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Related Experiment Videos

Corneal asphericity and visual function after radial keratotomy

J F Fleming1

  • 1Eye Institute, St. John Medical Center, Tulsa, Oklahoma.

Cornea
|May 1, 1993
PubMed
Summary
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Radial keratotomy surgery impacts corneal asphericity. Smaller surgical zones lead to increased negative asphericity, enhancing uncorrected visual acuity by improving depth of field.

Area of Science:

  • Ophthalmology
  • Corneal Surgery
  • Refractive Error Correction

Background:

  • Radial keratotomy (RK) is a refractive surgical procedure to correct myopia.
  • Corneal asphericity, a measure of corneal shape deviation from a perfect sphere, influences visual quality.
  • Understanding the relationship between RK parameters and postoperative corneal shape is crucial for visual outcomes.

Purpose of the Study:

  • To investigate the correlation between radial keratotomy clear zone size and postoperative corneal asphericity.
  • To determine the association between postoperative corneal asphericity and uncorrected visual acuity (UCVA) after RK.
  • To explore the potential mechanism by which corneal asphericity affects visual performance in RK patients.

Main Methods:

  • Corneal asphericity was measured in 81 eyes before and after RK using keratoscope rings.

Related Experiment Videos

  • Asphericity was calculated between specific keratoscope rings (2 and 9) corresponding to corneal diameters of 2.3 mm and 7.6 mm.
  • Statistical analyses, including correlation and Mann-Whitney U tests, were employed to assess relationships between surgical parameters, asphericity, and UCVA.

    • Main Results:

    • A significant correlation was found between smaller RK clear zones and greater negative postoperative asphericity (R = 0.74, p < 0.0001).
    • Eyes with smaller clear zones (< 4.0 mm) exhibited high mean negative asphericity (-6.44).
    • Within the smaller clear zone group, higher levels of negative asphericity were associated with better UCVA (Mann-Whitney U test, p < 0.0001).

    Conclusions:

    • Smaller clear zones in RK surgery lead to increased negative corneal asphericity.
    • Increased negative asphericity may beneficially increase the depth of field.
    • This effect could explain why some RK patients with residual refractive error achieve better-than-expected UCVA.