Terriens Marginal Degeneration (TMD) is a special type of corneal marginal degeneration. It is rare and mainly manifested as chronic, bilateral corneal marginal atrophy and groove-like thinning of the corneal parenchyma accompanied by superficial neovascularization. Eventually, the cornea bulges forward, perforates, and iris prolapses, resulting in serious damage to the eyeball. It was first reported by Trumpy in 1881 as "transparent corneal degeneration". Terrien described it in more detail in 1900, calling it "marginal, asymmetric, dilated corneal atrophy". Since then, this disease has been reported in the literature, and clinical observations in recent years have provided a better understanding of this disease.