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A variable corridor progressive lens is an advanced type of no-line multifocal lens. In this design, the length of the "corridor," which is the transition zone between distance and near vision, is not fixed. Instead, the length can be adjusted to fit the specific height of the eyeglass frame you choose. This ensures that your reading zone is always in the correct place.
read more about variable corridor progressive lens ...The corridor is the invisible channel that runs down the center of a progressive lens. It is where the power gradually changes from your distance prescription at the top to your reading prescription at the bottom. This area provides your intermediate vision for things like computers and dashboards. The length of this channel is critical for visual comfort and how easily you can find your reading power.
In the past, progressive wearers were limited to large frames. If they picked a small frame, the reading part of the lens would be cut off. Variable corridor technology solves this problem. It allows an optician to select a short corridor for a narrow, stylish frame or a long corridor for a large, classic frame. This means you can choose almost any frame style and still get a full, working lens.
The length of the corridor changes the visual experience. A longer corridor allows for a smoother, more gradual change in power, which often provides a wider intermediate zone for computer use. A shorter corridor changes power very quickly. This allows you to reach your full reading power with less downward eye movement, but it can sometimes cause slightly more side distortion.
Variable corridor lenses are made using "free-form" or digital surfacing technology. Unlike older lenses that were made from pre-molded pucks with a set design, these lenses are cut precisely by a computer. The software uses your prescription and your specific frame measurements to calculate the exact corridor length needed to give you the best possible vision.
Changing the corridor length has a direct impact on "swim," the sensation that the world is moving when you turn your head. A shorter corridor packs all the power changes into a smaller vertical space. This concentrates the distortion at the sides of the lens, which can increase the swim effect for sensitive wearers. A variable corridor design allows the optician to elongate the channel as much as the frame allows to minimize this dizzying sensation.
Generally, a longer corridor is more comfortable because the transition is softer. However, if you choose a small frame, you must use a short corridor. Your optician will help you balance frame size with visual comfort.
Yes. Variable corridor designs are typically found in premium, digital progressive lenses. They are more expensive than standard, fixed-corridor lenses because of the advanced technology used to make them.
This is the smallest vertical measurement a frame must have to hold a progressive lens. Variable corridor designs have reduced this number significantly, allowing progressives to fit in much smaller frames than before.
When you are shopping for glasses, tell your optician if you prefer small, narrow frames. They can recommend a variable corridor progressive lens that is designed to work in that specific shape. They will take a measurement called the "fitting height" to ensure the corridor length is customized exactly for your eyes and your chosen frame.