The study describes a series of experiments in which bovine corneal buttons, both with and without edematous epithelium, were hydrated to different thicknesses. The degree of light scattering and turbidity were determined for each thickness and related to visual acuity and glare sensitivity. For corneal buttons without epithelium, visual acuity dropped below 20/20 when thickness increased to 30% above base value, while glare sensitivity changed when thickness increased 10%. For edematous corneas with epithelium, visual acuity dropped below 20/20 when total corneal thickness increased 10%; glare sensitivity changed significantly when total corneal thickness increased 5%. Light scattering measurements and turbidity calculations in both kinds of corneas correlated with changes in visual acuity and glare sensitivity.
Lançon MR, Miller D. Corneal Hydration, Visual Acuity, and Glare Sensitivity. Arch Ophthalmol. 1973;90(3):227-230. doi:10.1001/archopht.1973.01000050229009