Birefringent properties of the cornea measured by a Mueller type polarimeter in healthy adults and children

Abstract

Mueller type polarimeter was used for in vivo measurements of the anisotropic parameters (retardation and azimuth angle) of corneas. To determine birefringence, corneal thickness was measured with a Scheimpflug camera (Corvist ST). The retardation distributions in the nasal-temporal cross-section in both children (N=7) and adults (N=38) groups occurred asymmetrical. The asymmetry in birefringence distributions was observed only in adults group. The geometrical analysis of the first order isochromes in both age groups showed the asymmetry of its shapes. The changes of symmetry in birefringent properties with age may have potential relationship with changing corneal biometry.

Fig. 1.

Exemplary results of experimental distribution of α (a, b) and γ (c, d). Left column (a, c) stands for the right eye and right column (b, d) for the left eye

Fig. 2.

Distribution of α: scheme of the radial representation of this distribution (a), scheme of tangential representation for three selected circles (b)

Fig. 3.

Distribution of γ described by a quadrilateral (sides lengths: B_NU, B_ND, B_TU, B_TD, vertex angles α_N, α_T, α_U, α_D) with marked lines of cross-sections (0, 90, +45, −45)

Fig. 4.

Box-plots of corneal thickness (CT) for adult (a) and children (b) groups in central area CCT, and nasal and temporal paracentral area measured in 3.5 mm and 4.0 mm (PCT_{N 3,5}, PCT_{N 4,0}, PCT­_{S 3,5}, PCT_{S 4,0}, respectively)

Fig. 5.

Box-plots of sides lengths (B_SG, B_NG, B_ND, B_SD) (a, b) and angles sizes between them (α_T, α_U, α_N, α_D) (c, d) for right and left eye in both age groups

Fig. 6.

Examples of retardation (R) (a, c, e) and birefringence (Δn) (b, d, f) distributions for adults (a-d) and children (e, f)