Enhancement Procedure for Small Abalation Zone

Discussion in 'Optometry Archives' started by MSL, Aug 24, 2003.

  1. MSL

    MSL Guest

    I had bilateral Lasik done for myopia (-6D both eyes) 7 weeks ago. I am
    slightly under-corrected (-0.5D in R eye, -0.75D in L eye); this is not a
    problem to me. My vision is good in bright light.

    My problem is poor low-light vision: the usual haloes etc, and blurring in
    even relatively low light, not just at.night. At a follow-up visit, my
    ablation/optical zone was found to be significantly smaller than my pupil
    size in low light (I forget the actual figures). The optical zone is well
    centred. My residual corneal bed thicknesses are 285 micron right eye, and
    302 micron left eye. I am 43 years old.

    Does anyone have experience of enhancement prodecures to enlarge the optical
    zone? Is it possible with the above information? Would it help my low-light

    I would greatly appreciate any info, from eye-care professionals, and
    especially from patients.



    (Please remove 123 from e-mail address when replying).
    MSL, Aug 24, 2003
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  2. Hi Mike,

    I'm sorry to hear about your problems.

    At seven weeks postop you can expect some improvement with healing and
    adaptation, however it appears that your problems are significant and
    may not be resolved with healing. I suggest that you not do anything
    surgically to correct this problem until at least three months postop.
    Delaying treatment should not be problematic. Contacts, glasses, and
    eye drops should be fine, but you want things to settle down before
    any additional surgery.

    For more information how pupil size affects refractive surgery
    outcomes, visit http://www.complicatedeyes.org/pupil_size.htm

    You should look into getting fitted with rigid gas-permeable (RGP)
    contact lenses. Often this type of contact will reduce or eliminate
    the problem, but this is obviously only a management response, not a

    You could ask your doctor to prescribe Alphagan C drops. These drops
    will cause your iris to constrict, making the pupil smaller. This may
    also help managed the problem until a permanent resolution is found.

    Most doctors are looking toward Complex Wavefront Retreatment (CWR)
    for situations like yours. Although it is easiest to think of
    "expanding the treatment zone" as the answer, CWR would look at your
    cornea from a perspective of what is happening to the light passing
    through your eye, rather than what has been done to the surface of
    your cornea. This perspective will provide a detailed analysis of the
    Higher Order Aberrations (HOA) that are causing or contributing to
    your low light vision problems. Laser treatment that is guided by
    this wavefront analysis will attempt to correct the HOA that are
    caused by the irregularities in your cornea, including the ablation
    size issue.

    There are not many surgeons in the US or abroad that are performing
    CWR, and fewer who have much experience in this area. If you would
    like a referral to a doctor for contacts, drops, or evaluation for
    CWR, contact me directly.

    Your undercorrection is both advantageous and problematic. At age 43,
    you would start to suffer the effects of presbyopia (needing reading
    glasses). Being slightly undercorrected in your non-dominant eye may
    help defer the need for reading glasses. You should consider
    monovision correction if you have an enhancement or wear contacts.
    For more on monovision, visit

    Being undercorrected provides a margin of error for any retreatment
    without overcorrecting you into hyperopia (farsightedness). You
    really don't want to be hyperopic and presbyopic. This combination
    provides poor vision at almost all distances.

    Although monovision may defer or reduce your need for reading glasses,
    your current undercorrection may be contributing to your low light
    vision problems. If the halo and other night vision problems
    dissipate with glasses (not contacts) that fully correct your vision,
    then the undercorrection is contributing to the problem.

    Glenn Hagele
    Executive Director
    Council for Refractive Surgery Quality Assurance
    glenn dot hagele at usaeyes dot org

    I am not a doctor.
    Glenn Hagele - Council for Refractive Surgery Qual, Aug 24, 2003
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  3. Results differ, but here's one story.

    Why aren people getting treatment zones too small in the first place?
    Every new treatment reduces the cornea thickness and increases the
    lasik advocate with flap melt, Aug 25, 2003
  4. MSL

    Dr. Leukoma Guest

    Your situation might be improved by a system called TOSCA, for Topography
    Supported Customized Ablation. Using a small beam laser, such as a Mel 70
    or Mel 80, the system generates a customized ablation profile from
    topography and ablates the difference between the smaller optical zone and
    the larger optical zone. One can see an excellent presentation on this
    subject at the following website: www.mitchelleyecentre.com .

    Otherwise, consider contact lenses.

    Dr. Leukoma, Aug 25, 2003
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