declaration in the affirmative and have made it past the age of forty, the next question yielded by life is, "To read, or not to read!" You see (no pun intended), after forty years of age, most people develop presbyopia. Essentially what this means is that the crystalline lens inside the eye, behind the pupil, loses its suppleness and thus its ability to focus for close activities such as reading, sewing, etc.

Everyone knows the remedy for "short arms": reading glasses. But of course, these days it isn't as simple as grabbing a pair of "specs," though many people do this daily at drug store counters across the nation. To have your particular vision needs correctly addressed, it is necessary to have a complete eye exam by an optometrist or an ophthalmologist. Once you have the prescription, you will have to decide on what type of corrective lens is right for you.

Essentially there are four types of lenses to choose from.

The first are single vision lenses, meaning the entire lens is ground to your specific reading power. The advantage of getting them from an optical store as opposed to getting them from the drugstore is that each eye will be prescribed its required power. Though single vision lenses provides the absolute clearest reading field in terms of width and clarity, the drawback is not having distance vision, which means you have to continually take them on and off.

The second type is called a bifocal. It has a straight line, usually, with distance vision at the top and reading at the bottom. Its most glaring incarnation is the executive bifocal, which has something more like a ridge across the entire surface of the lens. Draftsman and people who have to unfurl large blue prints, while having to look up and down, prefer this design. Though there are some round designs, the straight top design, that varies in width from 25 to 45 millimeters, is the most common. This design addresses most general visual needs.

The third type is called a trifocal and, as its name suggests, it has three focal distances. The third focal distance is in the middle and is for intermediate distances not covered by the distant or near vision segments. This design would be more helpful for a typist, say, who has material spread on a desk at different distances.

The fourth type""and one that is gaining popularity, as sterling technology gets better, is the progressive lens. The progressive lens not only renders what is closest to natural vision; it doesn't have visible lines, which make it cosmetically appealing, as well.

All of the aforementioned lenses can be had with a colorful yet utilitarian "tint." Certain colors can be added to the lens to accommodate different work/office/lifestyle situations, even different colored computer screens! Some are even photochromic, meaning they change in sunlight. All of them come in CR-39, a plastic, thus are lightweight. Photochromic lenses, among many others, are only available via special providers. Online contact lens providers are your best bet, as most local branches of eye care companies like Lens Crafters only carry basic CR-39 lenses.

If you absolutely hate "specs," they actually make contact lens bifocals! They come in three types. Some of them are actually designed like the larger lenses, with clearly demarcated far and near visual zones. These are known as alternating vision designs. A second design is called simultaneous and has both distance and near vision zones centered on the cornea. Another is prescribed to be used monocularly, meaning that distance power is put in one eye and reading in the other. The brain somehow knows which one to shut on and off, given one's activity at the time. It takes a bit of work and is not good for everyone, but those who can use them swear by them.

So, there you have it. Me thinks that in days of yore they could do aught but curse the darkness, even with candles lit. But, today, one can use one or a combination of the available technology to make sure that it is, indeed, poor Yorick.

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