Monday, 5 December 2016

A Guide to Occupational Lenses

 What are occupational lenses? 

Unfortunately our eyes weren't designed to read for any length of time and this gets increasingly difficult as we get older. After the age of 40 nearly everyone will need reading glasses. However, if we still want to function normally and read, use a computer,  whilst being able to peer up and see distance objects like clocks and people's faces, then we need a more advanced lens type. Varifocals were often used for this but they were designed before the internet age. They are great for driving or walking around shopping but as they have little intermediate correction they are not very good for computer use. Therefore, for today's digital world lens manufacturers have come up with "Occupational" or "Indoor" Lenses.

Occupational lenses are a type of varifocal lens that are designed to suit a specific task, such as working at a computer in an office environment.

Normal Reading Glasses
Traditional reading glasses are clear at our normal reading distance of approximately 40cm. However, in today's modern world we often have to read at arms length or further due to phones, tablets and computer screens. With a normal varifocal lens there are three useful parts in the lens, these being the distance part, the intermediate part and the near part, found in the top, middle and bottom of the lens respectively. Typically a normal varifocal lens is set up to favour distance vision and near vision, and the intermediate part of the lens is quite small. This can be a disadvantage for anyone who spends a lot of time at a computer screen as it restricts the position from which a screen can be viewed clearly, and means that the wearer must keep their head in one place.

To overcome this difficulty, the occupational lens, also known as an indoor lens and as a degressive lens, increases the size of the near and intermediate parts of the lens. To do this it usually sacrifices some or all of the distance prescription.

Add Power 60
The Hoya Add Power 60 is a degressive lens that sacrifices all of the distance prescription in order to get the best possible vision in the near portion of the lens out to a distance of sixty centimetres, which is a typical computer screen distance. This lens is ideal for a job that requires a lot of reading and computer screen work, but little else.

Tact 200
The Hoya Tact 200 and Tact 400, also sacrifice the full distance prescription to maximize the near and intermediate parts of the lens, but in this case they allow clear vision out to 2m and 4m respectively. The Tact 200 would be ideal for someone working at a computer in a smaller office area, and the Tact 400 might be used by someone working at a computer in a larger, open office.

 Great for wearing indoors 

Great for reading music
For those people who want the advantage of a degressive lens, but without completely sacrificing the distance part of the prescription, Hoya supply the Workstyle range in 200 and 400 versions. These are lenses that maximize the near portion of the lens and the intermediate portion of the lens out to either 2m or 4m, like the Tact lenses, but which also retain a small portion of the lens for the full distance prescription. This offers an excellent solution to the requirements of office work, but because the distance portion of the lens is smaller than the intermediate and near portion, these lenses should not be used for driving. However, many people find them great for hobbies such as reading music or sports such as golf and shooting.

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