The cornea is the transparent front part of the eye that refracts light. It has five layers - epithelium, Bowman's layer, stroma, Descemet's membrane, and endothelium. The stroma comprises the majority of the cornea and contains collagen fibrils and proteoglycans responsible for its strength and transparency. The endothelium functions as a pump to remove fluid from the stroma and maintain corneal dehydration and transparency. Any disruption to this fluid regulation or the collagen structure can compromise the cornea's transparency.