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. 2021 Jan:202:108334.
doi: 10.1016/j.exer.2020.108334. Epub 2020 Oct 26.

Morphometric analysis of in vitro human crystalline lenses using digital shadow photogrammetry

Ashik Mohamed  1 , Heather A Durkee  2 , Siobhan Williams  2 , Fabrice Manns  3 , Arthur Ho  4 , Jean-Marie A Parel  3 , Robert C Augusteyn  5
Affiliations

Morphometric analysis of in vitro human crystalline lenses using digital shadow photogrammetry

Ashik Mohamed et al. Exp Eye Res. 2021 Jan.

Abstract

There is a great need for accurate biometric data on human lenses. To meet this, a compact tabletop optical comparator, the minishadowgraph, was built for measuring isolated eye lens shape and dimensions while the lens was fully immersed in supporting medium. The instrument was based around a specially designed cell and an illumination system which permitted image recording in both sagittal and equatorial (coronal) directions. Data were acquired with a digital camera and analyzed using a specially written MATLAB program as well as by manual measurements in image analysis software. The possible effect of lens orientation and gravity on the dimensions was examined by measuring dimensions with anterior or posterior surfaces up and by measuring lenses with calipers after removal from the minishadowgraph cell. Dimensions, curvatures and shape factors were obtained for 134 fully accommodated lenses ranging in age from birth to 88 years postnatal. Of these, 41 were from donors aged under 20 years, ages which are generally of limited availability. Thickness and diameter showed the same age-related trends described in previous studies but, for the lenses measured in air, age-dependent differences were observed in thickness (-5 to 0%) and diameter (+5 to 0%), consistent with gravitational sag. Anterior and posterior radii of curvature of the central 3 or 6 mm, depending on lens diameter, increase with age, with the anterior increase greater than the posterior. The anterior surface shape of the neonatal lens is that of a prolate ellipse and the posterior, an oblate ellipse. Both surfaces become hyperbolic after age 20. The data presented here on dimensions, shape and sagging will be of great value in assessing age-related changes in the optical and mechanical performance of the lens. In particular, the comprehensive data set from donors aged under 20 years provides a unique and valuable insight to the changes in size and shape during the early dynamic growth period of the lens.

Keywords: Conic shape factors; Dimensions; Gravitational sag; Human lens; Minishadowgraph; Radius of curvature.

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Conflict of interest statement

Declarations of interest: none

Figures

Figure 1:
Figure 1:
The digital mini-shadowgraph components. Left: Illumination system, Center: Optical schematic, Right: Tissue housing assembly and Positioning system. For sagittal views, LED 1 is on and LED 2 is off. For coronal views, LED 1 is off and LED 2 is on.
Figure 2.
Figure 2.
Coronal (top) and sagittal (bottom) of isolated human donor lenses. The anterior surface is to the right in all except the 5-year-old.
Figure 3.
Figure 3.
Lens Diameter (A) and Thickness (B), as a function of Age, obtained using CANVAS measurements. Data from lenses under age 20 are shown in red.
Figure 3.
Figure 3.
Lens Diameter (A) and Thickness (B), as a function of Age, obtained using CANVAS measurements. Data from lenses under age 20 are shown in red.
Figure 4.
Figure 4.
The relationship between Diameter and Thickness as a function of age: (A) Difference in the dimensions and (B) the aspect ratio (T/D). Data from lenses under age 20 are shown in red.
Figure 4.
Figure 4.
The relationship between Diameter and Thickness as a function of age: (A) Difference in the dimensions and (B) the aspect ratio (T/D). Data from lenses under age 20 are shown in red.
Figure 5.
Figure 5.
Anterior (A) and Posterior (B) thickness as a function of age. Data from lenses under age 20 are shown in red.
Figure 5.
Figure 5.
Anterior (A) and Posterior (B) thickness as a function of age. Data from lenses under age 20 are shown in red.
Figure 6.
Figure 6.
The ratio of anterior to posterior lens thickness as a function of age. Data from lenses under age 20 are shown in red.
Figure 7.
Figure 7.
Lens Anterior (A) and Posterior Radii of Curvature (B), as a function of Age. Radii obtained with the measured surface facing up are shown as solid symbols while those obtained with the surface facing down are shown as open symbols. Data from lenses under age 20 are shown in red. The conic radius is the radius of curvature obtained from the conic fit.
Figure 7.
Figure 7.
Lens Anterior (A) and Posterior Radii of Curvature (B), as a function of Age. Radii obtained with the measured surface facing up are shown as solid symbols while those obtained with the surface facing down are shown as open symbols. Data from lenses under age 20 are shown in red. The conic radius is the radius of curvature obtained from the conic fit.
Figure 8
Figure 8
Anterior (A) and Posterior (B) conic shape factor as a function of Age. Data from lenses under age 20 are shown in red. Shape factors obtained with the measured surface facing up are shown as solid symbols while those obtained with the surface facing down are shown as open symbols.
Figure 8
Figure 8
Anterior (A) and Posterior (B) conic shape factor as a function of Age. Data from lenses under age 20 are shown in red. Shape factors obtained with the measured surface facing up are shown as solid symbols while those obtained with the surface facing down are shown as open symbols.
Figure 9.
Figure 9.
The difference between measurements in air (calipers) and medium (minishadowgraph) of lens diameter (A) and thickness (B), as a function of age
Figure 9.
Figure 9.
The difference between measurements in air (calipers) and medium (minishadowgraph) of lens diameter (A) and thickness (B), as a function of age
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