Evolution and the Calcite Eye Lens

TL;DR

This paper examines the optical limitations of calcite as an eye lens due to birefringence and compares its performance to crystallin lenses, highlighting evolutionary adaptations for clear vision.

Contribution

It evaluates calcite-induced blurring in eye lenses and compares it with crystallin lenses, providing insights into evolutionary lens adaptations.

Findings

Calcite causes blurring when light is not aligned with its c-axis.

Crystallin lenses reduce blurring, offering clearer vision.

Calcite's birefringence limits its effectiveness as an eye lens.

Abstract

Calcite is a uniaxial, birefringent crystal, which in its optically transparent form, has been used for animal eye lenses, the trilobite being one such animal. Because of the calcite birefringence there is a difficulty in using calcite as a lens. When the propagation direction of incoming light is not exactly on the c-axis, the mages blur. In this paper, calcite blurring is evaluated, and the non-blurring by a crystallin eye lens is compared to a calcite one.