Vision without an IOL or natural lens

[AndySKane]

I had right cataract surgery in 2003, after retinal detachment and a vitrectory.  The lens capsule as come loose and I have repair surgery scheduled for next Tuesday, either scleral tunnel fixation or sewing the lens to the iris, depending on what the surgeon find.  

Here's my question, which I plan to ask my opthalmologist this afternoon.  I was quite nearsighted with the original corrective rx of -11.50.  My IOL is 5.  I'm wondering what the optics would be if I had the IOL removed and not reattached.  Would a simple contact lens of +3 or 4 be sufficient to focus for distance?  I ask this because If I tilt my head I can see around the IOL (I think that is what I am doing) and with a + 3 lens can see quite well in the distance.  I would want to do what ever surgery would be the least traumatic for the eye and give less complications in the long run.  Has anyone done this?

[AndySKane]

I had the scleral tunnel IOL fixation surgery yesterday.  I opted to have the loose lens reattached by fixing it to the sclera and the capsule removed.  Since it had been in my eye for 12 years the surgeon was not sure if the existing IOL could be reused and had two backups in case not.  It was reused and the surgery was successful.  She also did not know if my sclera was thick enough for the tunneling procedure until she went in.  It was.  The back up was to sew it to the iris or remove it entirely, at her discretion.  My vision is blurry now but she expects it to be as good as before after swelling goes down.  She spent a lot of time cleaning scar tissue from previous surgeries and other cleanup around the old lens capsule.  I'm using Ofloxacin and Prednisolone drops for inflammation and for antibiotic.  Total operation time was over two hours.

So far so good, I'm optimistic.  Bandages came off today.  My next doctor visit is next Thursday.  I am very pleased with the effort the surgeon put in.

[JohnHaganMD]

=

[SoftwareDeveloper]

Since you have a nominal 20/20 vision after the cataract surgeries it suggests the IOLs were on the mark. The required power of a lens depends on the how far out it is, so that e.g.  a contact lens prescription is different from a glasses prescription since the lenses are further out. To compare the power of an IOL with the power of a contact lens to give the equivalent result (were the IOL removed) would require knowing the exact position of the IOL, which varies by person. However in this case you are just trying to get a rough idea.

One way to do that is to look at what IOL Master results say, they give the estimates for various formulas as to what the resulting refraction at the spectacle plane would be with a given power of IOL. Looking at mine, I see that a rough estimate is that a change of 1.5 diopters at the IOL plane yields about a 1 diopter change at the spectacle plane. That matches comments I've seen regarding the adds for multifocal IOLs, where the add at the spectacle plane seems to be estimated to be about 2/3rds of the add given at the IOL plane.  That suggests since your IOL is 5 that 2/3rds of that would be a 10/3= 3.33D power difference at the spectacle plane if the IOL were removed.

  If you do a google search of   "iolmaster printout" and check some of the resulting images, the 2/3rds estimate seems to be close enough.

If you had IOL Master results for your eyes you could see what they say. Alternatively if you have the measurements from an IOL Master (or the equivalent), I recall running into IOL power calculator sites online before (I don't remember links offhand). Usually the idea is to tell it the desired refraction, and it'll show the lens powers that are about right. However you could keep changing the desired refraction until the lens power that comes up is 0D.

As to the medical issue of whether an IOL is better left in, or whether  having an IOL impacts optical quality, I hadn't checked on that.

[JohnHaganMD]

=

[AndySKane]

Thanks for the info.  Your rough calculation approximates what I found.  This morning the IOL capsule moved further where straight ahead I no longer see it and can try on glasses without tilting.  With a +3 over the right eye and no lens over the left eye I can see fairly well into the distance with both eyes focused, but near vision on the right is very poor and would need more corrective RX.

This upcoming surgery is much scarier than the others I have had and it is good to know that I have a fallback in case the scleral tunneling or iris fixation doesn't work.  I'm laying low till Tuesday now because I really don't want to have the capsule totally come loose and float around.

[JohnHaganMD]

=

[AndySKane]

Thanks for your response by I guess I didn’t make myself clear.  Let me try again.
I was nearsighted in both eyes with these final prescriptions before cataract surgery.

Right eye:
Sphere: -11.50
Cylinder: -2.75
Axis: 18

Left eye:
Sphere: -12.25
Cylinder: -1.50
Axis: 163.0

I had cataract surgery in both eyes with these intraocular lenses put in.

Right eye: 5
Left eye: 6.5

From my understanding, nearsightedness occurs when the natural eye focus point is before the
retina.  In eyes most of the light refraction is done by the cornea and secondary focus is
done by the lens.  When the correct refraction power for the IOL is selected, a measurement
and calculation is done based on the refraction of the cornea and any other ancillary
refraction of other remaining parts of the eye.

What I was wondering is if my right eye required an IOL power of 5, to give me nominal 20/20
vision, what would the power of a contact lens be needed to give me the same correction if
the IOL was removed?  This seems to me to be a mathematical equation for someone with knowledge
of eye optics and the internal distances to account for the distance difference between a
contact lens and IOL.  There is no vitreous in this eye, any residual around the capsule will
be removed.  If I tilt my head and look around the loose IOL to the distance I seem to see
quite clear and focused with a +3 glasses on.   A +3 is not particularly thick when I
had -11.50 and -11.25 most of my life.  This is the basis of my inquiry.

Yesterday I asked my ophthalmologist, who is also the retina surgeon, about this.   She said it
was interesting and that if the lens capsule completely detaches I could then see how well the
glasses work to correct.  Since I really don’t want it to come loose I’m laying low till
Tuesday when the surgery is to be done.  She also told me that to remove the existing IOL would
require a fairly large incision and would not be preferred.  As to long term durability, because
of the cleanup required around the capsule all final fixes, including no lens, would have about
the same durability and complication probabilities.  She also said that having a lens in would
facilitate any future laser surgery, if needed.  

I decided not to pursue not having an IOL but am still curious about the optic math involved.
So, based on this, what power contact lens would be need?

[JohnHaganMD]

There may be a formula that might be constructed but I'm not aware of any.  It's not at all a common situation and not like having multiple formulas for determine IOL power.  
Also your statement is incorrect that and IOL power of 5 is to give you 20/20 vision.  The IOL formula say absolutely nothing about the vision with an IOL it only calculates the hoped for post operative refractive error.  For example one person may have a residual refractive error of 0.00 (plano) and have 20/200 vision if they have macular degeneration or history of retinal detachment while another with post op error of -1.50 may see 20/20 with glasses and be able to read without glasses.

[AndySKane]

I don't want to belabor the point but I said a nominal 20/20 vision after the IOL of 5.  By this I mean for distance I could see well without any further corrective aid but needed reading glasses for close up sight.   I understand that the upfront measurement is not 100% predictive but in my case it worked out well.  I had asked for the best correction to see in the distance.   Again, thanks for your help.

[JohnHaganMD]

What is your POST cataract surgery glasses RX since you've had surgery on both eyes I'm assuming no one would leave you that myopic.

[AndySKane]

My post cataract surgery RX is nothing needed for distance and for close up the RX is +1.50 right and +1.25 left, which I do with reading glasses.  I have been very happy with this setup but now it will be changing with the loose IOL capsule.

[JohnHaganMD]

No it doesn't work that way. You would need your eye remeasured and adjustments made for it not being in the same exact place as usual for uncomplicated cataract/IOL surgery. Even if you were left with +3 refractive error your glasses would very thick, your vision without glasses bad, you would need progressive no line bifocals and you don't way what your RX is in the other eye. chances are its myopic also and would not match up with a hyperopic refractive error.

[AndySKane]

Interesting about the hyperoptic refractive error.  I had cataract surgery in my right eye in 2003 and for 11 years I wore a -10.00 contact lens in my left eye and none in my right eye without any negative effects.