Pros & Cons of -0.25 vs. +0.25

[Turbo3800]

I am having my restor explanted for an aspheric monofocal.  The power of iol's come in .5 increments meaning if you get the correct iol you may still be off by as much as 0.25.  If you have to choose between an expected +0.25 vs. -0.25 what are all the pros and cons of each?

0-3 ft - No doubt -.25 is better, no discussion needed
3-6 ft. - again -.25 is the better choice
6 -20 ft - are the lens now fairly equal?  Does it really matter?
over 20 ft - I would guess the +0.25 is better but since they are off plano the same maybe not

As you age, don't your eyes slowly go to the plus side for most people.  If so, is this a consideration of choosing -0.25 to a +0.25?

Discussion would be greatly appreciated.  I have tried monovison with contacts and do not like it.  I am active outside, enjoy tennis, ping pong, watching tv and am not sure which power will best suit my needs.  For 6 ft and closer I expect to wear glasses.

Thanks,

Greg

[Turbo3800]

Well, no complications from the surgery.  They blocked my eye so I have really bad double vision right now and all distances are somewhat blurry so too early to tell.  The Dr said before surgery that Alcon stated the measurements stated I should use a 17.  The Dr said his experience showed that we should go with a 16.  I had a 15.5D in the restor prior to surgery  and since the acrysof has a different A constant the fact that I was +.12 before showed that I should be about a -.1 with the acrysof 16.  I agreed the 16 made more sense regardless of what the alcon tech said.  Tough decision.  To me, the measurement guess just seemed way off.  I hope so.  Anyway, sorry if this is too technical for some but I figure Jodie wants the details...haha.  

[JodieJ]

Best wishes for a great outcome!  Let us know how it goes.

[Turbo3800]

Well I will get my restor explanted tomorrow morning.  I chose the acrysof since it calculates out to a -0.1 compared to the technis which was a -0.32.  Both have uv protection but supposedly the acrysof has better protection for macular degeneration (not sure I believe the hype).  This is the 3rd (and last I hope) surgery on this eye so pray for me.  It is scary knowing this is the 3rd one but I just can't stand the restor anymore.  I will post my results for those interested.

[JodieJ]

CSBDR has given you excellent advice.  It's impossible to say which IOL (AcrySof vs. Tecnis) will get you closer to plano.  Both IOLs have excellent UV protection.  Your best bet might be let your surgeon's experience dictate your choice--more experience with a particular IOL can increase the odds of coming closer to the targeted refraction.

[CSBDR]

Each IOL has a specific "constant" associated with it.  This constant is then used in various IOL formulas to best PREDICT what power is needed for a specific refractive outcome.  There are so many variables that dictate the actual refractive outcome, with the main ones being corneal power, axial length, and the least predictable element of ELP (estimated lens position, meaning how far into the eye the IOL sits).  As Dr. Hagan mentioned, with the best of measurements one cannot expect to be within a quarter diopter more than about 50-75% of the time, yet alone repeat it twice in the same eye.  Your case makes calculation even less predictable.  A new corneal incision will change the keratometry value, but going through the old incision may cause more wound stretch and will cause swelling which can change the keratometry value.  There are also the issues of capsulotomy size, more inflammation causing fibrous reaction in the capsule, macular edema risk, etc.

Tecnis IOLs have full UV protection, they just don't have a blue-light filter, which is very controversial in ophthalmology anyway.

For your own mental wellbeing, temper your expectations and hope for a pleasant "surprise"

[Turbo3800]

Thanks again Jodi.  Right now with the restor I am +0.25 with a 15.5D.  If I replace it with the acrysof IQ, my understanding is that they are not at the same power as the restor.  I think the Dr. said you need more power with the acrysof to get the same results.  I am not sure how much more but figure there is a calculation that they should be able to predict.  If the power distance is small, I would guess I will be getting a 15.5D in the acrysof which should get my closest to plano (should be closer than 16).  However, the Dr can also implant the technis aspheric as well.  I am wondering if you again can calculate if this will get my closer to plano or slightly myopic.  The downside is that the technis has no uv protection but I am thinking the two lens choices are so close that the one that should get my closest to plano or slightly near sighted should be my best choice.  

Considering that measurement can only be so accurate, I believe basing the decision off my restor result is the best way to go.  Any thoughts?

[JodieJ]

Here's a nonprofessional response:  -.25 is definitely the better option because it would give you better near/intermediate vision.  Distance vision would be about the same with either option, even beyond 20 feet.

Having both eyes plano would make everything within arm's length blurry for most people.  If everything within 6 feet is blurry, you are farsighted.

Some time around age 40, people begin to lose their ability to focus up close (presbyopia) and begin to need glasses for reading.  This happens regardless of whether they are nearsighted, farsighted, or have had perfect vision.

As Dr. Hagan suggested, making IOL power predictions is not an exact science.  Most people end up within .5 diopters of their target.  So if the target is plano, they will likely be between +.5D and -.5D.  Some factors which make the predictions less reliable (thereby increasing the range of likely outcomes) are severe nearsightedness/farsightedness, significant astigmatism, and previous laser vision correction.  The "correct" IOL power for you is not the same for all IOL brands/models.  I don't know whether having an explant would influence the power prediction.

[Turbo3800]

I have searched and have not found the info I needed and thus asked the question.

I understand iol's come in .5 increments as I noted in my post which is the reason for my question.  My concern is the distances I noted as well as if how my vision could change in the future.

Thanks,

Greg

[John C Hagan III, MD, FACS, FAAO]

Use the search feature and archives to read the numerous discussions of picking IOL power.

One thing you should know. The IOL forumla even under the best of circumstances are only accurate within plus/minus 0.50 diopter to diopter so you cannot "SET' the power with absolute certainity.

JCH MD