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Laurie
medicine forum Guru Wannabe
Joined: 07 May 2005
Posts: 172
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 Posted: Fri May 20, 2005 7:48 pm Post subject:
Re: A little survey about halo in LASIK
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| Quote: | I admit to have trouble following your "other type of distortion." Do
you mean a non-homogeneous area of ablation, edema, or
something else?
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I mean to continue saying what I said on that message from yesterday which
begins "Ok.". There I put my speculation about the causes. If I wasn't
clear, there were mistakes or it is difficult to understand what I wrote,
I'll be glad to discuss about it. Basically what I called "second type of
distortion" is caused by light being scattered because of the changes
between the surface of the stroma and the epithelium, where cellular
structure is violated (and cracks etc. easily visible to the ultrasound are
present as well).
| Quote: | Foolproof, you say? Why do calibrations, then?
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I don't know at all how they calibrate it. If it's human calibrated at
micron level (as opposed to rough positioning), I'm surprised. At least I
suppose the real-time eye tracking has to be very highly effective and
accurate. I accidentally turned my eye completely at the wrong direction in
the middle of lasering, but that eye is actually the better one now.
| Quote: | If it happened the way it was supposed to happen, then you
can make a case for a design flaw.
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I would imagine that with today's generation equipment it is not a problem
to make very accurate lasering. And that when unpredicted result occurs,
it's rarely because of inaccurate lasering but because of the unpredictable
nature of the stuff piled back on the stroma (and the space between the
stuff and the ablated stroma).
| Quote: | I think you might have missed my point, which is that there is lack of
consistency not only in the devices used to measure pupil size, but
also in the conditions used to measure pupil size.
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Yes, it is possible. But I find the task quite simple compared to many other
things humans are capable of (the required accuracy is just 0.01mm level
which shouldn't be that difficult). Let's analyse it at practical level: if
the measurement is made always horizontally and the equipment has 0.1mm
accuracy (including the deviation caused by different interpretation) and
the sealed room is very dark, is there much that can go wrong?
If the situation is something like so that the devices have 0.5mm accuracy
(or huge differencies among different models) and the room illumination is
sometimes dark and sometimes lots of light is coming in through the
windows - well, then something is horribly wrong. What is the purpose of
measuring pupil size if it's not confirmed that the method and conditions
are accurate? |
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Steve
medicine forum addict
Joined: 16 May 2005
Posts: 59
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| Posted: Sat May 21, 2005 9:24 am Post subject:
Re: A little survey about halo in LASIK
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| Quote: | 1. How long since you had the (first) surgery?
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3 years
| Quote: | 2. Do you see distortion of any kind, in daylight or in dark? If you answer
No, you can stop the survey here, but add a comment about your vision (be
critical, show that you do pay attention to visual quality).
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Yes.
| Quote: | 3. Do you see disturbing starburst around small/distant lamps at dark?
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At night, I see "slight" starbursts around small/distant lamps. It is
almost unnoticeable, but I am very "picky" about my vision.
| Quote: | 4. Do you see disturbing halos around bigger/closer lamps at dark?
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Not any more, although I did for the first 18-24 months after
surgery.
| Quote: | 5. Does the starburst/halo size around lamps change when the pupil size
changes? If yes, does the halo reduce to zero or practically almost zero
(you can test this for example by looking out a window at night and then
constricting the pupils by the use light, eg. flash light)?
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Yes and yes.
| Quote: | 6. Has your starburst/halo size or brightness changed after surgery? If yes,
please tell how did you measure this (looking at the same lamps month after
month from the same spot can be a good test).
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I had changes all along, but the most dramatic changes were during the
18-24 month period after surgery. I "measured" this by looking at the
same street lights in my neighborhood from month to month.
| Quote: | 7. Do you see a less blurred image if you look through "finger binoculars"?
Roll your index fingers and look through the small holes formed. Look at
something in room illumination with high contrast, for example a black
poster with white text or a white object on black background.
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Yes, no distortion at all.
| Quote: | 8. Do you have difficulties recognizing faces if the person is standing in
front of a bright window -- or do you see everything more or less foggy in
room illumination?
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No, although these were issue during the first 6 months or so after
surgery.
| Quote: |
9. Your happiness about the result (0-100%), where
- 100% = aquity is 20/20 or better, there are no side-effects
and any distortion is totally non-disturbing
- 50% = some disturbing side-effects, you don't have to
worry about glasses anymore, but the vision is far from perfect
- 0% = major difficulties at reading and recognizing faces,
driving a car at dark is hazardous (or other complications).
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100%, now that my eyes have "healed." I would say 75% for the first 3
months after surgery, gradually rising during the 3-month to 24 month
period to 100% now.
| Quote: | 10. Your pre-operative prescription, dilated pupil size, perfect correction
optical zone size and transition zone size (if you know them). And your age,
if you wish.
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-6.5 left, -6.0 right, 6.5 mm, but I don't know optical and transition
zone sizes. Age is 43.
| Quote: |
X. If you have something else to comment about your vision, please add it
here.
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I would just say that patience pays off. I was a little upset and the
starbursts/halos, and I certainly thought they would have "gone away"
quicker than they did. Now that they're practically unnoticeable, I
am a happy camper.
| Quote: | Thank you very much for your time and effort!
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No problem. Great idea!
> |
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