Geometrical approximations for accurate evaluation of refraction in the human cornea

Espinosa, Julián; Rouarch, Jessica; Pérez, Jorge; Illueca, Carlos; Mas, David

doi:10.1016/j.ijleo.2006.03.014

Cited by 6 publications

(3 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In particular, the typical keratometric index is too high and results in an overestimation of the corneal optical power (Dubbelman et al. , 2006; Espinosa et al. , 2007).…”

Section: Introductionmentioning

confidence: 99%

“…Such a simple approach has several problems. In particular, the typical keratometric index is too high and results in an overestimation of the corneal optical power (Dubbelman et al, 2006;Espinosa et al, 2007). Moreover, although the second corneal surface only contributes 10% of the total refractive power of the eye, a precise knowledge of its morphology is needed for the correct diagnosis and monitoring of corneal diseases or surgical interventions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Correlation between the dioptric power, astigmatism and surface shape of the anterior and posterior corneal surfaces

Mas

Espinosa

Domenech

et al. 2009

Ophthalmic Physiologic Optic

Self Cite

View full text Add to dashboard Cite

A knowledge of the shape of the cornea is of major importance for the planning and monitoring of surgery, and for the correct diagnosis of corneal diseases. Many authors have studied the geometry of the second corneal surface in the central region and it has been stated that there is a high correlation between the central radii of curvature and asphericities of the two corneal surfaces. In this work we extend this study to a larger, central, 6-mm diameter of the cornea. Surface height data, obtained with an Oculus Pentacam from 42 eyes from 21 subjects, were analysed to yield surface power vectors. Corneal heights of both surfaces were also decomposed into low-order Zernike polynomials and the correlations between each of the power vectors and low-order Zernike coefficients for the two surfaces were studied. There was not only a strong correlation between spherical powers and Zernike defocus coefficients, but also between the astigmatic components. The correspondence between the astigmatisms in both surfaces found here can be of the utmost importance in planning optical surgery, since perfect spherical ablation of the first surface does not assure total correction of corneal astigmatism.

show abstract

“…In particular, the typical keratometric index is too high and results in an overestimation of the corneal optical power (Dubbelman et al. , 2006; Espinosa et al. , 2007).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Correlation between the dioptric power, astigmatism and surface shape of the anterior and posterior corneal surfaces

Mas

Espinosa

Domenech

et al. 2009

Ophthalmic Physiologic Optic

Self Cite

View full text Add to dashboard Cite

show abstract

“…Let us point out that, when using least squares to minimize the ' 2 -norm of the error, good approximation of a function does not mean good 235 approximation of its derivative. Thus, errors in heights have no direct correspondence with power errors and vice versa [12], as happens in Figure 4, where it can be seen that lower RMSD in height reconstruction does not assure a good optical modelling. Analysing a conic 240 surface with K ¼ À0.21, similar to a real cornea [13], we found that, although WLS fitting provides a slightly higher height-RMSD than OLS (4.10 Â 10 À4 versus 3.89 Â 10 À4 mm), the difference in the inner optical zone of pupil diameter 3 mm is almost one order of 245 magnitude lower (0.83 Â 10 À4 versus 4.88 Â 10 À4 mm).…”

Section: Resultsmentioning

confidence: 96%