Any Eyhance Experience Like This
Posted , 4 users are following.
I was reading posts on another forum and a person with Eyhance in one eye (other eye not operated on) posted the following: “Do you have any plausible explanation why my operated eye with the IOL sees better sharpness and contrast in low light conditions (e.g. twilight or evening) vs. bright sunny weather or well-lit rooms?” The Doctor on that forum replied “It would need to be related to pupil size.” The Doctor also stated his practice had no experience with Eyhance. The person who posted the question was also having other problems with that eye, but it didn’t sound like it was related to the lens.
I know there have been one or two posts on this forum with “similar” comments about the Eyhance. One person posted on a sunny day in order to see a sign clearly in the distance they needed to turn their head slightly. Has anyone else with Eyhance experienced this or similar? Has anyone read any research on this?
I was strongly leaning towards getting Eyhance and I have read a lot of positive outcomes with Eyhance on this forum, but after reading experiences like this it makes me hesitant.
2 likes, 12 replies
Spoo karin08666
Edited
I would speculate if your pupil gets very small during bright days, the central 1-2mm part of the iol which has -0.5D power shift in the center of the visual axis takes over and you need to "watch around it" to see distance properly and push past the -0.5D shift. I would imagine the Vivity (or any edof) has a similar property if your pupil gets small enough. I'm not sure what the critical size threshold for the pupil is where this becomes a significant issue.
This is a concern for myself as well, but i'm not sure if my pupil size would still have a similar issue. I found the discussion you are referring to and this would be a fairly plausible explanation for the patient's issue. His pupil size would be of a lot of interest.
RonAKA karin08666
Posted
The strategy that Eyhance uses to stretch the depth of focus is to vary the power of the lens from the centre out to the edge. For that reason the depth of focus effect is going to depend on the pupil size which is directly dependent on the light level. I have not looked at the lens closely enough to determine whether the shift in power dependent on the pupil size (light level) is toward a closer focus or a more distant focus. For reading in dimmer light, like a menu in a dim restaurant, one would want it to shift to a closer focus. But, to see the side of the road at night one would want it to shift to more distant focus. Seems like a conflicting requirement. As I say I simply don't know which way it shifts.
Spoo RonAKA
Posted
The center of the lens is -0.5D, so the smaller your pupil gets, the more myopic you get compromising your distance vision.
karin08666 Spoo
Posted
I read a study awhile ago that had one line in it saying the Eyhance was pupil dependent. I haven't been able to find anything else since. Not sure how big of a problem this can create, but I would think it would be annoying. I could never get used to wearing progressive glasses, so I also wonder if my brain would have problems adapting to this change in vision in the center of the lens, or if it would be like bifocals, which I have worn for a number of years.
karin08666 RonAKA
Posted
I know how big my pupil size is from when I got my eye measured, but not sure how small it gets. Plus, will it continue to get smaller with age. As you have indicated in some of your posts the intermediate range you receive with the Eyhance isn't a lot, so I am now wondering if it is worth the chance. Or because it is such a small intermediate change if I might not even notice it or if I will be one of those people that do. As I've heard someone say on this forum before "if you could only try before you buy".
RonAKA Spoo
Posted
I guess it would be all relative to what the lens was targeted to overall. If you were targeted to +0.25 then I guess it would switch to plano at distance when the pupil closes down. I would think in all outdoor activities during the day the pupil must be pretty much at minimum. The myopic shift may then be offset by the pinhole effect of the small pupil. And in my example of a dimly lit restaurant or driving at night in the country then vision would switch to be more myopic and would suffer some.
RonAKA karin08666
Posted
Keep in mind that a 0.25 D shift is a very minor amount. That is at the limit of what can be measured for a difference.
RonAKA karin08666
Posted
I have not researched the pupil thing much, but I know the maximum pupil size decreases with age. Not sure if the minimum pupil size changes with age, or just stays the same.
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On the Eyhance I would look at it an extension of the depth of focus of somewhere around 0.35 D. The slope at which vision decreases with closer distance is less. So there is no real intermediate boost as such, just a slower decrease as distance gets closer.
karin08666 RonAKA
Posted
If I go with the Eyhance my left eye target will be -.25. So if I am understanding what you said correctly, when I am in bright light and my pupil constricts, I will then be -.50 in that eye? So does that mean I go from seeing 4 meters down to 2 meters? That is a huge difference. I must be misunderstanding something.
RonAKA karin08666
Posted
I have not researched the Eyhance to the degree that I could comment with reliability on this aspect of it. I have not seen the data that @Spoo is quoting for the center of the lens being -0.50 D. I have just looked at it from the perspective that the Eyhance has a lower and flatter peak in visual acuity, along with a modest extension of the depth of focus. If I was considering the Eyhance I would target peak vision with the distance eye at plano. The normal practice is to aim a little low at -0.25 just as a margin of safety away from from going into the positive zone. Going there will start to reduce your close vision and you may be giving away all of the extended focus you get with the Eyhance. If one targets -0.50 then distance vision will suffer some, but close vision will be a bit better. When using monovision I see no point in compromising distance vision in the distance eye, as close vision will be provided with the close eye.
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With the close eye the normal practice with a monofocal would be to target -1.5 D to give good reading vision. If one was to use the Eyhance instead it could make sense to back off to -1.25 D to take advantage of the depth of focus extension and get a similar close vision as the monofocal at -1.50 D. Or, one could do the full -1.5 D and get better close vision than the monofocal would provide.
karin08666 Spoo
Posted
I am trying to understand the distance that -0.5D gives you, or takes away with a smaller pupil. I don't have a huge understanding of these diopters and defocus curves, but if my surgeon targets -0.25 in my left eye and my pupil shrinks and I am using the -0.5D center of the lens, how much distance will I be losing? -0.25 is 4 meters and -0.50 is 2 meters. Doesn't make sense I would be losing that much distance vision. What are your thoughts on this.
Spoo karin08666
Posted
I think distance isn't that important in this scenario. What is important to understand that if your pupil is very small, like 2mm in full daylight miosis, then a significant portion of the incoming light will go through the center part of the lens and your distance vision quality will be significantly impacted because it's like looking at your distance vision wearing minor readers. That's why also some surgeons I see online using eyhance as the monovision lens while using zcb00 as a distance lens in the dominant eye for people with small pupils.
It's likely this scenario isn't that severe for people with 'normal' sized pupils as your eye gets light also from the peripheral parts of the lens. Otherwise you'd have a lot of unhappy patients out there.