Bifocal Lenses contain two different prescriptions in the same lens. The primary purpose of glasses bifocals is to provide the optimal balance between distance vision and near vision focusing needs. Eyeglasses bifocal lenses are available with the reading segments in a variety of shapes and widths including sunglasses bifocal options. The most popular reading bifocal is the Flat-Top (also known as straight-top or D-segment), 28 millimeters wide. Eyeglass Lens Direct offers a number of options for the eyeglasses bifocal lens wearer.
Bifocal Lens Categories
There are two different categories you can place bifocal lenses into; translating and simultaneous. Each lens has multiple designs.
Translating, or Alternating bifocal lenses allow your pupil to alternate between two power segments when you look either upward or downward. Usually the distance power is the upper segment and the near power is the lower segment. For example, if you glance downward to read the newspaper, the lower segment will make the words larger and clear.
Simultaneous bifocal lenses are meant for you to be looking at both distance and near powers at the same time and have become increasingly popular in recent times. There are two basic designs a patient can be fitted with; Aspheric or Concentric.
Aspheric lenses have the different powers blended throughout the lens. They are "progressive" and simultaneous lenses, and the center can be designed for either distance or near powers.
Concentric lenses feature a central prescription of near or far power and are surrounded by a ring or multiple rings of the opposite power. If there is multiple rings, then they alternate between the near and distance prescription. Concentric lenses can be made of either soft or GP materials and location of powers will vary patient-to-patient.
GP,or gas permeable lenses are smaller in size and ride on your eye just above the lower lid, so when you look down the lens stays in place.
Coopervision, a lead contact lens designer company, has created a new hybrid multifocal lens called Frequency55/Proclear Multifocal Lens. It offers a simultaneous effect in combination with monovision and is highly recommended by doctors.
What is Monovision
Monovision is an alternative to bifocal contact lenses and is the idea that one eye is a little better for distance, and the other eye is better for near. Doctors simply fit each eye accordingly, as the most dominant eye is always fitted for distance. It allows a constant clearness in each eye and requires less chair time than bifocal fits. Monovision can be extremely helpful when fitting hyperopic patients, astigmatic patients, younger Presbyopia ones, and patients who aren't good multifocal candidates.
One of the biggest downfalls to monovision is it can lead to loss in depth perception. Another negative feature to monovision is the fact that each eye works separately and not together like normal eyes would. The basic concept of monovision is also used in surgery for Presbyopia. LASIK can be performed with a correction for monovision, and monovision is also used for conductive keratoplasty.
Astigmats and Bifocals
People who suffer from astigmatism generally have trouble wearing a soft bifocal lens because most patients are too sensitive to handle the two extreme power segments in each lens. Bifocals carry a cylinder of 1.00D, but most patients can't even handle half of that. So some would suggest bifocal contact lenses aren't the solution for a patient with a Presbyopia, plus astigmatism but there are options, so if you're a patient with Presbyopia and have a significant amount of astigmatism, you should consider bringing up one of these options to your doctor if they haven't already:
- Use a toric single vision soft contact lens on the dominant eye, and a multifocal on the non-dominant eye.
- If only the non-dominant eye exhibits blurriness, try using a multifocal soft lens in both eyes, or try a toric, single-vision lens in the non-dominant eye.
- Avoid very thin disposable-type bifocal soft lenses and use thicker front-surface aspheric lenses instead.
- Consider a soft bifocal lens that also includes a toric correction.
Options of Bifocal Lens Material
A patient has three options in lens material; GP, hydrogel soft or silicone hydrogel. GP, or gas permeable designed bifocal lenses are the newest technology, and can be made of hard or soft material. Silicone hydrogel is a material that allows a significant amount of oxygen to pass through the lens to reach the eye. These contact lenses are becoming increasingly popular with patients and doctors. Experts expect they will soon takeover traditional hydrogel soft contact lenses.
Are Bifocals Right For You?
Good candidates for bifocal lenses should have a healthy tear system, a cornea that's in good shape, normal blinking rates, and the ability to wear them during most waking hours with comfort. The fittings for the lenses can be long and drawn out, so it's important that you are prepared mentally for this process. You may need to try or test out different bifocal contact lens designs before finding the one that's right for you, but most practitioners have free trial lenses to help you through this process. Good bifocal and multifocal soft lens candidates are people who:
- Require a near Rx of more than +0.75D.
- Are dissatisfied with monovision.
- Have visual demands that require them to see objects simultaneously over large viewing distances such as driving, computer use and reading.
- Want a more appealing alternative to glasses without undergoing refractive surgery.
Advantages vs. Disadvantages of Bifocal Lenses
Some of the advantages of bifocals are good vision at all distances, not carrying around two pairs of glasses, and not having to search for glasses simply to read. Patients report feeling "free" of the heavy glasses, and are able to enjoy activities such as sports easier. The new generation of soft bifocal and multifocal contact lenses have provided acceptable results for many present and future lens wearers, so people who once thought they could never benefit from contact lenses now have a second chance.
However one of the disadvantages to wearing bifocal contact lenses is that it is very likely that they will provide, at a minimum, acceptable vision for all or almost all of the tasks you usually perform on a daily basis. Plus some bifocal lenses are said to cause less contrast sensitivity and poor vision quality.
Cost of Bifocal Lenses
Depending on which contact lens you choose, you could spend hundreds of dollars annually just for the lenses. Most brands offer a box of 4 for approximately $50-$100, but those only last a month. Doctors usually provide free-trial lenses until you figure out which lens is right for you, but keep in mind that's not including doctor visits for fitting, adjusting and follow-ups.
Caring for Bifocal Lenses
If you're using disposable bifocal lenses, caring for your lenses couldn't be easier. You simply follow the instructions that came with the lenses and wear either daily weekly or monthly. For others and regardless of the material, caring for your GP lenses or soft lenses are very similar and usually require the combination of a disinfecting/storage solution and a cleaning solution, or a single bottle of multi-purpose solution for cleaning, disinfecting and storage.
In the past, GP users were told by doctors to rinse the lenses in tap water. Today this is strongly discouraged because of the microorganisms in tap water. You should always wash your hands thoroughly before handling your lenses to prevent damage, scratching, etc. and always store your lenses in fresh solution, in a clean case.