A bifocal lens only allows you to have two vision distances (near and far) while progressive lenses give you all your range of vision from distance, intermediate and near in a smooth progression. Most people like the newer technology of the progressive because it allows for more natural vision and cosmetically they look nicer because there is no line. The upside to standard lined bifocals is that the peripheral vision is sometimes better.

A progressive lens make a progressive change from distance vision to near vision providing an infinite range of powers in between. An additional advantage of progressive lenses is the lack of a bifocal line.

Yes, not all frames are doable with Bifocals or Progressive. The lens height of the frame should be at least 30mm. We want to make it easier for you to identify which frame can or can't be done with Bifocal or Progressive by putting a check or cross mark on the item page. If you need more advise, please don't hesitate to contact our Customer Service Department.

Progressive" is an political term used loosely to identify activists of the left, favorable to sound and fair economic and social policies, equality of chances, and the defense of personal rights. The European Tribune is broadly progressive, but welcomes all contributors regardless of political self-identification, provided that they be respectful of the mission of this site, provide principled disagreement and don't engage in trollish behavior. (click to see the definition of a troll)

The lens is the part of the eye that helps focus light on the retina. The retina is the eye's light-sensitive layer that sends visual signals to the brain. In a normal eye, light passes through the lens and gets focused on the retina. To help produce a sharp image, the lens must remain clear.

A lens implant (intraocular lens or IOL) is a man-made, clear plastic lens approximately 6 mm in diameter which is placed inside the eye at the time the cataract is removed. It replaces the natural lens and remains permanently within the eye. The lens has small spring-like arms called haptics that prevent the lens from moving out of place.

Variblee rate springs defelct at different amounts per inch. An example would be: 200 lbs. = 1 inch deflection, 600 lbs. = 2 inch deflection, 1000 lbs. = 3 inch deflection, and so on. Varible coils have a soft initial spring rate and a much firmer spring rate to handle more weight, decrease sway, and improve handling.

Research indicates that only a small number of those with drinking problems will experience a progressive decline. An individual's drinking pattern frequently ebbs & flows over time. While "not drinking" may seem an unpleasant choice to someone who is currently a frequent and heavy drinker, research clearly indicates that even those labeled "alcoholic" have periods of normal drinking or even abstinence under the right conditions - if they so choose.

The LENS Low Energy Neurofeedback System provides feedback to the brain in the form of an extremely weak electromagnetic field, similar in power to the one that surrounds digital watches. Although the feedback signal is weak, it results in a measurable change in the brainwaves, all without conscious effort from the individual receiving the feedback. The unique LENS procedure creates a highly personalized and detailed plan that accelerates the training process.

There are lens implants, which give focus at all distances. There are limitations and you should consult with your surgeon about them.

Short answer is no. The conjunctiva, the tissue that covers the white part of the eye (the sclera) forms a cul-de-sac between from the edge of the cornea to the eyelid margin. Sometimes a contact lens, especially a soft contact lens may roll up and become difficult to find. An eyecare practitioner will be able to locate the lens and remove it.

Our otoscope lens uses between a 3x- 4x magnification. We use the same magnification and focal length as the standard Welch Allyn? otoscope. We actually used their lens as our prototype when developing our otoscope. We figured they have been around for over 100 years and are the leading manufacturer of otoscopes in the world today and would be our best guide to what the optimum magnification and focal length should be.

Spectacle lenses are made of two main types of materials - plastic or glass. Plastic lenses are often CR39 or polycarbonate. Both main materials come in a variety of refractive indexes, designed to minimise the thickness. HiIndex lens materials are commonly 1.56, 1.60 and 1.67, as compared to 1.523 for common crown glass. The refractive index of plastic lenses is capped at around 1.74, whereas glass lenses range up to an index of 1.9, making them potentially thinner.

Since edge thickness is a function of lens power, centre thickness and curvature of the front and back curves (all inter-related) the edge thickness is influenced by the following features:

Color is a personal choice and doesn't affect how well the lenses protect your eyes from UV light. Gray and brown are popular because they distort colors the least. Athletes may choose other tints for their color-enhancing properties; for example, yellow lenses are popular with skiers and target shooters because they work well in low light, reduce haze, and increase contrast for a sharper image.

Chemical coatings on lenses can do a number of things: anti-reflective coatings increase the transmission of light through the lens; scratch-resistant coatings prevent scratches; mirror coatings reflect intense glare away from the eyes. All coatings increase the value and versatility of your sunglasses.

Answer: -- A Barlow lens is a lens that you use with your eyepiece. A Barlow lens will double (2x Barlow) or even triple (3x Barlow) the magnification of any eyepiece that you attach to it. To use a Barlow lens, remove the eyepiece from the focuser, insert the Barlow and then insert the eyepiece into the Barlow. Remember, though, that a Barlow is best used with low magnification (long focal length) eyepieces.