im sure it has been discussed many times before but why is a target missed on an optical outcome? if a plano lens is placed and the result is +.25 hyperopic, it theoretically cannot be the lens but what are the variables involved in the result?
that does make sense in making the lens choice to leave room for error.
so another quick question. i have been experimenting with mini mono vision on and off enough to understand the pros and cons but..l have distance (plano) in my dominant left eye which seems to have a bit worse of a cataract (i observe this by switching eyes when looking at lights etc) and experimenting with -.75 to .1.50 on my right eye. would this also play into my choices of iol power for mini monovision, as the difference between the two would invariably grow larger once cataracts are removed, the left eyenow unencumbered with worse cataract and seeing much better?
so many questions and variables. and everyone will have different results....life is a crapshoot
Something seems to have been messed up with the format of your post. Probably worthwhile posting it again as at least on my computer much of it is cut off. Guessing that you are asking why targets are missed I will give you some thoughts on that.
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It can be issues with the measurements, the formula method used by the surgeon, and variables in how the lens is implanted in the eye. The best measurements are probably done with a IOLMaster 700 instrument. The best formulas are the Hill-RBF 3.0 and Barrett Universal II for myopic eyes prior to surgery. And implantation is up to the skill of the surgeon. If you have difficult eyes (very high myopia or hyperopia, or prior refractive surgery like Lasik) then the ORA process which is a measurement of the eye after natural lens removal during cataract surgery, may be of some help.
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And overall the surgeon should learn on the first eye. Normally the target on the first eye would be for distance with a target set at -0.25 D or a bit more to allow for error not making you go hyperopic. Then after a full recovery of 6 weeks the outcome can be measured and used to adjust the formula for the second eye, which would normally be -1.50 D on a SE basic for mini-monovision.
im sure it has been discussed many times before but why is a target missed on an optical outcome? if a plano lens is placed and the result is +.25 hyperopic, it theoretically cannot be the lens but what are the variables involved in the result?
- The eye is a complex living thing with many soft tissues. Even blinking can change the tear film cells on your eye and affect your vision. It doesn’t take much. It’s a game of micrometers.
- The target is based on a mathematical guess so there is room for error there as well.
- The implant is much smaller than a human lens. Imagine the size of a small jellybean vs. a dry lentil. So the implant may settle into a position that’s slightly anterior or posterior of the lens plane. Even a fraction of a millimetre forward or back will make a difference.
so another quick question. i have been experimenting with mini mono vision on and off enough to understand the pros and cons but..l have distance (plano) in my dominant left eye which seems to have a bit worse of a cataract (i observe this by switching eyes when looking at lights etc) and experimenting with -.75 to .1.50 on my right eye. would this also play into my choices of iol power for mini monovision, as the difference between the two would invariably grow larger once cataracts are removed, the left eyenow unencumbered with worse cataract and seeing much better?
Depending on the lens, a 1.5D offset could actually be plenty for a mini monovision setup. It depends on the lens and your goals etc. A lot of people do pretty well (not perfect as perfect does not exist… they still need readers in some situations) with Vivity with just a 0.5D offset. That’s because that lens already has some extension of focus depth build it (with some trade off in terms of contrast sensitivity)
Now I see the whole questions with thanks to @david98963, I really don’t have much more to add to my original response to the reason for error in the outcome, other than there may be some error in the IOL itself. Some manufacturers claim that “the other guys” have errors in their lens powers. Not sure how significant it really is though.
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On the mini-monovision simulation you need to correct one eye to plano as best you can. The other eye you under correct it to leave you at -1.50 D myopic. The cataract compromises this somewhat as your visual acuity will be impaired by it. However the power differential has no reason to change when you get IOLs. The surgeon should give you -0.25 or slightly more in the distance eye, while leaving you at -1.50 D in the near eye. That should be quite similar to what you see with contacts fitted to give you the same differential.
Consider the surgeon’s confidence & ability to achieve intended refractive goals based on patient corneal irregularities, ocular pathology, the aberration profile of the selected IOL and patient tolerance to neuroadaptive, depth of field, & visual acuity issues. The IOL calculations alone are predictive and not absolute to the other variables involved in an IOL outcome including the attitudes and expectations of the patient