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Rosario G Anera

Publications and source records attributed to Rosario G Anera.

7 recordsLinked to original sources
PubMed2005

Differences between real and predicted corneal shapes after aspherical corneal ablation.

We study the differences between real and expected corneal shapes, using an aspherical ablation algorithm with a known equation and avoiding the limitation imposed by most studies of refractive surgery in which the ablation equations are not known. We have calculated the theoretical corneal shape predicted by this algorithm, comparing this shape with the real corneal topography. The results indicate that the deviations that appear in the corneal shape are significant for visual performance and for the correction of eye aberrations. If we include in this analysis the effect of reflection losses and nonnormal incidence on the cornea, we can reduce corneal differences, but they will remain significant. These results confirm that it is essential to minimize corneal differences to achieve effective correction in refractive surgery.

Algorithms↗
PubMed2004

Influence of laser polarization on ocular refractive parameters after refractive surgery.

We provide an adjustment factor for ablation algorithms used in photorefractive laser surgery that takes into account how laser polarization in reflection losses affects the cornea. We evaluate the influence of this factor on corneal radius and asphericity after surgery, showing that it is significant for visual performance (effective visual acuity is reduced) and for the correction of eye aberrations. Our data indicate that this adjustment factor should be included in the ablation algorithms (depending on the polarization state of each laser device) that are proposed for customized corneal ablation, which need great accuracy for minimization of eye aberrations.

Eye↗
PubMed2003

Changes in corneal asphericity after laser refractive surgery, including reflection losses and nonnormal incidence upon the anterior cornea.

We tested the effects on laser ablation of reflection losses and nonnormal incidence on the anterior cornea. We measured presurgical and postsurgical corneal asphericity in 94 myopic eyes, comparing it with the corneal asphericity predicted by the Munnerlyn formula, modified or not, with an adjustment factor that takes into account the two effects mentioned above. The predictive power of the experimental results was stronger when we considered the adjustment factor. We propose to modify ablation algorithms by taking this adjustment factor into account, especially in customized corneal ablation, which needs high accuracy for correcting eye aberrations.

Corneal Topography↗
PubMed2003

Changes in corneal asphericity after laser in situ keratomileusis.

PURPOSE: To analyze the origin of the changes in corneal asphericity (p-factor) after laser in situ keratomileusis (LASIK) and the effect of postsurgery asphericity on contrast-sensitivity function (CSF) under photopic conditions. SETTING: Department of Optics, University of Granada, Granada, Spain. METHODS: The p-factor and CSF (best corrected before surgery and 1, 3, and 6 months after surgery) were measured in 24 eyes. RESULTS: An increase in the p-factor after LASIK was noted; there was an 87.2% change in the asphericity using the paraxial formula of Munnerlyn and coauthors. Other factors such as decentration, type of laser, optical role of the flap, wound healing, biomechanical effects, technical procedures, and reflection losses of the laser on the cornea could account for the greater than expected increase (12.8%) in the p-factor. The CSF measurements deteriorated after LASIK; the change was significant (P<.05) in patients with myopia worse than -4.0 diopters at frequencies of 9.2, 12, 15, and 20 cycles per degree. CONCLUSION: The increase in corneal asphericity after surgery, greater with a higher degree of myopia, and the deterioration in CSF with high myopia justify new ablation algorithms and further study of the variables that could modify the ablation unpredictably.

Adult↗
PubMedDate not supplied

Equation for corneal asphericity after corneal refractive surgery.

PURPOSE: To determine the exact theoretical asphericity after refractive surgery when the parabolic approximation of the Munnerlyn formula is utilized. METHOD: From a least-square analysis and considering the conicoid model for anterior cornea, we calculated the final asphericity (p'-factor) from the preoperative asphericity and the radii before and after surgery. RESULTS: The final p'-factor is given by p'=p(R'3/R3); R' is the final radius of curvature; R is the preoperative radius; and p is the preoperative p'-factor. CONCLUSIONS: This equation for postoperative asphericity may be useful in studying the influence on asphericity of different surgical variables. It allows comparisons of real asphericity with the asphericity that should theoretically result. It also explains the increased spherical aberration after refractive surgery and the deterioration of retinal image quality that some authors have found experimentally.

Cornea↗