Postnatal human lens growth: finding the relationship between dimensions and weight

Abstract

Purpose : To examine the relationship between physical dimensions of human crystalline lenses and their weights during postnatal growth.

Methods : Crystalline lenses (n = 75, aged 3.8 – 88 years, median post-mortem time 25.5 hours) were isolated from donor eyes received by the Ramayamma International Eye Bank, Hyderabad, India. Equatorial diameter (D), axial thickness (T), cross-sectional area (CSA), surface area (SA) and volume (V) were calculated from coronal and sagittal profiles of the lenses imaged using a custom-built shadowphotogrammetric system (Mohamed et al, ARVO 2015). The wet weight (WW) and dry weight (DW) of the lenses were measured as described previously (Mohamed et al, IJO 2012). Allometric analysis of the relationship of dimensions to WW was performed by logarithmic transformation followed by least squares regression with 95% confidence intervals (CI).

Results : D, SA, V and WW increased throughout life, consistent with continuous growth of the lens. Remodeling of human lens decreased T (hence CSA) in the first two decades and then increased it for the rest of life. Figure 1 summarizes the results of allometric analysis. D and SA grew in isometric relationship with WW, whereas V had lower growth rate than WW (negative allometry). This is also reflected in the decreasing SA/V ratio of lens with age (y = 1.08 – 0.002*x; p<0.0001). From the second decade, T and CSA maintained an isometry with WW. DW also scales isometrically with WW (Figure 2) indicating that there is a constant accumulation of protein content with age during the postnatal lens growth.

Conclusions : This study demonstrates the relationship between various dimensions of lens with its contents during postnatal growth. It appears that all the dimensions grow isometrically with the increase in weight of the lens, due to its continuous growth. Continually decreasing ratios of surface area to volume ensure that geometrical similarity is maintained with size increase. This would have implications in the development of intraocular lens implants for the treatment of disorders such as cataracts and presbyopia.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Summary of wet weight vs dimensions allometry in lens (T and CSA – from age 20 years; Isometry = I lies within 95% CI of B; Negative allometry = I lies above 95% CI of B)

 

The allometry of dry weight to wet weight