1. An optically transparent element comprising: an optically transparent substrate; and an anti-reflective coating disposed on at least one surface of the optically transparent substrate, the anti-reflective coating comprising a polymer having an average particle size of between 1 nm and 100 nm, the polymer consisting essentially of tetraethoxy silane residues and methyltriethoxy silane residues; the polymer comprising at least 50 mole percent of the tetraalkoxy silane residues based on the total moles of polymer; the polymer comprising between 35 and 50 mole percent of the methyltriethoxy silane residues based on the total moles of polymer; and the anti-reflective coating having a refractive index of less than 1.28.