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Lasik, lens replacement, et cetera

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#1 macdonjh

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Posted 28 June 2019 - 12:40 PM

This all started in the Refractors forum (https://www.cloudyni...s/#entry9463348).  I wanted to comment, but didn't want to hijack poor starcruiser's thread, so here's a new post.

 

Copied from TOMDEY's posts:

 

Hi, starcruiser; Great question and ostensible concern!

 

We DO have significant, traditional Longitudinal Chromatic Aberration. My recollection is that it's about 1/6 Diopter, "undercorrected".

 

OK... OK... I just computed it from 1st principles, assuming that the human eye has a 1-inch focal length and is made of water and I get 0.29 Diopter (@450-650nm)... reasonably in the ballpark of my recollection... especially considering that there is more stuff in there and different dimensions. Optometrists generally refract eyes to about a quarter of a diopter accuracy... but a really scrupulous patient (like me) can discriminate differences of about a tenth of a diopter. So, the chromatic of our eye is just enough to be pretty annoying... depending on how picky you are.

 

Our eyes also have traditional (Seidel lateral cubic) Spherical Aberration. And that is quite substantial for dilated pupil. Lens Implants and/or Lasik/PRK actually correct the ~natural~ spherical aberration of the human eye! I had those surgeries done and actually do enjoy the hyper-acuity consequent of those improvements. 20/12.5 each and both eyes... even with dilated pupils. And that makes it really nice for enjoying things like star clusters. I just don't need as much magnification as my companions, to see all the detail. Worth considering, as an additional motivation to get one's eyes done. I've commented before that when I look out at the yard (post improvements)... that every blade of grass, tree twig, etc. looks razor sharp. I'm not kidding --- the improvement is that dramatic!    Tom

 

Hi, Kerry! Ophthalmologist Surgeons now offer ~True Astronomical Infinity~ correction, both eyes, dark-adapted open pupils, rather than the usual default of closer in, constricted pupils, not quite able to focus out to the stars. Our local guy here, at the teaching hospital, includes that option right in his marketing literature! Keep in mind that you entirely lose focus accommodation when your old cloudy yellow bio-lenses are replaced with pristine clear prosthetics. The implants also correct your astigmatism and even the ~natural~ spherical aberration of the human eye! Your vision will become laser sharp day and night true infinity. If there is any small (typically tiny) residual focus and/or astig remaining... PRK and/or very mild "no line" glasses will take care of that. My final correction, after the surgeries and settling-in time... came out perfect 20/12.5 Dark Adapted in one eye and the other also measures 20/12.5, but has tiny remaining astigmatism... tiny. So the stars look like miniscule bright dots.

I have progressive eyeglass lenses so I can read thru the bottoms and see infinity through the tops... plus that little astig correction on one side. With the glasses off, I can't read! Getting one eye far and one close is a pretty debilitating compromise. Even worse are surgeries that focus near with one zone of the lens and far with the other --- so you can resolve both but never again see anything very well focused! My surgeon strongly suggests against those... will only do that if the patient demands them and signs off on vision quality.

Regarding congenital/progressive nature of eye lens degradation. We all have a combination. The congenital component, you can be lucky or unfortunate, but never immune... we all have human genes; progressive, we all suffer that too. A lot of sun can accelerate the degradation, but it's as inexorable as wrinkly skin. And... just like wrinkly skin... gets quite noticeable around age thirty-five. That from my optometrist... he said he looks in there and can tell a person's age quite accurately... the eyes' interior don't lie! He then commented that people would opt for the surgeries at 35, if cost were no object; I got mine done at 65 and WOW! But, optometrists are not going to tell you that unless you press the issue. Just like your Primary Care doctor won't tell you that your skin is getting wrinkly. And friends won't tell a 35-year-old that she looks 35... they'll politely "guess" twenty.

Most of us (even astronomers) are very tomophobic... throwback to mom cautioning, "Don't poke your eye out!" That puts us in a state of denial, "Oh, my eyes are still perfect... Ehhh... perfect!" Yeah... and I'm 35, going on 72!

Results may vary.

 

I can second TOMDEY's comments about Lasik.  I had Lasik before I was thirty (the date excapes me).  Unfortunately, sometime in my 40s I "outgrew" Lasik (OK, my eyes continued to evolve and my prescription changed) and my astigmatism came back.  I approached the ophthalmologist who performed my Lasik something like sixteen years previously about doing it again.  He didn't recommend two Lasik procedures, the second attempt doesn't heal properly in something like 1 out of 5 procedures.  Those odds were too poor for me.  He then did an LRI (limbal relaxing incision), a single cut in the cornea, similar to radial keratotomy.  I enjoyed super-human clarity like TOMDEY describes for about three days.  Then my cornea healed and scarred and I went back to what I had prior to the LRI.  Too bad for me.  My ophthalmologist says I need PRK (kind of like Lasik without the "flap"), but with a laser that isn't FDA approved yet.  So I either wait, or I take a trip to his clinic in Monterrey, Mexico.  Sigh.


Edited by macdonjh, 28 June 2019 - 12:44 PM.

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#2 Eddgie

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Posted 28 June 2019 - 07:23 PM

Not every condition can be corrected with Lasik.

 

I have had six procedures on my right eye in the last two years.  One was to remove a cataract, and one was to buff my cornea for a condition called Map-Dot-Fingerprint dystrophy.  The next four were to correct for near or far sightedness.

 

The specific operations I had were photorefractive keratectomy or PRK.  Sadly, in my case, my eye did not respond in the way the typical eye responds, and the measurements plugged into the wavefront laser would overshoot.  This means that while most people can get a good result, it is not at all a sure thing and some report much less than complete success. So, while most people get very satisfying to excellent result, there is no guarantee.

 

The doctor will tell you if you can have Lasik or if you need a PRK.  Lasik recovery is very quick (a couple of days, with almost immediate improvement).   PRK Is a much different story, with complete vision stability taking as much as several months.


Edited by Eddgie, 28 June 2019 - 07:24 PM.


#3 denny-o

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Posted 29 June 2019 - 07:18 AM

Something I have long reiterated is  - 'just because we can does not mean we should.' Despite that, I am close to pulling the trigger on lens replacement due to cataract issues causing double vision (I can no longer use a visual scope for more than just a casual look) I also have astigmatism but I am not keen on having anyone whittle on my corneas.

We are still working the fields trying to salvage something from a miserable growing year, hoping to at least break even. Perhaps in a month I can find the time to be laid up for a bit. We shall see what I decide.



#4 Eddgie

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Posted 29 June 2019 - 07:36 AM

Something I have long reiterated is  - 'just because we can does not mean we should.' Despite that, I am close to pulling the trigger on lens replacement due to cataract issues causing double vision (I can no longer use a visual scope for more than just a casual look) I also have astigmatism but I am not keen on having anyone whittle on my corneas.

We are still working the fields trying to salvage something from a miserable growing year, hoping to at least break even. Perhaps in a month I can find the time to be laid up for a bit. We shall see what I decide.

Recovery from cataract is very fast.   They operate on you and usually bandage your eye no more than one day (though the last time I had this surgery, they did not even do that, but I could not see well out of the eye for about a day).  You sleep with an eye guard on for about 4 or 5 days as I recall, but after the first day, you are seeing well.  No lifting or bending below the waist for about a week.  Lots of drops.   That's about it.  Far easier than a PRK, where it takes weeks to months to be able to have your full vision correction. 

 

I don't know exactly where the line is for Lasik vs PRK, but a lot of people that I see in my doctor's office are getting PRK.



#5 macdonjh

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Posted 29 June 2019 - 07:58 AM

denny-o, the two or three people I know who have had cataract surgery all said they wish they'd done it sooner.  It seems to be one of the lower-risk surgeries there is.  Apparently we're pretty good at it.

 

eddgie, my ophthalmologist said the same thing to me about the recovery time for PRK.  More than twenty years ago I was told that Lasik was a good option for me, recovery time was short and risk was low.  I didn't really need to hear more than that.  This time around he says I'm not a candidate for Lasik and recommends PRK if I want to get my vision corrected again.  I think the surgeons may have more options with what they can do with PRK, since there's no flap covering up the changes they make.  But then, I haven't asked.

 

I just wish that LRI had worked.  I had super-extra sharp vision for three glorious days.  Truth to tell, my left eye is sharper than my right eye, but not enough that I think LRI is the right procedure.


Edited by macdonjh, 29 June 2019 - 07:59 AM.


#6 Eddgie

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Posted 29 June 2019 - 08:29 PM

denny-o, the two or three people I know who have had cataract surgery all said they wish they'd done it sooner.  It seems to be one of the lower-risk surgeries there is.  Apparently we're pretty good at it.

 

eddgie, my ophthalmologist said the same thing to me about the recovery time for PRK.  More than twenty years ago I was told that Lasik was a good option for me, recovery time was short and risk was low.  I didn't really need to hear more than that.  This time around he says I'm not a candidate for Lasik and recommends PRK if I want to get my vision corrected again.  I think the surgeons may have more options with what they can do with PRK, since there's no flap covering up the changes they make.  But then, I haven't asked.

 

I just wish that LRI had worked.  I had super-extra sharp vision for three glorious days.  Truth to tell, my left eye is sharper than my right eye, but not enough that I think LRI is the right procedure.

Yes, it is not just that they have more options, but apparently Lasik simply can't do some of the corrections that PRK can do.  There are also wavefront lasers that can contour the sphere of the eye.  While Lasik can change the sphere (near or far sighted) if there are irregularities in the sphere (like a small hill or bump) a PRK using a wavefront laser can in theory remove the high spot and return the eye to spherical shape. 

 

The worst parts are these...  

 

For PRK, the epithelia over the cornea is removed, then the laser is used to do the surgery.  After, a zero power contact (called a bandage contact) is put on the eye to protect it while the epithelial layer grows enough to re-cover the cornea.   This takes about 5 days, but this is just to fill in from the outside.  It takes another several weeks for the cornea to grow back to its full thickness and during this time, the vision continues to improve.

 

The worst part is that for the first 3 or 4 days, the eye can be quite uncomfortables.  and if the contact comes off in your sleep, it can be horribly painful.  My advice is that if you have this done, try to get them to do it on a Monday so that if there is a problem during the week, you can get into see someone. I lost a contact on my 4 day and it was a weekend, and I suffered badly for about 3 hours until I could get a doctor to come in and put in another contact.   The pain was extreme.   This was though only once out of the four surgeries I had. 




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