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 that maintain the cornea's shape and strength. The endothelium functions as a pump to remove fluid from the stroma and maintain corneal dehydration and transparency. Any disruption to this fluid regulation can lead to corneal swelling and loss of transparency.