Posted , 4 users are following.
so assuming that an edof lens is mono, what is happening on the lens to create the increased depth? does the power increase reside more on the center or on the edges? thank you
0 likes, 10 replies
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soks Dapperdan7
Edited
edof is basically a low add bifocal and that low add gives you intermediate. that is for symfony and lara. vivity has a wavefront technology whatever that means but it has basically 3 concentric circles and one of them is giving you low add intermediate. eyhance is not an edof but a monofocal plus it has a low add central 1mm diameter zone giving some intermediate.
RonAKA soks
Posted
I am not so sure a true EDOF is similar to a "low add bifocal". When you get a bifocal or trifocal add to an IOL you will see peaks in visual acuity at closer distances. An EDOF is different in that it stretches the primary focal point to intermediate distances. You can see the differences in a defocus curve. An EDOF will have a curve that is reduced at the primary focal point but does not drop as fast as the distance gets closer. A bifocal or trifocal will have a primary peak and then one or two additional peaks which will not likely be as high as the primary one, but are enough to see at closer distances.
RonAKA Dapperdan7
Edited
A monofocal that is aspheric brings all the light to the same focus point. An EDOF stretches the focus point out by various means. It extends the depth of focus but also reduces your distance vision to some degree. Depending on the method used to stretch the focus point there may be side effects like halos or flare of the light.
soks RonAKA
Posted
edof with refractive rings is a failed experiment. zeiss lara for example has a 0.9 and 1.9 add. why would anyone need a 0.9 add? and the rings bring on all the nighttime fireworks.
the general idea for edof is that there is no drop from distance to however you get at near. not worth it in my opinion.
trilemma soks
Posted
A 0.9 D add would be good for seeing your feet and the path in front of your feet while walking.
soks trilemma
Posted
doesnt monofocal give distance to 4-3 feet?? shouldnt that be distance from head to feet? so why is 0.9 needed?
Dapperdan7 RonAKA
Posted
how about a spherical monofocal? doesnt that also bring all light to the same focal point?
RonAKA Dapperdan7
Edited
Spherical (non aspherical) IOLs are considered older technology because they do not bring all the light to the same focal point. As a result they do have an EDOF type of effect. They probably give as much extension of depth of focus or more than the Eyhance lens. They can be less expensive than an aspheric monofocal, and kind of a "poor man's" EDOF. Like the Eyhance they don't provide the 0.5 D minimum extension that is required to sell the lens as an EDOF. They are in a grey area between aspheric monofocal and an EDOF.
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It is interesting that you can find articles from 10-15 years ago debating the merits of aspheric over spherical lenses and not everyone agreed that aspheric was better. But, they now kind of dominate the market. The Tecnis 1, AcrySof IQ, and Clareon are all aspheric. Some other lenses in this grey area are the B+L enVista, and the Rayner EMF.
Dapperdan7 RonAKA
Posted
gotcha. just duckduckgo'd it and never realized the original lens was not perfectly spherical. thank you
trilemma Dapperdan7
Posted
RonAKA was not saying that. Instead I think he was saying that not correcting astigmatism may have some EDOF type of effect.
You understand that "spherical" in lenses is not the same as that word in mathematics.