The Bifocal and Progressive Bifocal Options for 1.67 and 1.74 High Index Lenses
Aging has many effects on the body including vision. Just as the skin and tendons start to lose their elasticity, so does the lens of the eye at around the age of 40. This makes the lens less flexible and reduces its ability to properly focus on close objects. This condition, called presbyopia, affects everyone when they get older.
The first symptoms of presbyopia include difficulty reading small print. People will find they can’t read newspapers or books unless held at arm’s length. Other symptoms include headache and eye fatigue when reading, writing, and doing other tasks that require focusing on anything close to the eyes. As the condition progresses, people are forced to get corrective lenses. For those who have no other vision problems, presbyopia will require they carry reading glasses with them.
For those who have a preexisting vision condition requiring corrective glasses, their vision will also require correction for presbyopia. Some people cope with this by carrying two pairs of glasses. One for reading and seeing objects close up, and another for seeing farther away. However, switching back and forth between pairs of glasses is inconvenient, and a more practical solution is using bifocal lenses. Bifocals have two lenses, one for close-up vision and another for distance. The far distance lens is larger and is located above the close-up vision lens.
If bifocal lenses conjure up images of Benjamin Franklin, don’t despair because you have another option called progressive bifocal lenses.
Progressive Bifocal Lenses
With simple bifocals, you have two distinctly different lenses in which one is set inside the other. This makes it noticeable to other people. Simple bifocals also provide only two vision “settings,” the near field (for reading) and the far field. When your eyes move between the two lenses, you will notice an abrupt change as your eyes adjust.
On the other hand, progressive bifocal lenses aren’t made up of distinct lenses set inside the other. Instead, the lens gradually changes from the near field to the far field with all the intermediate “fields” in between. This means there’s no sudden “jump” or transition between near and far field when you look up from a book to view distant buildings on the horizon.
There is another advantage of progressive bifocal lenses over simple bifocals. Bifocals allow you to see clearly in the near field and far field. However, when you get older, your eyes will begin to have difficulty seeing the middle field (objects at arm’s length). Progressive bifocal lenses also correct for the middle field while bifocals do not. Without progressive bifocals, you would have to get trifocal lenses.
Because progressive bifocal lenses aren’t made from separate lenses, there are no distinct lens boundaries that others can see. To them it appears you are wearing a single vision lens. If you require a high prescription, progressive bifocal lenses are available for 1.67 and 1.74 high index lenses. However, the simple bifocal option is only available for high index 1.67 lenses.
As with everything, progressive bifocal lenses have some disadvantages. When wearing these lenses, you will notice some aberrations on the periphery of your vision. This produces a slight blurring effect when looking far to the left or right in the lower part of the lens. In years past, this effect was more pronounced than it is now. Future lens improvements will continue to reduce this effect. You can adjust to this by turning your head a bit to better see objects on the periphery. Another problem is that the continuous transition from near to far field will take a bit of getting used to for some people.
In summary, progressive bifocal lenses have both an aesthetic advantage over bifocals and a practical one in that they correct your vision for all distances. As technology improves, the disadvantages of progressive bifocal lenses will be reduced further. If you have questions about selecting the right lenses for your needs, contact us here.