Announcement

Collapse
No announcement yet.

Prism trouble shooting question

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    #31
    Originally posted by Elvis Is Alive View Post
    No, I am aware of the supreme brittleness of 1.74.

    It has more to do with me. Personally I don't like fit a drill mount in very many RX's above 4 diopters unless it is a small eyesize or the decentration is quite small.

    I'll have a long conversation with someone if they insist on a drill with high plus/minus.
    My -9.50 Silhouettes in 1.74 look amazing. Just saying.
    I'm Andrew Hamm and I approve this message.

    Comment


      #32
      my bad I meant lower index
      Last edited by ChrisBowers; 08-07-2023, 02:17 PM. Reason: wrong

      Comment


        #33
        Originally posted by AngeHamm View Post
        My -9.50 Silhouettes in 1.74 look amazing. Just saying.
        Amazingly thick.

        Comment


          #34
          Originally posted by AngeHamm View Post
          My -9.50 Silhouettes in 1.74 look amazing. Just saying.
          If you like it, that's all that matters I guess...

          Comment


            #35
            Duplicate
            Last edited by NAICITPO; 08-08-2023, 11:42 AM. Reason: I'm the worst

            Comment


              #36
              Originally posted by luka View Post
              Excuse me as it's my first reply. If reducing the prism is absolutely not an option based on the optom, the trivex would be the way to go to reduce the transverse chromatic aberration.

              Based on the article Robert linked, for a plano polycarb lens with 2Δ, we have a colour spread of about 0.067D. Going to a 4Δ lens in 1.67 we have about double, or 0.125D, which is the problem. 1.6 won't solve the problem (0.111D @ 4Δ) but trivex gives us only 0.093D, only 1.5x more than in the poly lens. So assuming everything is pretty much equal between the old glasses and the new except for the prism, trivex would be the choice to go for if you're doing a remake.

              Cosmetically it'll be thicker yes. Sometimes I discuss with patients and get the lab to narrow drill mount lenses by a mil or two which could save you some of the nasal thickness. I would agree with Kwill about ordering the 70.5 PD.
              Agree with DRK great post, please post more!

              For those that don't know where the 70.5 is coming from:

              PD's from pupilomters are 33.5/34.5. According to System for Opthalmic Dispensing you take the amount of prescribed prism and multiply it by 0.3. 4 prism diopters x 0.3 = 1.2. For BI you add the 1.2 onto each individual PD, for BO you subtract.

              R = 33.5 +1.2 = 34.7
              L = 34.5 +1.2 = 35.7

              Total of 70.4.

              Comment


                #37
                Originally posted by drk View Post
                Well, then don't just dog me...give me your take.

                (After you get a coffee. You're cranky again.)
                Yep, it’s like Kwill is trying to channel Chris in a grating way. To each their own.

                Thumper comes to mind, and I’m not heeding his advice right now.

                And you wonder why I’m not as active here as I used to be. Too much personal opinions, not enough advice.

                I’ll return to my dark space now.
                I bend light. That is what I do.

                Comment


                  #38
                  Please dont let other posters affect your participation. I rarely visit the site but has a lot of great info.

                  Originally posted by lensmanmd View Post
                  Yep, it’s like Kwill is trying to channel Chris in a grating way. To each their own.

                  Thumper comes to mind, and I’m not heeding his advice right now.

                  And you wonder why I’m not as active here as I used to be. Too much personal opinions, not enough advice.

                  I’ll return to my dark space now.

                  Comment


                    #39
                    Originally posted by AngeHamm View Post
                    My -9.50 Silhouettes in 1.74 look amazing. Just saying.
                    I've done that but at least one eventually cracked. I wouldn't warrant it in a notch or drill.

                    Originally posted by ChrisBowers View Post
                    my bad I meant lower index
                    Or better still, higher Abbe value.

                    Originally posted by NAICITPO View Post
                    For those that don't know where the 70.5 is coming from
                    Light is deviated 1cm at a distance of one meter. The distance from the center of rotation of the eye to the cornea, about 13.5mm, plus the vertex distance, about 13.5mm, averages 27mm (the stop distance), hence a deviation of about .27mm per diopter of prism. Adjust the fitting point for all meridians of prescribed prism.

                    Best regards,

                    Robert MArtellaro
                    Science is a way of trying not to fool yourself. - Richard P. Feynman

                    Experience is the hardest teacher. She gives the test before the lesson.


                    Comment

                    Working...
                    X