The chart was a response to AnomalyChick's comment regarding myopic people seeming to have a larger depth of focus, but that she didn't have any scientific evidence of that.
Unfortunately such studies only deal with averages and say nothing about what any one particular person's depth of focus will be like, so you don't need to understand the details if you aren't interested in the topic.
Good light makes a difference mostly since the more light the more information data the eye receives to try to sort out what it is seeing. However as the doctor notes, a smaller pupil does increase depth of focus so light does help for that reason as well.
Eye's usually rely on accommodation to focus at different distances and therefore don't need a large depth of focus. Since most IOLs can't accommodate, they are designed with optics that try to make up for that with various techniques to increase the depth of focus (/depth of field, both phrases are used since increased depth of focus leads to increased depth of field). e.g. beyond the typical multifocals there are new IOLs designed to provide even larger depth of focus that aren't yet approved in the US, like the Symfony I went abroad to get and the IC-8 which uses the pinhole effect to increase depth of focus. (the Symfony uses diffractive optics to elongate the depth of focus, along with chromatic aberration correction).
Obviously it would help after accommodation declines for the natural lens to have a larger depth of focus, but for whatever reason it didn't evolve that way. Its likely there wasn't much evolutionary pressure for larger depth of focus, or for accommodation to last longer, since most of the loss occurs after the typical reproductively active years are over. A change improving later life vision's effect on survival of its gene line could only be very indirect via longer lived elders increasing survival odds of the young they already had, but of course before modern medicine humans less often lived long enough to have lost all accommodation so there was even less reason for evolution to have addressed the issue.
So is that part of the reason that good light makes such a difference? What causes the greater depth of field of an IOL over natural lens? Thanks to all for the added comments. Software Developer -the chart was a little too technical for me to understand how the depth of focus affects functional vision.
One of the most important factors post catarct with monofocal IOL in depth of focus is pupil size. If the pupil can constrict to a small size when making an accommodative effort (even though the eye focus muscle and lens cannot focus) the pupil gets a stimulus to constrict. Smaller pupils giver greater depth of focus. That's why its hard to predict.
re: "people with very large eyes (very nearsighted) seem to end up with better near vision after surgery than people with small eyes "
Here is a paper which gives a chart in Figure 2 of various studies testing the depth of focus of myopic eyes vs. emmetropes (good eyes) which shows that myopes have larger depth of focus:
That is in people with natural lenses, but it seems likely that it is the rest of the eye that gives the larger depth of focus and that this would be true of those with IOLs as well. Although it didn't compare farsighted people, I would suspect that they would have less depth of focus than emmetropes or myopes.
An analogy suggests why myopes with larger eye structures might have a larger depth of focus (especially if they have more light sensing cells covering that larger area). It like having a larger screen, and if there are more light sensing cells its like having with more pixels.
It is only a very small % of people who have useful near vision with a monofocal IOL set for distance, so it isn't something to count on.
Thanks Anomalychick. I wish that I had know this before my follow up appointment with the surgeon last Thursday. After a 12:45 appointment my pupils were extremely dilated at 10 pm.
At age 58 some people will feel that cataract surgery improves their near vision, some people feel that cataract surgery makes their near vision worse, and some people do not notice much of a change in either direction. Unfortunately, its difficult to tell which group you're going to be in beforehand. While cataract surgery does remove accommodation, it gives you more depth of field which basically has the same affect on near vision acuity as accommodation did. Some people get a lot of depth of field from the IOL, and some people fairly little. A few people cannot read even very large print at arms length after cataract surgery, while an occasional few can read tiny print at normal reading distance. Most people end up somewhere in between these two extremes.
While I cannot tell you which group you will be in, I can say that I suspect that people with very large eyes (very nearsighted) seem to end up with better near vision after surgery than people with small eyes (farsighted) This is simply based on a few first hand reports, I have no scientific evidence.
Now, there is something you can do that should at least give you a "worst case scenario." If you go to the eye doctor, and have them give you strong dilating drops, when you are fully dilated your accommodative muscles are paralyzed. Of course, your pupil is also 9mm wide so you have pretty much 0 depth of field. Check your near vision under different lighting while fully dilated with distance correction in place. Your near vision post cataract surgery will most likely be better, but if you happen to be exceptionally unlucky, it will be the same as under these circumstances. It won't tell you what it will be like, but it will tell you how bad it potentially could be if you draw the short straw, and at 58, you may not find it to be all that bad.
You have given me a lot of answers and prompted many questions. I have more questions on finding a specialist and will start a new thread.
You already have an excellent retina surgeon and an optometrist. I would put your efforts to seeking out the best cataract/refractive surgeon you can easily get to. I want to state what is my opinion. I would be very much suspect of the cataract surgeon recommended by your optometrist. There is a legal "kick-back" called "co-management" by which the referring optometrist receives part of the cataract surgeon's surgical fee. In return the optom provides some office visits which are usually "yes you healing fine" or "you're having problems you need a surgeon not me". The overwhelming number of optometrists do not disclose this to their patients. In our state we attempted to give "full disclosure" in which optometrists would have to tell patients they got a "kick-back" (co-management fees) in return for sending the patient to certain eye surgeons. NOTE: most surgeons do not co-manage and provide all the post operative care. The optom organizations state and local fought this with every resource they could aided by the Eye MD eye surgeons that runs these referral nets and "full disclosure" went down to defeat. You obviously have good research capabilities for find the best around. maybe even get a couple of names and see what each has to say and how comfortable you are with each. You are generally too young for Medicare but if you optom points you to a certain surgeon you might frankly ask if on his/her medicare patients if they "co-manage" (get money back from Medicare) with that cataract surgeon.
I know that I am fortunate about the acuity and also about not having headaches , eyestrain tearing etc. My correction 1/22/15 was OD -0.5 -1.00 x 085 OS -0.5 -0.5 x 102. In just over 9 months my OD increase -01.75. The January prescription was similar to my correction for most of my adult life. I have been diagnosed with nuclear sclerosis which is the type of cataract associated with increasing myopia.I am trying to figure what type of referral to lobby for when I see my primary care doctor February 8.
No it would not simulate a gain or loss of 0.50 diopter of accommodation. With ERM RE and two previous surgeries LE for ERM and macular hole your surgical results have been spectacular. A review of postings on this Eye Forum will show most people posting here don't have anything close to that good results. After two vitrectomies a cataract tends to grow reasonably fast. Also if when you were younger, say 35-45 your LE was not myopic and you have not had a scleral buckle for a retinal detachment as it is now its likely that the myopia in your LE is partially or mostly due to cataract formation. The most common types of cataract make the eye myopic (actually pseudo (false) myopic) this is called "second sight" by people and accounts for why after using reading glasses for a long time they get to be able to read without glasses.
Thanks I'll download. I downloaded Amsler grid last night.Left eye had a few very small areas of distortion but whole grid was retangular. Right eye had more distortion overall but I used readers on top of prescription glasses. I have glasses with -0.5 + some astigmatism crrecton
If I look through that on top of current prescription, would I get a sense of the .5 diopter accommodation that I would lose with an implant instead of 58 year old lens?
There is a free phone Ap that you could benefit from using its called EHB Eye Hand Book. Under the testing section it has near vision charts, amser grid plus lots of useful information
Thanks. I've seen posts on reading correction by age but I didn't know about residual focus power and I'm trying to get a sense of what I'll lose with cataract surgery, The reply from Chazas was helpful. I have read through a lot of posts from jodiej and cbct has been very helpful. I have been reading about IOL choices and think mini mono vision will work. I know I have distortion but had not thought about Amsterdam grid
First you must be looking because there is lots of material on the web about the average focus power and the needed reading glasses at different ages. This one came right up: http://hubpages.com/style/Reading-Glasses-How-to-Choose-the-Correct-Lens-Power-in-Your-Reading-Glasses Reading glasses Here's another quote: The optical power of the human eye is about 40 diopters. The eye of a normal young person can adjust an additional 20 diopters. By age 25 this accommodation (the ability to alter focus)is usually reduced to about 10 diopters and by age 50 to a mere 1 diopter. It is this diminishing capacity for adjustment, called presbyopia, that warrants reading glasses.
So by age 60 the emmetropic eye (not far or near sighted nor astimatism) will need about a +2.50 lens and residual focus power is about half a diopter.
In your case when you read you are probably using your LE more than your right. Your eyes will not focus at the same place and you're using "mono-vision" Hopefully you monitor your eyes with an Amsler Grid the amount of distortion in your LE will give you an idea how much of your "minification" is due to the uneven macular surface. As I said JodieJ posted a lot on that in the past. JCH MD
I'm very sorry for the typo Dr. Hagan. I meant to include "not" . I need to do posting on my computer not tablet.I appreciate your input very much. I created an earlier thread on aniseikonia after two vitrectomy surgeries in 2014.Left eye had macular hole and ERM. Right only ERM.The earlier post I made right after an appointment with the HMO optometrist. Yesterday's post after a follow up appointment with the retina surgeon on Thursday..Optometrist noticed start of nuclear cataracts in both eyes in spring of 2014 as well as ERMs and macular hole. I had a gas bubble in my left eye which is causing the cataract to develop more quickly. Corrected visual acuity from November appointment was right 20/20 left 20/25. left has a small defect after hole so I don't think it will ever see 20/20 again but it is close.. Almost immediately after first surgery. I noticed left image was smaller than right. Glasses prescription from November 2015 is OD -0.25 -0.75 x 90 OS -2.25 -0.50 x 110 The two diopter difference makes the left image even smaller. Retina surgeon asked if I wanted to see a cataract surgeon because that would eliminate the image reduction from glasses.I told him that I was in no hurry for more surgery. Even though I told both eye doctors my biggest issue was size difference and accompanying double vision, neither put aniseikonia on my list of issues. I have an appointment with my primary care doctor on February 8 and I hope to get some testing done. None of the doctors has addressed it at all in many appointments in 20 months. I have read though your journal entries and many posts on Medhelp and other sites on both aniseikonia and cataracts but haven't seen information on how much focusing power people average at particular ages. It is one more factor in the decision. I don't wear glasses that much -just for distance. They are single vision and I can see to read and use computer without. This may be part of the reason that the double vision is a distraction rather than causing headaches, eye strain etc but I have reduced driving.
You should NOT rush into surgery
Thanks. It sounds like I should rush into surgery
Please read this very very carefully it will save you a lot of grief later on: http://www.medhelp.org/user_journals/show/1648102/Consider-ALL-the-Options-Before-Your-Cataract-Surgery-Working-Through-Whats-Best-For-You Also
review the many discussions about post cataract surgery uncorrected refractive error targets.
You might. I have a single focus IOL in one eye, and the other eye has a -9.0 single focus contact lens. I can see clearly beyond about 4-5 feet in the eye with the contact lens, the clear zone starts considerably further out in the eye with the IOL.