Slaboff/Progressive Lens

[Cowboy]

Howdy All,

I have a patient who, has just returned to my office since her last visit 4 years ago. Her Rx has changed significantly since then. There is no evidence of macular degen., corneal abnormalities, Has the very start of a cataract - no impact, however, the concern, according to the doc is retinal "stretching."

The Quandry!; Her previous Rx, with high index Essilor Natural progressive was
-2.00 -1.50 x 28 -6.50 -1.00 x 150 / 2.00 add ou. Basically a 4.5d difference between eyes. It was discussed with the doc at that time of visit of the possibility of slaboff, but found it would not be necessary. Now with her new Rx:
-2.75 -1.75 X 17 -9.00 -1.25 x 155 / 2.25 add ou. Here we have a 6.25d difference between eyes, contacted the doc again, but this time he is unsure as to the use of slaboff. Should it be considered? With Progressives? What would you do and why?

Thanks for popping by and contributing your thoughts.
:cheers:

Cowboy

[chip anderson]

Ain't likely to work without one. However with an early Cataract developing your results can be erratic and rapidly changing until Cataract is removed. Don't be supprised if you have grief no matter what you do. I have had contact lens patients with same who had been fine for decades and had the Rx change up and down quicker than I could get new lenses made for up to three years before cataract extraction.

[Jacqui]

I would vote for a slaboff. With that much imbalance it should be done even with rapid chnges in correction

[Happylady]

I have done progressives with slab off. The line is very slight.

[hipoptical]

Slaboff if the patient doesn't mind paying for it. She probably would like to see as long as the eye can. Sooner or later, though, it sounds as if it won't matter. Until then, it's best to fulfill your obligation to provide the best vision possible.

[Robert Martellaro]

Cowboy,

I would be concerned that with this level of aniseikonia/induced anisophoria your client might be unable to fuse the different images sizes, or at least sustain fusion comfortably. If she can't, the question of whether to slab or not is moot. Knowing the VA for each eye would be helpful. Try a -2.25 over your clients left lens. Has she always been this anisometropic? I'm curious about what the left Rx was five to ten years ago.

Regards

[Cowboy]

At distance, she is 20/20 - od, 20/30 - os. NV shows that she is at 20/20 - od, and 20/40 - os. Best corrected trial framed for DV. The last 4 years, she has been in the same eyewear (see previous Rx on orig. post). Last couple years, according to her, DV has not been clear and has never been comfortable with reading in any of her glasses. It was not made clear to me how long ago her retinal condition occured, but as it stands now, there are no reoccuring condition(s) and no future procedures in line for this patient.

We have decided to try a pair of slabbed progressives (after discussing all options and opinions with her doc) and see if it does make a difference for her. It may be a costly trial and error, but if it works, I may have a client for life because I paid close attention to certain details that maybe no one else has and she might find it will be the best pair she ever had, or not. Either way, she will have a pair of glasses with the best possible options and care given.
:cheers:

Cowboy

[Specs]

Why not trial frame the patient with the distance Rx and have her look to the extreme upper periphery of the lenses and look in the distance. If any diplopia or ghost imaging is evident, its a good guess that slab-off will be necessary to avoid this when looking down to read.

[Robert Martellaro]

If she's binocular it's a sure bet she'll need a slab or readers, considering that with a reading depth of at least 15mm the prism imbalance at near will be almost 10 prism diopters!

There's still the question of fusion due to the image size disparity, if any. If it's axial length myopia Knapp's law says eyeglasses will minimize the size disparity, maybe. See...

http://www.ncbi.nlm.nih.gov/entrez/q...ctContent-Type:

It's encouraging to know that she was trial framed and that there was little if any adverse reaction to the increased disparity in powers.

Cowboy,

I might do a trial run with a pair of simple segmented bifocals. It will tell you a lot (suppression, diplopia, etc.) and will cost very little for you and your client. Good luck, and let us know what happens.

Regards

[TPL]

Doing this rx in in a lined bifocal might be the best way to aproach this complicated case and evaluate and make changes from there ; almost as a temparary trial case such as we do with contact lenses and advise the patient that changes might have to be made.

[loncoa]

I recommend firstly an aniseikonic grind (this is where the base curves are modified to lessen image size disparity; check with lab) along with the shortest corridor progressive you can get, and slab it. This way the amount of inbalance is lessened due to a shorter distance away from o.c. so you don't need as much slaboff prism. If you do all these 3 things she might be pretty close to happy...:cheers:

[Dave Nelson]

There seems to be little or no reason to use a progressive. As Robert pointed out, the prism disparity is so great, even a couple millimeters will be hard to tolerate. This means that the wearer must go from full distance right to the slab line without use of the intermediate. In between the prism imbalance is likely to be intolerable, and the slab line will be really noticable. This means there is no advantage to the progressive, and a very real disadvantage. I have to respectfully disagree with the premise that the eikonic imbalance can be corrected with base curve differential. The refractive disparity is unusually high, and it seems safe to assume the cause of the myopia is axial. (this explains the retinal stretching.) This means the image disparity is quite probably very significant, and quite probably well beyond the means of using base curve alone, and may require thickness and vertex adjustment to tolerate the aniseikonia. It may also be possible to simply reduce the power in the poorer eye. This may bring the imbalances to within tolerable levels at the expense of a further reduction in the acuity for that eye. (heresy, I know, but it can work, under the right circumstances.) I'm all for progressives and bicentric grinding, but when the disparity is really getting high sometimes we need to look at the two pair one-for-reading-one-for-distance setup as a real option. maybe the KISS theory applies in this case?

[loncoa]

That is of course, one of the options. That being said, the progressive option could have some benefit. Like functioning with one pair. Or possibly using the intermediate, little though it may be. If the patient can tolerate it they have a chance of being happier than if you don't try. Then if they non-adapt, at least ya tried (and you'll get some of your costs back).

[Alan W]

I can't imagine slabbing off a progressive with predictable results. There's no rule for slab line placement that explains how the patients visual behavior can be controlled or enhanced. Think about what you would experience wearing them. At what point would you say you can access it. My sense it would be a disturbance. Conventional methodology is not archaic. It is logical and safe.

[Jim Stone]

Try the progressives with out the slab first. (save the money). There are many people out there reading with one eye that don't even know it. And some by design. If that does not solve the problem, put them in a flat top slab. I think it's kind of dumb slabing a progressive because you can only grind the slab to correct ONE spot. Once they move away from the corrected spot you've lost the bennifit.