|
| Shady Grove Eye and Vision Care Dr. Alan N. Glazier Optometrist |
| For Appointment or General Info, Contact Us At: |
| 15200 Shady Grove Road Suite 100 Rockville, MD 20850 Tel: (301) 670-1212 Fax: (301) 216-9692  aglazier@youreyesite.com |
Bifocal and Multifocal Eyeglass Lenses
BIFOCALS When two prescriptions come in one lens, it is called a bifocal. The
term bifocal means literally "Two Focuses". It is meant to describe
eyeglass lenses that enable the user to see clearly at two different distance
ranges through one lens. Benjamin Franklin is credited with inventing the first
bifocal lens by gluing two lens halves from different prescriptions together.
Bifocals are used for many reasons, but the main reason is Presbyopia ,(see
section "why my arms are getting shorter"or "presbyopia") a
condition that affects every adult above the age of 40 years. Presbyopia is
when the human near focus system gradually becomes unable to focus on objects
that are closer in. At that point, the prescription that helps people to see
objects clearly at distance is no longer sufficient to see close objects also.
Bifocals have an additional power on the bottom part of the lens to aid close
focus in presbyopic people so they can see far and close with one lens Some
people who are young can see far away and close with one prescription, then as
they age, it becomes necessary to have an addition in power in the bottom of
the lens. Bifocals come in many shapes and styles:
A blended bifocal may be any of the above lenses where the line is blended out,
leaving a blurry area across where the old line was. A blended bifocal is not a
multifocal or progressive lens .
Multifocal lenses
Like bifocal lenses, multifocal lenses are used primarily to help Presbyopic people focus at distance and near with one lens. Multifocal lenses have no segment and no lines in the lenses; the power from the top of the lens to the bottom is smoothly transitioned from distance viewing power through near viewing power as the user looks downward through the lens. Multifocals have the advantage of offering clear vision over a large range of distances, not just two distances, so multifocal users can see, far, mid-range (computer screen distance) and near all in one lens with no line. Multifocal lenses come in many designs and styles. Typically the multifocal lenses that are the easiest to adapt to and have the widest mid-range and reading areas are more expensive, ranging in cost from $200 to $400 for both lenses. For people who have not had success adapting to multifocal lenses, it is important to know that there are four factors that determine success in multifocal adaptation:- Brand of Multifocal - Higher-end multifocals are much more successful than lower-end multifocals and can make the difference between adaptation and non-adaptation.
- Multifocal measurement and pupillary distance - measurements for multifocal lenses must be taken by a trained professional. Make sure the optical centers of the frames are properly marked, the pupillary distance (distance from center of one pupil to center of the other pupil) is measured monocularly and binocularly (for each eye individually and together). Improper measurements taken for multifocal lenses are the most frequent reason for non-adaptation.
- Frame measurement - frame measurements are sent into the laboratory properly and frames are adjusted properly on patients face before marking optical centers of lenses.
- Patient motivation - often patient motivation is the determining
factor in adaptation to these lenses. If you take the time and wear the lenses
regularly without switching to an old pair or giving up, you can adjust.
Remember, there is an adjustment period for bifocal lenses also, so which type
of lens will you spend your time adjusting to? If a patient puts their time and
effort into adjusting to progressive multifocal lenses, they probably will
never have to be in a bifocal ever! Why? Because the power in a progressive
multifocal lens can be adjusted over time, just like a bifocal lens.
A multifocal lens gradually changes curvature, thus power As you go towards the bottom of the lens. The sides Outlined are areas where vision may be warped or Distorted due to the severe curvature change; The center areas are where vision is clear; distance At top parts of lens, midrange in middle and near Towards the bottom. See bifocal, blended bifocal, blended bifocals, multifocal lenses, no line bifocal, no line bifocals, no-line bifocal, no line bifocals, zeiss, zeiss progressive lenses, zeiss no line bifocals, varilux, varilux progressive lenses, varilux no line bifocals, progressive lenses, progressives, presbyopia, bifocal contacts, bifocal contact lenses, contacts, contact lenses, acuvue, rockville eye doctor, rockville, eye doctor, optometrist, opthalmologist, ophthalmologist, optician, optical, rockville optical, germantown optical, potomac optical, gaithersburg optical
