I know you should have stable vision for at least 1 year prior but what does "stable" mean exactly?

If your vision regresses between 0.25 to 0.5 diopters within a year are they still considered stable? Or is it better to wait until there is absolutely no change in your prescription for at least 1 year?

A change of 0.25 diopter in sphere is within normal fluctuations. You can blink a few times and make that much of a change.

A change of 0.50 diopter in sphere may indicate a progression of your refractive error.

Different techniques for measurement, different doctors, even times of the day, week, year when the evaluation is made can contribute to small changes in refractive error.

This is something best discussed with your doctor.

Glenn Hagele
http://www.USAEyes.org

I am not a doctor.

2005: R -5.00 -0.50 L -5.00 -0.50
2004: R -5.00 -0.50 L -5.00 -0.50
2003: R -5.00 L -4.50 -0.50
2002: R -4.50 L -4.50 -0.50

My optometrist thinks that I have adequate refractive stability. How will I know if they have definitely stablized?

half diopter in 3 years for both eyes isnt bad and represents a small change. If you are over 21 you may experience no major changes. Of course your eye may change another -.5 diopter in 5 years or something, lasik or no lasik.

In my case stability was only required for 3 months pre-op. Now six months post surgery I am informed that I have cataracts. I would appreciate any input on whether stability should have been measured for a longer period before putting me at risk of this.

Phil wrote: "In my case stability was only required for 3 months pre-op. Now six months post surgery I am informed that I have cataracts. I would appreciate any input on whether stability should have been measured for a longer period before putting me at risk of this."

I think you may be confusing two kinds of refractive stability, Phil. Type (1), the kind Kylie is referring to, is refractive stability over a period of at least a year while continuing to wear the same type of corrective lenses as usual (either glasses or contact lenses). Type (2) is refractive stability for a period of some weeks for contact lens wearers after they have discontinued wearing their lenses in preparation for surgery. Contact lenses cause temporary warping of the cornea (soft lenses less so than GP lenses), so doctors require patients to discontinue their use prior to surgery, and they perform sequential topographies to determine when the contact lens-induced warpage has fully resolved. Depending on the type of lens used, number of years of wear, and individual variability, this process can take from a few weeks to a few months. It sounds like type (2) refractive stability for contact lens wearers is likely the "3 months pre-op" stability you were told about, and, if so, it would be completely appropriate. Also, your doctor was already probably aware that you were okay with respect to type (1) stability from your records and history. So, it is likely you received proper care with respect to refractive stability. In addition, cataract formation is generally an age-related condition (50+) and is not caused by refractive surgery. A few people have conjectured that shock waves generated by the laser might stimulate a histological cascade that might trigger cataracts in susceptible patients, but this has never been demonstrated and, in fact, the rate of cataract formation in post-refractive surgery patients is the same as in the general population. So, long story short, your cataracts have nothing to do with your refractive surgery.

Bryce Carlson

>Message:
I usually answer questions on these pages, but now I've got one of my own that I hope Dr. Trattler or others knowledgeable about the VISX Star S2 laser can answer. I had bilateral LASIK in late May, 2000 on the VISX Star S2 laser. I had conventional 6.5 mm ablations; however, in the OS eye I had -1.25 D of astigmatism, so in that eye I had a toric elliptical ablation (6.5 mm x ~5.5 mm). One thing I have always wondered about in the ablation of the OS eye is that, even though I had no trouble fixating, the ablation was briefly stopped midway through while the surgeon reposition my head at an oblique angle several degrees from the vertical. Then, he resumed the ablation and completed the surgery. I wondered about this brief interruption in treatment at the time, but I somehow never got around to asking him about it. Later when I analyzed it, I assumed that what had happened is that the laser first ablated the entire 6.5 mm optical zone using the Rx of the flatter meridian, the!
n the surgeon stopped the procedure, repositioned my head to the proper angle, and proceeded with the toric correction of the steeper meridian. That makes sense, but it assumes the S2 laser could only be programmed to make toric corrections at 180 deg or 90 deg (with-the-rule, or against-the-rule astigmatism), and if the patient's axis of cylinder happened to be other than that (mine was 172 deg), the doctor had to reposition the patient's head, using the ink marks on the cornea and the reticule grid on the laser's viewing screen, to properly align the toric ablation at the correct meridian. It makes sense, IF you assume the S2 laser did not allow surgeon selection of the toric axis other than at 180 deg or 90 deg. But why should that be so? The VISX Star S4 is certainly axis selectable for toric ablations to any meridian, so it seems surprising that the S2 wasn't. So, can anyone tell me if my analysis is correct and the S2 laser had this axis-selection restriction in toric !
ablations, or if there was some other reason the doc briefly !
stopped the procedure and repositioned my head to a slightly different angle.

Bryce Carlson

The ablation does not take place in two stages as you suggest but takes place simultaneously. If you had a good surgeon, and it sounds like you did, he was observing that the dye marks he placed on your cornea preoperatively were rotating slightly as your eye possibly cyclotorqued, and he was repositioning your head to keep the pre placed alignment marks correctly oriented with the horizontal reference line he was observing in the reticule of the ocular. I do that frequently when I use the Visx. The alcon uses a horizontal reference line and you can rotate the actual ablation with the software and leave the patient's head alone.

Dr. Salz, Los Angeles

>Message:
I usually answer questions on these pages, but now I've got one of my own that I hope Dr. Trattler or others knowledgeable about the VISX Star S2 laser can answer. I had bilateral LASIK in late May, 2000 on the VISX Star S2 laser. I had conventional 6.5 mm ablations; however, in the OS eye I had -1.25 D of astigmatism, so in that eye I had a toric elliptical ablation (6.5 mm x ~5.5 mm). One thing I have always wondered about in the ablation of the OS eye is that, even though I had no trouble fixating, the ablation was briefly stopped midway through while the surgeon repositioned my head at an oblique angle several degrees from the vertical. Then, he resumed the ablation and completed the surgery. I wondered about this brief interruption in treatment at the time, but I somehow never got around to asking him about it. Later when I analyzed it, I assumed that what had happened is that the laser first ablated the entire 6.5 mm optical zone using the Rx of the flatter meridian, then the surgeon stopped the procedure, repositioned my head to the proper angle, and proceeded with the toric correction of the steeper meridian. That makes sense, but it assumes the S2 laser could only be programmed to make toric corrections at 180 deg or 90 deg (with-the-rule, or against-the-rule astigmatism), and if the patient's axis of cylinder happened to be other than that (mine was 172 deg), the doctor had to reposition the patient's head, using the ink marks on the cornea and the reticule grid on the laser's viewing screen, to properly align the toric ablation at the correct meridian. It makes sense, IF you assume the S2 laser did not allow surgeon selection of the toric axis other than at 180 deg or 90 deg. But why should that be so? The VISX Star S4 is certainly axis selectable for toric ablations to any meridian, so it seems surprising that the S2 wasn't. So, can anyone tell me if my analysis is correct and the S2 laser had this axis-selection restriction in toric ablations, or if there was some other reason the doc briefly stopped the procedure and repositioned my head to a slightly different angle.

Bryce Carlson

The ablation does not take place in two stages as you suggest but takes place simultaneously. If you had a good surgeon, and it sounds like you did, he was observing that the dye marks he placed on your cornea preoperatively were rotating slightly as your eye possibly cyclotorqued, and he was repositioning your head to keep the pre-placed alignment marks correctly oriented with the horizontal reference line he was observing in the reticule of the ocular. I do that frequently when I use the Visx. The alcon uses a horizontal reference line and you can rotate the actual ablation with the software and leave the patient's head alone.

Dr. Salz, Los Angeles

Thanks for your reply, Dr. Salz. This idea (cyclotorsion) occurred to me while I was reading Dr. Trattler's reply to my above post over on the Main page, and I posted a follow-up question to him about it. Based on what you say, I think that probably was what happened. And, yes, I had a good surgeon (Andy Caster).

Bryce

Dr. Salz stated, "The ablation does not take place in two stages as you suggest but takes place simultaneously."

I wonder if you would clarify that statement for me, Dr. Salz. It seems, based on what I understand about conventional LASIK ablations, that it is a semantic distinction without a real difference. What I mean by that is that the only difference between the ablation on the flatter meridian, and the one on the steeper meridian is the one on the steeper meridian is deeper by the amount of the cylinder. So, say, you had a patient with an Rx of -4 D, -1 D x 170 deg. In that case, the 170 deg meridian would get an ablation -4 D deep, and the 80 deg meridian would get one -5 D deep (-4 D plus -1 D). Consequently, regardless of whether the laser "thinks" it is doing the spherical (-4 D) part first, and then the (-1 D) cylinder, or both parts simultaneously, the reality is if the ablation is interrupted at or before it reaches -4 D in depth on both meridians, the two scenarios (sequential or simultaneous) are clinically identical, because the steeper meridian's ablation merely builds on the pulses that constitute the flatter meridian's ablation. If this analysis is wrong, perhaps you can set me straight as to just what the clinical difference between the two scenarios (sequential and simultaneous) actually is.

Bryce

Dr. Salz stated, "The ablation does not take place in two stages as you suggest but takes place simultaneously."

I wonder if you would clarify that statement for me, Dr. Salz. It seems, based on what I understand about conventional LASIK ablations, that it is a semantic distinction without a real difference. What I mean by that is that the only difference between the ablation on the flatter meridian, and the one on the steeper meridian is the one on the steeper meridian is deeper by the amount of the cylinder. So, say, you had a patient with an Rx of -4 D, -1 D x 170 deg. In that case, the 170 deg meridian would get an ablation -4 D deep, and the 80 deg meridian would get one -5 D deep (-4 D plus -1 D). Consequently, regardless of whether the laser "thinks" it is doing the spherical (-4 D) part first, and then the (-1 D) cylinder, or both parts simultaneously, the reality is the two scenarios (sequential or simultaneous) are clinically identical, because the steeper meridian's ablation merely builds on the pulses that constitute the flatter meridian's ablation. If this analysis is wrong, perhaps you can set me straight as to just what the clinical difference between the two scenarios (sequential and simultaneous) actually is.

Bryce

>Dr. Salz stated, "The ablation does not
>take place in two stages as
>you suggest but takes place simultaneously."
>

>I wonder if you would clarify that
>statement for me, Dr. Salz.
>It seems, based on what I
>understand about conventional LASIK ablations, that
>it is a semantic distinction without
>a real difference. What I
>mean by that is that the
>only difference between the ablation on
>the flatter meridian, and the one
>on the steeper meridian is the
>one on the steeper meridian is
>deeper by the amount of the
>cylinder. So, say, you had
>a patient with an Rx of
>-4 D, -1 D x 170
>deg. In that case, the
>170 deg meridian would get an
>ablation -4 D deep, and the
>80 deg meridian would get one
>-5 D deep (-4 D plus
>-1 D). Consequently, regardless of
>whether the laser "thinks" it is
>doing the spherical (-4 D) part
>first, and then the (-1 D)
>cylinder, or both parts simultaneously, the
>reality is if the ablation is
>interrupted at or before it reaches
>-4 D in depth on both
>meridians, the two scenarios (sequential or
>simultaneous) are clinically identical, because the
>steeper meridian's ablation merely builds on
>the pulses that constitute the flatter
>meridian's ablation. If this analysis
>is wrong, perhaps you can set
>me straight as to just what
>the clinical difference between the two
>scenarios (sequential and simultaneous) actually is.
>

>Bryce

You have it right for the Alcon and I think for the Visx. if you are having an ablation with the alcon unit in the above description and the power failed and the laser stoped exactly half way through the ablation, half your spehere and half your cylinder would be corrected and you would be left with -2 sphere and -0.5 cyl

Oh, okay, I get it now. Right from the gitgo and throughout the ablation the laser is preferentially laying down more pulses along the steeper meridian than it is along the flatter meridian. In the patient example I gave for instance (-4 D, -1 D x 170) the laser would hit the 80 deg meridian with 5 pulses for every 4 it placed along the 170 deg meridian. Thanks for your reply, Dr. Salz.

Bryce