Creasing as a Candidate Mechanism of Foveal Pit Formation*

Foveal pits, a part of the macula structure within the eye, form during eye development in many species and are believed to contribute to high acuity vision. The foveal pits of anoles, a small lizard in the iguana family, have cusped shapes when viewed along the central axis. Anoles possess both temporal and central foveae, and their eyes contract along this axis during pit formation [1]. Under high intraocular pressure, a mound of cells forms and prepatterns the location of the fovea. Subsequent pressure reduction, appears to cause compression of the mound and trigger foveal pit formation [2], analogous to creasing in synthetic experiments. Creasing, observed in hyperelastic materials at around 35% compressive strain, is characterized by sharply localized surface deformations. This phenomenon is hypothesized to relate to foveal pit formation due to similarities in cross-sectional shape, ~33% retraction of the ocular globe prior to fovea development, and evidence of retinal compression during pit formation. Our research bridges synthetic creasing experiments with biological foveal development, offering insights into the role of mechanical forces in eye morphogenesis. In our experiment, a small puddle of elastomer mimics the foveal mound in a hemispherical elastomer bowl that is tensioned by a vacuum chamber. This tests the hypothesis that reduced intraocular pressure drives foveal pit formation. A "dimple," observed before creasing, suggests creasing may be an underlying mechanism of foveal pit formation. By studying crease morphology and dynamics in this synthetic experiment, we aim to better understand the mechanical forces in eye morphogenesis.

[1] Rasys, A. M., et al., Dev. Dyn. 250, 1584 (2021).

[2] Rasys, A. M., et al., BioEssays, 2300054 (2023).