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Avatar universal

wanting to stay nearsighted after cataract surgery

I'm 41 and have posterior subcapsular cataracts (currently with much more severe symptoms in one eye than the other).  I've been highly myopic all my life (about -9) and I like wearing glasses; being able to get by with thinner glasses than I currently use for distance vision would suit me just fine.  

I find glare/halos/etc very distracting (so having posterior subcapsular cataracts is a joy, let me tell you), and it bothers me a lot when the vision in one eye is different from the other.  So neither multifocal IOLs nor monovision sound appealing to me.  

I do a lot of reading and computer work, so I'd be very happy with vision optimized for that.  But I've seen very little discussion of the difference between vision at reading distance and at computer distance.  I had a consultation with a surgeon recently, but he glossed over that part rather quickly, only noting that I'd have to pick one or the other.  My inclination is computer distance, since seeing well at arm's-length or slightly under is useful in a lot of situations.  Do people ever end up with vision set for a near/middle point that works acceptably for both reading books and seeing computer screens?  I know that choosing the IOL power is not as an exact science as one might like, and results vary, so there's no point in wringing my hands over whether I'd like to see perfectly at 14" or 18".  But I'm barely starting to get symptoms of presbyopia, so I don't fully understand what it's like to be focused at one point.  Is there any degree of range to this (like "I can see okay at this distance, plus or minus a few inches")?  I've searched the internet for experiences of people who preferred to stay myopic after surgery, and they've been useful, but I'd love more input.  
4 Responses
Avatar universal
In your situation I would probably aim for -1.5D in both eyes, which gives best focus at 2/3m, or slightly over 2 feet. If you tend to hold things close up, you could even have -1.5D in one eye and -1.75D in the other, and the monovision would be so slight that you wouldn't notice the difference between the 2 eyes.

How much depth of focus you get is variable, depending on the degree of astigmatism and other optical aberrations. Another big factor is the lighting, so better lighting post op will give you better depth of focus.

High myopes also tend to have less predictable post-operative refractions. If a surgeon is unfamiliar with operating on long axial length eyes, they tend to give the patient hyperopic outcomes. Do ask your surgeon if they compensate in their calculations for people like you.
Avatar universal
You could consider an accommodating lens like the Crystalens , where you might get a larger range of vision, since the major risk with those is simply that they don't accommodate. Unfortunately there are some added risks, such as Z-syndrome, but I think those may be mostly fixed in the most recent version, but I'm not positive since I hadn't researched it.

(I decided to instead go   out of the country for a lens not FDA approved yet, which I assume most people won't do, so I'll just suggest looking at the threads on the Symfony if that is an option).

re: "I'm barely starting to get symptoms of presbyopia, so I don't fully understand what it's like to be focused at one point"

Fortunately you don't focus at *exactly* one distance, eyes with monofocals do have some "depth of focus" so they can see a bit in closer than the distance they are set for. (and not all monofocals are created equal, as I'll get to). How well you can see closer in depends on the depth of focus you have with a particular lens, which you'll have to search for. There studies for most lenses out there that indicate how your vision will vary depending on the distance. They show the information in what is called a defocus curve, which indicates for instance that you might see 20/20 at distance with a lens but then 20/40 at 40 centimeters. This article explains:

http://www.lasikofboston.com/pdfs/Dissecting_the_mean_defocus_curve.pdf
"Simply put, a defocus curve provides an indication of the level of vision a patient can expect at various distances, [...] For example testing distance acuity through a -2.00D lens is equivalent to testing the patient's vision with a chart at 50cm. "

The diopter measure in a defocus chart is an indication of distance, with 0D being at infinity, -1 diopter being 1 meter, and as that quote indicates -2D corresponds to 50cm. This page gives a chart of diopters versus distance, and gives the conversion formula:

https://www.slackbooks.com/excerpts/67956_3.pdf

Unfortunately many charts refer to visual acuity in units of  logMar instead of the 20/X units people are used to, but there are conversion charts on the net, as well as charts that give an indication of what print size you can read with a certain visual acuity (its surprising that most only requires 20/50 or 20/60 even).

Those defocus graphs   usually assume people are going to be focused at infinity, but if you choose to be focused in closer you can just shift the chart. For instance consider the case of choosing   to be focused at -1D (1 meter). If a curve says that at 0D you'd be 20/20 and  at -3D (33.3 cm) you would be 20/40, then you can add -1 diopter to those. So instead of being 20/20 at  infinity, you   would be 20/20 at   -1D (1 meter)  and at -4D (25 cm)  your vision would be 20/40.

There have been a number of studies on lesser amounts of monovision which don't impact binocular vision, steroacuity, much if at all. Apparently people that can't tolerate the usual difference between the eyes in full  monovision have no trouble with this. . Its variously referred to as micro-monovision, mini-monovision, or "modest monovision" depending on the amount, which gives at least some more near vision. Unfortunately it is harder to predict the IOL power in high myopes so they may not succeed in pulling off a small difference like that, some surgeon bundle in laser enhancement with the surgery so you can get a touchup if they don't hit the mark.  

  The amount of "depth of focus" for a monofocal varies with the lens (and the amount of monovision, if any). There is for instance a new FDA-approved Hoya lens,  the iSert 751 Gemetric,  which apparently adds perhaps an extra 1 diopter compared to typical monofocals. It has been researched by Dr. Graham Barrett (if you see his name on something to do with an "extended depth of focus" lens then by default it appears to be that lens even if it doesn't give the brand&model). He has also studied "modest monovision" with it:

http://eyeworld.org/article.php?sid=6565
"A new clinical study on the extended depth of focus (EDF) IOL began in February, with results showing that a patient gains 1-2 lines of focus with the lens, Prof. Barrett said. The new IOL provides an additional 1 D depth of focus compared to a standard negative aspheric monofocal IOL, but still meets the ANSI and ISO standards for optical quality required for a monofocal IOL, he said. "

In this study he compared setting the lens for distance ("emmetropic", no refractive error) with modest monovision:

https://ascrs.confex.com/ascrs/14am/webprogram/Paper6552.html
"Extended Depth of Focus IOL and Modest Monovision
LogMAR unaided binocular visual acuities for distance, intermediate and near were -0.02, 0.06 and 0.3 in the emmetropic group (N=24) and -0.04, -0.04 and 0.2 in the monovision group (N=21), (p= 0.12, 0.001 and 0.02, respectively) "

The eyes without monovision for near were logMar 0.3=20/40, with modest monovision they were logMar 0.2 = 20/32, which is useful for many things.

http://digital.eyeworldap.org/i/203136/34
"This provides about 1 D additional depth of focus"

http://crstodayeurope.com/2014/12/trends-in-refractive-surgery-and-in-presbyopia-correction
"Few visual disturbances are expected with the Symfony or the iSert 751 Gemetric lens (Hoya). Graham D. Barrett, MD, FRACO, reported better image quality with the Gemetric IOL than with negative defocus.3 If emmetropia is targeted in one eye and myopic defocus in the other, the overlap of defocus in the 20/20 to 20/40 range creates a zone of blended vision that avoids the disadvantages of traditional monovision."

Here is a video of Dr. Barrett talking about his work:

  http://ewreplay.org/node/783?v=3510637608001

and more of his work   on modest monovision:

http://escrs.org/publications/eurotimes/12May/modest-monovision.pdf

It appears the Hoya was approved for use in the US last summer:

http://www.massdevice.com/news/medtech-approvals-fda-releases-june-2014-pmas?page=11
"The U.S. Food & Drug Administration releases a list of pre-market approvals granted in June 2014.
The device, as modified, will be marketed under the trade name iSert® Gemetric™ Model 751 and is indicated for implantation after extracapsular cataract extraction or phacoemulsification of cataracts in adults. "
  
I'll note that an expert on IOL power calculations who has a page on the difficulties that high myopes face:
http://www.doctor-hill.com/iol-main/extreme_axial_myopia.htm

apparently will provide consults to other doctors on IOL power, which I hadn't known before I got my surgery.
Avatar universal
It depends of course on what near hobbies or activities you might have what is most useful. One important thing to remember is that results will vary with each person. Different people's eyes have different natural depths of focus, some small lucky minority can even manage to read with monofocals set for distance. The results of studies are merely averages.

Here is an example defocus curve for the Tecnis monofocal (comparing it to the Symfony):

http://www.tecnisiol.com/eu/tecnis-symfony-iol/img/technology-defocus-curve.jpg

which shows a range of about 1.5 diopters where you still have at least 20/40 (fairly usable) vision. So if for instance you were set for -1D, to focus best at 1 meter, then you'd still have 20/40 vision at -2.5D = 40 centimeters which is often the typical "near" vision measurement. That would encompass typical computer&smartphone distance, as well as many "arms length" to somewhat close household activities (remember that looking in a  mirror is the distance to the mirror and back). If you went for -0.5D that would give you focus at 2 meters which then encompasses much social distance, people around a table, up through -2D=50 centimeters or a bit further out reading distance. Common computer distances would be in between, at -1.25 to -1.5D or so.

The reports I'd seen indicate the Hoya doesn't give   as much depth of focus as the Symfony, even though that graph shows an added 1D of depth of focus just like the Hoya claims. It had sounded like the Symfony often gives reading vision without monovision (I get 20/25 at near) but that monovision was needed with the Hoya to likely get it. Perhaps the Symfony is a bit more than 1D and the Hoya a bit less and they just round to the same.

(FYI for those who hadn't noticed, for those unused to metric distances, google will do unit conversions, e.g. "50 cm in inches" and it'll do it as you type in the search box in Firefox, and the address bar in Chrome).
Avatar universal
This is strange, I'm waiting for more info but I just got a report that although the Hoya lens was approved by the FDA, they may not be commercializing it here. That seems to make little sense from a business perspective, I just assumed that after going to the trouble of getting  FDA approval any rational company would be selling an improved monofocal. It would explain why there hasn't been more written about it online though, I'll add a comment if I get more information.  I don't know if there is some glitch with the lens we haven't heard of, if they are getting out of the IOL biz, or if its merely that not all businesses are competent.
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