Results 1 to 15 of 15

Thread: Slab off - Textbook vs. real world

  1. #1
    OptiBoard Professional William Walker's Avatar
    Join Date
    Jun 2005
    Location
    Jacksonville, FL
    Occupation
    Dispensing Optician
    Posts
    297

    Slab off - Textbook vs. real world

    I have a patient who we'll call Sue. Sue's Rx:

    OD -4.75 -0.50 x 015
    OS -1.50 -1.75 x 106 Add 2.25

    The doc asked me to do a slab off, and the Rx seems like it definitely warrants one. We made a proceed 1.67 with Crizal with slab, and cosmetically they look beautiful. The patient tried them for about a month, and couldn't get used to the slab at all. The distance was fine, she said, but the near would only come in clear if she occluded one of her eyes.

    Her old Rx is:

    OD -5.00 sph
    OS -1.75 -0.75 x 106 Add 2.00

    She's brought them back now to be made without slab. What could I have done differently?

    The few very experienced opticians I consulted with before making these said the slab was the only way to go, and in the State Board review, prof Joe Simmons says bar none we should be making slabs for anyone with 1.5D or more difference at 90, yet it seems that when I do, the patients won't accept it. What gives?
    William Walker

    Associates in Science in Opticianry
    Associates in Science in Optical Business Management
    Licensed Dispensing Optician
    Board Certified
    Certified Paraoptometric Assistant
    American Board of Opticianry Advanced Certified
    National Contact Lens Examiners Certified

    Next Goal: ABOM

    Optician with Lenscrafters in Jacksonville, FL

  2. #2
    Master OptiBoarder
    Join Date
    May 2000
    Location
    Fayetteville, NC, USA
    Occupation
    Dispensing Optician
    Posts
    2,009

    Habitual Imbalance

    This patient has probably been experiencing this imbalance for some time. If so, they have either been supressing or alternating at near and have adapted to the compromise. I suggest they will eventually be able to handle it if the slab is configured correctly given time. My colleague, Prof. Simmons would agree that slabbing should be considered at 1.5 but typically is only significant at 2 prism diopters of imbalance. Good luck with this one.

  3. #3
    OptiBoard Professional William Walker's Avatar
    Join Date
    Jun 2005
    Location
    Jacksonville, FL
    Occupation
    Dispensing Optician
    Posts
    297
    wmcdonald,

    How long would I have to estimate for a patient would this adaptation need to be? She's had them for a month already before telling me she just wants to go back to a regular, non slab lens.
    The biggest problem I have is that this patient complains of getting headaches within just afew minutes of wearing, so it'd be very hard to get to her to wear this pair only for best adaptation.
    Is there anything that could be given to slowly break a patient into their Rx, as with latent hyperopes?

    Thanks for the reply
    William Walker

    Associates in Science in Opticianry
    Associates in Science in Optical Business Management
    Licensed Dispensing Optician
    Board Certified
    Certified Paraoptometric Assistant
    American Board of Opticianry Advanced Certified
    National Contact Lens Examiners Certified

    Next Goal: ABOM

    Optician with Lenscrafters in Jacksonville, FL

  4. #4
    Master OptiBoarder
    Join Date
    Jun 2000
    Location
    California
    Occupation
    Dispensing Optician
    Posts
    2,817
    How high is the seg? Where is the slab line? How deep is the frame?How much prism was ground?

  5. #5
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    As far as a 1.50 D cut-off goes, I generally wouldn't worry too much about slab-offs below 2.00 D of imbalance, and many labs would also be reluctant to surface once below this since it is more difficult to get a good slab-line.

    As for this particular patient, did she have a multifocal of some type before (I'm assuming so with that add power)? Was she previously symptomatic without the slab-off? Finally, are you certain that her symptoms are a result of the slab-off prism?

    Keep in mind that it is not uncommon for spectacle wearers to adapt to even significant amounts of prism imbalance, particularly if they've had the condition for a while. Though even some of these wearers may experience slightly more comfort or better binocular acuity at near with the prism correction. Your doctor can take near phorias through a trial frame correction in order to determine whether vertical imbalance may be a concern (the lenses should be taped off to force the wearer to read below the optical centers). When in doubt, you are still better off ordering a slab-off correction when you think the situation warrants it, even if the wearer ultimately prefers to go without it. Clinical studies have shown that about 60% of anisometropes will generally prefer the prism correction, whether they are symptomatic or not.

    Best regards,
    Darryl

  6. #6
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    9,388
    Her vertical imbalance should be about 4 pd BD OD. If she doesn't have some kind of kooky vertical phoria that serendipitously needs 4 pd BD, she is unlikely to have been fusing at near, and as Wm. said, was probably suppressing (this is easy to check in the clinic). With enough prism, she could be not suppressing any longer, and feeling the strain of vertical vergence, especially if you undercorrected the imbalance. (P.S.: how much slab off did you use? 2D, I'll bet. Progressives aren't helping her, here, BTW.)

    My advice to you:
    1.) If she was asymptomatic, and especially if you tried 3 pd slab off or more, I'd go back to her habitual situation.

    2.) If she was symptomatic, I'd try up to 4 pd slab off.

    My question to the board:
    I would always do a segmented MF fit high with slab off. Are you all progressive cowboys, or am I unaware of the success rates out there? Nonetheless, why force the patient to depress 16-18 mm when you could have them depress a measly 8-10?

  7. #7
    Pomposity! Spexvet's Avatar
    Join Date
    Jul 2004
    Location
    On my soapbox
    Occupation
    Dispensing Optician
    Posts
    3,760
    Keep the slabbed-off lens, you may end up needing it, after all. ;)
    Good luck, I've been there.
    ...Just ask me...

  8. #8
    Pomposity! Spexvet's Avatar
    Join Date
    Jul 2004
    Location
    On my soapbox
    Occupation
    Dispensing Optician
    Posts
    3,760
    Quote Originally Posted by drk
    My question to the board:
    I would always do a segmented MF fit high with slab off. Are you all progressive cowboys, or am I unaware of the success rates out there? Nonetheless, why force the patient to depress 16-18 mm when you could have them depress a measly 8-10?
    I'd consider the lens design that the patient had been wearing. Yippee yi-o ky-ay (sp?) isn't my style.
    ...Just ask me...

  9. #9
    OptiBoard Professional William Walker's Avatar
    Join Date
    Jun 2005
    Location
    Jacksonville, FL
    Occupation
    Dispensing Optician
    Posts
    297
    The patient has been in progressives for a number of years before she came to us. She says she can read fine out of her old glasses, so I was doing the slab in an effort to give her more than what she came in asking for, but now I feel like I've given her more headaches than she bargained for.

    My biggest fear was how she was going to accept the cosmetics of the line, but with the AR, once the patient had it on, you couldn't see the line, even if you were looking for it.
    William Walker

    Associates in Science in Opticianry
    Associates in Science in Optical Business Management
    Licensed Dispensing Optician
    Board Certified
    Certified Paraoptometric Assistant
    American Board of Opticianry Advanced Certified
    National Contact Lens Examiners Certified

    Next Goal: ABOM

    Optician with Lenscrafters in Jacksonville, FL

  10. #10
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    If she doesn't have some kind of kooky vertical phoria that serendipitously needs 4 pd BD, she is unlikely to have been fusing at near, and as Wm. said, was probably suppressing (this is easy to check in the clinic).
    While it's certainly possible that she is suppressing her vision in one eye as you say, I've seen references to studies that reported asymptomatic vertical prism adaptation of up to 5 prism diopters in some anisometropes, and adaptation to 2 diopters of vertical prism within just a few minutes (often with only 1/2 diopter of measured vertical phoria). I wonder how many refractionists actually attempt to measure the vertical phoria at near through anisometropic prescriptions like this?

    Best regards,
    Darryl

  11. #11
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    9,388
    What's a refractionist? An autorefractor? If there is such a bird, they certainly wouldn't be checking something like that!

    ("This message brought to you by the American Optometric Association")

    But seriously, if you have something odd like that in your chair, you'd darn sure better'd figure out what the situation is, or you're in a heap of trouble.

  12. #12
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    What's a refractionist?
    It's seven words less than "ophthalmologist, optometrist, ophthalmic optician, or ophthalmic medical technologist." ;)

    Best regards,
    Darryl

  13. #13
    Master OptiBoarder Clive Noble's Avatar
    Join Date
    May 2000
    Location
    Israel
    Occupation
    Optical Retail
    Posts
    429
    We also have been providing Slab-Offs for many years for anything with a 2 dioptre or more vertical differential, but over the last couple of years there have been a few rejections.

    We decided on a policy; if the Pt hadn't had a S-O before and the new diff was only marginal, we would try making the glasses without, however, if there was a problem, we would redo it for the cost only of the slab.

    In nearly every case the Pt has not needed the slab.

    Now, on a personal note, I've always had about 1.50 diff between my eyes and never needed a slab off, but over the last few months the dreaded cataract is progressing on one eye together with big black floaters and a detached vitrous. The difference is now 2.50 and I made a pair of PALs only to reject them after 2 minutes and return to my old fuzzy specs.
    I couldn't take the diplopia

    The following morning I tried them again and 'BINGO' no problem, just a bit of discomfort when going from the top to the bottom of the lenses, but
    NO DIPLOPIA.

    The interesting thing is when I take them off, and either raise or lower my eyes, (with no glasses) I get diplopia (the other way)...... the brain is already programmed.

    I've been wearing them now for 2 months and am already needing a change in the rogue eye, the difference is now getting on for 3.00D

    Watch this space, I'll keep you informed

  14. #14
    Master OptiBoarder Darryl Meister's Avatar
    Join Date
    May 2000
    Location
    Kansas City, Kansas, United States
    Occupation
    Lens Manufacturer
    Posts
    3,700
    The interesting thing is when I take them off, and either raise or lower my eyes, (with no glasses) I get diplopia (the other way)...... the brain is already programmed.
    Welcome to the wonderful world of prism adaptation. ;)

    Best regards,
    Darryl

  15. #15
    One eye sees, the other feels OptiBoard Silver Supporter
    Join Date
    Jul 2002
    Location
    Wauwatosa Wi
    Occupation
    Dispensing Optician
    Posts
    5,458
    Quote Originally Posted by Clive Noble
    We decided on a policy; if the Pt hadn't had a S-O before and the new diff was only marginal, we would try making the glasses without, however, if there was a problem, we would redo it for the cost only of the slab.
    That's generally how I handle it, essentially "if it's not broken, don't fix it" solution. Make sure that the client understands the situation; if there has recently been some reluctance in performing prolonged near tasks it may very well be due to an increase in VI. The client may attribute this to aging or health problems and neglect to mention that there is a problem. Sometimes the changes are so gradual it may be hard to say that there is a problem. In general, if there are frequent and/or prolonged near tasks I would seriously consider a slab or a separate pair of reading glasses.
    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.



Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Replies: 0
    Last Post: 06-29-2004, 03:41 PM
  2. Replies: 0
    Last Post: 03-15-2004, 05:16 PM
  3. The Holiday Season Around the World
    By Clive Noble in forum General Optics and Eyecare Discussion Forum
    Replies: 1
    Last Post: 12-17-2003, 04:17 PM
  4. Replies: 0
    Last Post: 06-27-2003, 05:47 PM
  5. Did we witness the start of the LAST World War?
    By hcjilson in forum Just Conversation
    Replies: 15
    Last Post: 09-17-2001, 08:50 AM

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
  •