Results 1 to 2 of 2

Thread: Fixed Focal length add powers

  1. #1
    Bad address email on file
    Join Date
    Apr 2002
    Location
    St. Cloud, MN
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    25

    Question Fixed Focal length add powers

    Hello all,

    I'm wondering if anybody can help me determine an appropriate add power for patient needing to work at a fixed distance of 19 inches. Patient's RX is OD +1.75 +.50 x15, OS +1.00 +.50 x80. Prescribed reading add is 2.75. Patient needs a round add power in the upper corner of OD lens and will be using it monocular to read instrumentation at 19 inches. I know Xcel's Acclaim series of trifocals uses a 61% intermediate for pilots working at a similar distance. Wondering if anybody has the formula handy that can help determine appropriate upper add power in this scenario.

    Thanks in advance

  2. #2
    OptiBoardaholic
    Join Date
    May 2000
    Location
    B.C. Canada
    Occupation
    Dispensing Optician
    Posts
    1,189
    If the patient is an absolute presbyope, you need only calculate the dioptric value of the distance. Since 19 inches is about half a meter, you need a lens with a focal length of about half a meter: +2.00
    It is always a little easier to work in the metric system, since dioptors are metric based, and calculations can be carried out simply by moving a decimal place.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Corridor length change in free-forms
    By rdcoach5 in forum Progressive Lens Discussion Forum
    Replies: 10
    Last Post: 03-03-2007, 11:29 AM
  2. axial length
    By cdavis6632 in forum General Optics and Eyecare Discussion Forum
    Replies: 2
    Last Post: 07-13-2006, 12:29 AM
  3. Prism only in the Bi-focal
    By ziggy in forum Ophthalmic Optics
    Replies: 11
    Last Post: 09-20-2005, 08:27 AM
  4. A gradient-index liquid crystal lens with a tunable focal length invented
    By Joann Raytar in forum General Optics and Eyecare Discussion Forum
    Replies: 5
    Last Post: 09-08-2004, 07:43 AM
  5. Aspheric Tri-Focal???
    By Mike Fretto in forum Ophthalmic Optics
    Replies: 1
    Last Post: 06-23-2000, 07:31 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •