Acuity and Depth of Focus are interesting
Posted , 8 users are following.
As my cataract surgery draws near, I have been starting to test my vision so as to be able to assess the results of the surgery. I currently have "super monovision", with my good eye at +0.25 D, and my cataract eye at roughly -8.0 D. I'll be getting a new Light Adjustable Lens (LAL) in the cataract eye only, likely targeting one or two diopters of myopia for more effective regular or mini monovision.
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I have been thinking simplistically that I would be happy with J1 reading vision in my new artificial near-vision eye, and figuring that would leave me at something like 20/70 at distance for that eye. With my good eye still at 20/20, that seems like a very satisfactory outcome.
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However, using my printed Jaeger chart, I find that I am able to read J1 already, with my good eye. That's with good indoor lighting and with some difficulty, but I can read J1 accurately at any distance from about 10" to 15" from my eyeball. That surprises me, because at my age I don't believe I have any significant focal accommodation - the data I've seen says that accommodation is generally close to zero by age 60, and I'm pushing 65.
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What I do have is small pupils, measured at 2.9 and 3.0 millimeters. I don't know whether that is scotopic or mesopic or what, so I have no objective standard to compare. But my doctor did say that my pupils are small, as pupils go. And small pupils are known to produce greater depth of field in vision. Is that why I can see both 20/20 and J1 with my aged eye?
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I am left somewhat confused about my goals for the upcoming cataract surgery. Since the operation will be on my near-vision eye, I think I should aim for better near vision than I already have in my distance eye. But J1 is pretty good - how much better can I reasonably hope for? J1 plus? Logmar zero? Maybe I should be thinking about reading J1, but with dimmer light or with less effort - how hard are you supposed to try? If my goal is an "easier" J1, then it's something I can't measure - I would like to measure and track numerical results, but maybe I need to be satisfied with something as subjective as "It feels ok." Or "it doesn't seem that good." Perhaps I should just ask the doc to add nearsightedness until my computer screen (at arm's length or intermediate distance) starts to look blurry, and accept whatever near vision that gives me.
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Any ideas or observations would be welcome.
0 likes, 23 replies
Guest phil09
Edited
If you are -8 uncorrected that means that you are extremely near sighted right? Which it why you can read J1 without accommodation. If you are wearing glasses or contacts to correct that eye for distance I would assume that you can no longer read J1, Small pupils do help. I think -1.5 might be enough for more tasks in generally good lighting (not for dim light though).
phil09 Guest
Posted
Yes, -8 D is very nearsighted, and I can easily read very small print with that eye, the cataract eye. As you suggest, that's no surprise.
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What surprised me is that I can read J1 using only my naked +0.25 D eye. I'd have thought that I'd need the focal accommodation of a much younger man to read J1 with a near-plano eye. But apparently not. I never wear any eyeglasses or contact lenses.
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Perhaps I do have a small amount of accommodation left in my eyes. As I look a little further into the internet, I do see some presbyopia curves that indicate a half diopter or so of accommodation persists from age 65 even to much older ages. Still, I wouldn't think that's nearly enough to get me to J1.
Guest phil09
Edited
Oh sorry for misunderstanding. Yes you should be very presbyopic by now but… who knows. I'm guessing that is in really good light? I have one IOL set for distance (Eyhance) and it had a prediction of -0.21 SE and landed at -0.125 SE (so basically bang on plano) and it can read J1 in really bright light (like a sunlit room with a lot of windows)… which also shouldn't be possible. But it drops off quickly as I walk further away from the windows. I think I have small pupils too. And maybe my brain is just good at processing the "data". I think the thing is that there is a lot more to the entire visual system than just the refraction of an IOL and the defocus curve and no one really knows why one person gets a great result and another doesn't. When they say "your mileage may vary" it can vary by a lot.
Dapperdan7 phil09
Posted
how have you tolerated the difference between an +.25 and a -8.0 eye? that seems difficult. and you say you dont wear glasses or contacts?
phil09 Dapperdan7
Edited
I tolerate it just fine - no difficulty whatsoever.
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I first got my monovision about 28 years ago with LASIK. My eyes were about plano and -1.50 D respectively, with little or no astigmatism. A cataract has induced increasing nearsightedness in my -1.50 D eye - I started noticing it about three years ago, and now it's around -8.0 D. My distance eye still gives me pretty good vision from about one foot to infinity, and I can still read fine print up close with my nearsighted cataract eye. So I can see pretty much everything, with one eye or the other. No corrective lenses needed.
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I can't really relate to people who have problems with different focal lengths for the two eyes, though I can of course sympathize. I attribute my successful tolerance to two things: First, I was introduced to monovision at a relatively young age, in my mid thirties - it's often easier to teach a young dog new tricks. And second, the difference between the eyes increased very slowly due to the cataract effect, so acclimation was slow and easy. Like putting the frog into comfortably warm water before gradually boiling it. I am just full of pithy metaphors today.
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I'm no expert, and my experience is just one anecdote. But it does make me wonder about people who decide that they can not tolerate monovision - maybe if they gave it more time, they could tolerate it fine. Starting young might also help, but by the time you have cataracts, that ship has already sailed. (Apparently I had one more metaphor left in me!)
soks phil09
Posted
what were your pre cataract prescriptions?
phil09 soks
Edited
Plano in my distance eye.
-1.50 D in my near-vision eye. The cataract has induced much greater nearsightedness in recent years, bringing me to about -8 D now.
(My astigmatism was largely corrected by LASIK many years ago, so little or none remained.)
RonAKA phil09
Edited
I suspect your natural lens eye without the cataract still does have some significant accommodation, and that combined with a smaller pupil is giving you the extra depth of focus. Is there any astigmatism? That can help some too.
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The accommodation will be gone of course when the LAL is implanted, and since you have the opportunity you will be able to refine it to what you want. I would suggest the real test is no the Jaeger test in sunlight or very bright light, but it will be more what you can see in dimmer light conditions. In dimmer light the pupil opens up and you lose that pinhole boost in vision.
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Have you been screened for the LAL procedure yet? I recall that a small pupil was one of the contradictions as they need a minimum of I recall from the video of about 6.5 mm with dilation drops to do the light adjustments on the lens.
phil09 RonAKA
Posted
Well, I'm not getting an LAL in the good eye, so whatever accommodation exists will remain for a few years (I hope). I suppose the good distance eye will work together with my new near-vision LAL eye to provide satisfactory reading vision for a while. Then when the distance eye goes bad someday, I'll probably need to rely on the near eye alone for reading vision, so I'll want to make sure I get sufficient myopia and/or depth of focus in that eye now, even at the sacrifice of some distance vision.
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I did have -1.25 D of astigmatism in the good eye at my most recent refraction. I guess that's enough to help with reading a little bit. Spherical equivalent would be a little negative, when combined with the +0.25 sphere.
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I did not notice any screening specific to LAL. I'm assuming my eyes dilate normally and the iris can expand to the necessary size. If it turns out that assumption is wrong, that will be disappointing - dunno what I would do next.
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Merry Christmas, everyone!
RonAKA phil09
Posted
Yes, SE will be -.375 which will help with near vision combined with the remaining accommodation.
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It is a quick check to fully dilate your pupil with drops and measure the pupil size.
Dapperdan7 RonAKA
Posted
ron, does not a pinhole pupil boost depth of field but also restrict light? so how is that a boost in vision as you say? thx
RonAKA Dapperdan7
Posted
If there is lots of light a pinhole will increase depth of focus and can make an out of focus lens sharper. That is why a quick and dirty test by the optometrist is to look at the eye chart through a paddle that has pinholes in it. If vision improves that indicates the current lens is not optimum and can be improved with a correction.
judith93585 phil09
Edited
I can relate to your post. The target for my L eye was -1.5D and R eye was -1.0D. Now that all is said and done, I can read better with my R eye.
I chose what might be micro-monovision to minimise the difference between my eyes. That said, I do have a feeling that my L eye sometimes does not contribute to my visual acuity. I fell yesterday which concerns me because I have osteoporosis ...
Lynda111 judith93585
Posted
,Judith
I am sorry about your fall, especially on the day before Christmas. You certainly don't want to have depth perception issues. and be at risk of falling with osteoporosis. Take care of yourself.
RonAKA judith93585
Posted
If you can read better with the Right eye I would question whether it is really at -1.00 D. In this range of -1.0 to -1.5 D vision should be very good at the distance to the feet with good 3D vision.
judith93585 RonAKA
Edited
Thanks Ron. It wasn't a matter of looking at my feet. I lost my balance and fell at home.
soks judith93585
Posted
i missed a step 2 months after my symfony implant. its was a getting used to issue for me.
judith93585 soks
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Thanks soks. Could repeat the last sentence? I'm not sure I understand.
soks judith93585
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two months after my first surgery i missed a step and stumbled. it was probably because i had not gotten used to the new vision.
jo61855 judith93585
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Hope you are okay. What time of day did this fall happen, what were you doing (your condition), where in your home did this happen? It's important to analyze the circumstances and develop coping or preventative measures. Be well.
RonAKA judith93585
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I am sorry to hear that. Hope it was not too serious. I am finding balance to be a problem too, and I suspect more related to age than vision. I thought I was going down on several occasions when decorating the Christmas tree this year while standing on a stool to reach the top. I think it is time for a shorter tree!
judith93585 jo61855
Posted
Thanks jo.
judith93585 RonAKA
Edited
Thanks Ron. Bruises and soreness, hoping no broken bones.