Testing monofocal IOL outcome using smartphone
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It's not a perfect method but one can surely get a good idea of what vision will be like with different IOL settings. All you need is a very good smartphone with a good camera that has MF (manual focus). Stand far away from written text and focus your camera to perfect focus using the PRO manual focus setting. Then you can move your smartphone to closer objects and the focus will remain fixed at "plano". Look at your watch and it will be a blur. Look at something 1m away and it is a little blurry but still acceptable.
Now to simulate -1D adjust the manual focus on until the smartphone has perfect focus on written text 1m away. With the focus fixed at 1m you can easily see your watch at 40cm from the smartphone and see relatively good in the distance although not perfect. To simulate -2D close vision you have to focus your camera manual setting to perfect focus at 50cm. Reading is then exceptionally good, intermediate a little blurry and distance a complete blur.
This has helped me a lot to understand what the IOL eye will see at different distances. It looks like -1D is totally under rated in the community. With -1D in both eyes one will absolutely not need to ever wear glasses, but one will have the option to put either distance glasses or reading glasses on for prolonged driving or reading. Also, with -1D, progressive glasses will be extremely thin and light as the correction for far and near will only be +-1D top and bottom of the lens.
Remember your smartphone has to have an exceptionally good camera with MANUAL FOCUS setting to simulate what an perfectly implanted IOL with zero astigmatism will see. Although not a perfect test in any way, it will certainly help everyone to understand what they can expect to see at different distances should they use standard monofocal IOLs.
0 likes, 11 replies
RonAKA peterfox
Posted
That is an interesting way of looking at it, and simulating the impact of degrees of myopia. I think to do it most accurately the phone camera would also need to be capable of setting the aperture as well as the manual focus. Aperture has a major impact on depth of focus. A f/16 setting for aperture will bring things into focus from quite close to infinity. However a f/1.4 aperture has a very narrow depth of focus and at even an intermediate distance the distance will be out of focus as well as up close.
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To my personal thinking selecting a -1.0 D myopia lens in both eyes is kind of a split the baby solution. You are not going to see well at distance, and not very well up close for reading text, or an smart phone either. My thoughts are that having a -1.0 D residual in the non dominant eye and as close as possible on the -D side for the distance dominant eye is a much better solution. Distance will be fine, but it is still not crisp for reading, and the non dominant eye at -1.25 to -1.50 D is likely to be a better compromise.
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That said it is a personal choice and there are many options with pros and cons. At the end of the day each person has to make their own choice on what works best for them.
peterfox RonAKA
Posted
Hi Ron. Yes the Pro setting on good camera smartphones has all the settings like aperture, ISO, white balance.... All the other settings should be left in AUTO mode and only the MANUAL FOCUS should be adjusted.
This idea was introduced to me by a very highly regarded surgeon whom has suggested that after many years his patients are mostly satisfied with -1D mono focal IOls. Thereafter using progressive glasses is not as bothersome as the range is only +-1D.
I can't remember now, is it not you that can see down to 18 inches with your mono focal than landed plano? Now Imagine how much clearer that close vision would be if it was another 1D closer.
Yes you are correct that distance vision would not be perfectly crisp but for indoor daily life it should be just fine. Going outside glasses would be necessary for perfect vision. Reading will also require glasses most likely.
-1D according to my ophthalmologist give the patient functional vision at all distances without glasses, whereas setting plano in both eyes you cannot quickly grab your phone without getting readers. This is approach is only meant for patients that has no interest in monovision like myself as he says if you are playing ball sports monovision is a definitive NO-GO as depth perception is compromised. He said the depth perception issues are normally not an issue for patients whom are not into ball sports when the monovision is less than 1D.
All said, I remain confused and I'm still learning towards -0.5 D target. Definitely do not want any multifocal.
RonAKA peterfox
Posted
I currently have simulated monovision with my left non operated eye with a residual -1.25 D myopia. That is one step away from -1.0 D. When watching my UHD 65" TV at a distance of about 7 feet I can see the puck in a hockey game perfectly with my 0.0 D IOL eye, but I would never see it with the -1.25 D eye. But with both eyes open, I see the puck and the play just fine. I'm sure if both eyes were -1.0 D I would need glasses to watch hockey comfortably on a big screen TV only 7 feet away.
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I have been simulating monovision now for about a year using a contact in my non IOL eye. With no contact I have about -2.0 monovision. I have tried a -0.5 contact to give me -1.5 D monovision, and a -0.75 D contact to give me -1.25 D monovision. I do not like the -2.0 D monovision. I find it leaves a significant hole in good vision at a close intermediate distance of 12-14 inches or so. The -1.5 D monovision is definitely better for close vision, but still seems to leave a bit of a weak spot right at my computer monitor distance. I have not tried a -1.0 D solution as the sweet spot seems to be between -1.25 and -1.5 D. I'm sure it would give me better distance but weaker close vision. -1.25 lets me read my iPhone 8+ quite easily at 12" or so. I am about 99% convinced I will ask for an IOL monofocal lens that corrects my left eye to the range of -1.25 to -1.50 D, when it comes time to do the cataract surgery on it. And if there is a decision to be made, I would prefer closer to -1.25 over being closer to -1.5 D.
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As far as loss of depth perception or loss of stereoacuity, I have not noticed anything significant. There was a full report on the internet that was very informative. The full report seems to have been taken down, but there is still a summary which can be expanded, along with the tables and figures. You can expand the text under these to get a better explanation as well. They seem to have taken people who had both eyes fully corrected for distance with monofocal IOLs and then applied a series of add lens of +1.0, +1.50, and +2.00 D to test their vision. This is basically how defocus curves are done. With the lens variations they tested visual acuity at the various distance and also stereoacuity (depth perception). What they basically found is that both 1.5 D and 2.0 D monovision gave acceptable across the range vision, the 2.0 D caused significant loss of stereoacuity. The considered the gain of stereoacuity of 1.0 D insignificant over the 1.5 D. But there was a significant loss of close vision with the 1.0 D monovision. Out of all this they concluded that -1.5 D of monovision or anisometropia was optimum. In looking at their data and my personal experience, I have concluded that -1.25 is even better than -1.5, and I find the reading quite acceptable with it. There is a lot of good information in this report and the graphics. It is worthwhile spending some time on it, as it clearly shows what monovision can do and can't do. Here is the name of the report to search for.
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semanticscholar Optimal amount of anisometropia for pseudophakic monovision
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My other thought is that monovision has probably gotten a bad reputation by trying to go for the now outdated full monovision of 2.0 to 2.5 D of anisometropia. I can see no reason to shy away from -1.0 D (micro monovision) or up to -1.50 (mini monovision). And as I said in the first post I don't see any advantage in having both eyes myopic. With my -1.25 monovision I am eyeglass free for all distances except reading very small print especially in dimmer light. I have progressives, but only use them to give my eye a rest from having the contact in. I also have some +1.25 readers which I use occasionally for really detailed close work. This effectively gives me about a +2.5 D add in my left non IOL eye, and a +1.25 D add in my IOL eye. Close vision is then excellent, but I seldom need it.
Koshkaboo RonAKA
Posted
This is interesting. Almost 2 weeks ago I had the Vivity lens put in my right eye with a target of around -.025 D. I see 20/25+at distance as of the end of last week and can see at computer distance (although a slight strain). I can read my phone and most print although I would not want to do it for long without light reading glasses (1.25 seems about right).
My left eye has the RXSight Light Adjustable lens in it (5 days ago). The target initially was -1.0 D. We know that I will adjust it a little more myopic than that. Typically they expect to get good computer vision at -1.25 D although it can vary. I suspect based upon what I see now that I will end up with getting that eye to -1.5 D although it will depend where I am about a month after surgery.
rick18299 Koshkaboo
Posted
I'm curious... Why did you choose the RxSight LAL for your second eye?
How have things worked out for you now, after 9 months?
I'm anticipating having cataract surgery in a few months and I am weighing the RxSight versus the Tecnis Eyehance IOLs.
Bookwoman peterfox
Posted
To simulate -2D close vision you have to focus your camera manual setting to perfect focus at 50cm. Reading is then exceptionally good, intermediate a little blurry and distance a complete blur.
That may be the way it works on a phone, but not for this human. I'm -2 in my right (dominant) eye and -2.5 in my left, after surgery. Distance is not a complete blur at all. In fact if I had to, I could drive locally on roads I know well without glasses (although of course I never would.)
peterfox Bookwoman
Posted
Hi bookworm.
My apologies as I didn't state that I was referring to reading. The eyechart that I use during the tests becomes a complete blur at distances further than 3 meters when the Manual Focus is set at 50cm. You are correct when viewing roads and cars at -2D on the phone is still looks like driving would be possible.
Bookwoman peterfox
Posted
Ah, yes, reading is a complete blur at that distance!
lucy24197 peterfox
Posted
Thanks for the camera suggestion. Everything you can learn helps with your decision, but regretfully nothing can really predict how exactly your vision will end up.
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I've got mini-monovision with my recent cataract surgery. I had a -1.75 target in my near eye, and based on my depth of field it seems to have ended up pretty close. Tonight I threw on an old pair of glasses that provide 0.75 correction for distance to see what -1.0D would look like.
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One very important thing to consider is where your vision was before you got cataracts. What you're used to can make a difference in what you'll be happy with. I've had natural mini-monovision for decades and have only worn glasses for driving. The first doctor I saw recommended -1.0D for my distance eye. Looking back over many years of prescriptions, my distance eye has been -0.25 to -0.5 for most of my glasses-wearing life. Using the glasses tonight to simulate a -1.0 target showed that would have made me REALLY unhappy unless wearing glasses all the time except for doing intermediate work--I'd feel like the whole world was just a little blurry, because I've been used to better vision than that. As far as reading goes for -1.0D, for me, even if a document is held out as far as my arms can reach, text is still a little blurry. My husband has always been somewhat farsighted. Given the way he fusses if his distance vision is down to 20/20, I KNOW he'd hate -1.0D. If I'd started with eyes that were more myopic -1.0D might be fine, but from where my eyes and vision have been historically, it would feel like a loss and I'd be unhappy with it.
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Everyone's eyes are different; you may have a completely different experience. I have a -0.5D in my distance eye and I think I made the best decision for me. I will say that for a couple days after surgery my distance vision was better than it is now, and it was really nice. There are some things that are quite frustrating now that it's settled in to -0.5--I can't quite make out the description of a tv program when I hit the info button for my tv (12' away), and I could right after the surgery. But I've got unhealthy eyes and am having some complications so it might improve. Someone with healthier eyes might have better results in general. Text on paper is blurry any closer than 30-36" or so with my -0.5D eye. Computer monitor would be too blurry with my distance eye alone, but it's great with both.
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rick18299 peterfox
Posted
How far away would -0.5D focus sharply using this phone method?
Is there a chart somewhere showing -diopters to focal distance?
RonAKA rick18299
Posted
Your just divide 1 meter by the defocus D value to get the optimum visual acuity distance. Some examples:
-0.5 D = 2 meters
-1.0 D = 1 meter
-1.5 D = .66 meters
-2.0 D = 0.5 meters
and so on...
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One thing to keep in mind though is that vision does not drop off a cliff as you go away from the optimum distance. You need to look at a defocus curve to see how much it drops off in both directions. When you offset the lens the whole curve moves by the amount you offset it. Google this to see a couple of monofocal lens defocus curves as well as the Vivity and Eyhance.
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