Mixing IOLs
Posted , 5 users are following.
As a potential monovision choice, is it possible to mix enVista monofocal near vision with a Tecnis monofocal for distance?
0 likes, 6 replies
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Notes on Mixing IOLs
Lynda111 sarahsouth
Posted
It's possible, but why would do it?
Guest sarahsouth
Posted
Mix and match is fine but it depends on the surgeon. Some have no issue with it or even use it as a strategy… others are totally against it.
RonAKA sarahsouth
Edited
It certainly is possible but I think for mini-monovision you would be better off with enVista in both eyes. The Tecnis 1 lens probably has the least depth of focus for a monofocal, while the enVista has the most. More depth of focus is better with mini-monovision.
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Choosing the correct targets and actually achieving them is the most important factor in getting the most out of mini-monovision.
Dapperdan7 RonAKA
Posted
a few questions:
is the depth of focus difference between different monofocal brands around a half a diopter at most? and would that be around 20" or 1 meter or 3.28 feet?
does the DOF extend both toward distance and near?
and would a monofocal set with less DOF mean wanting closer refraction targets than one that has more?
would you say the difficulty people have with adapting to monovision is when the distance between lens does not allow of overlap?
finally, depth of focus is always at some cost to visual acuity, correct? and a lens that leaves the natural spherical aberration mostly intact in the cornea will be best for DOF and worst for acuity, correct?
RonAKA Dapperdan7
Edited
If you google enVista and look under the Aberration Free Optic section there is a graph of how B+L says depth of focus and visual acuity is impacted by the residual positive spherical aberration.
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You can see from the graph that the Tecnis 1 has the least depth at about 0.55 D, the AcrySof (or Clareon) is next at about 0.80 D, and the enVista has most at 1.1 D depth of focus. It is not shown but I believe a spherical lens is at about 1.2 D.
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As you can see from the graph the visual acuity goes down as the the spherical aberration increases. B+L claim that they have picked the optimum point of the trade off between gain in depth of focus and loss in visual acuity.
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Measured in diopters the depth of focus has no specific distance. It depends on what the target is for the lens. Yes it extends in either direction, but when the lens is targeted for distance, there is no meaning to depth of focus beyond infinity, only as you go closer.
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Yes, the Tecnis 1 lens is the most demanding on accuracy of refraction, being centered in the eye, and free from tilt of the lens. It is also more sensitive to damage to the cornea. The enVista is a more forgiving lens.
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If the targets are set to far apart in mini-monovision there are two issues. One is that there can be a dip in visual acuity where the distance one is dropping off before the near eye is making up for it. There also can be a loss in 3D vision in the same zone. The recommendation is to have no more than 1.5 D between the eyes. If your distance eye ends up at -0.25 D, then you could go to a max of -1.75 D in the near eye. -1.50 D would give more of an overlap though.
sarahsouth
Posted
Thank you all for your thoughtful advice.