what's the opening corner? Internal and external canthoplasty is commonly known as open canthus. It is to correct and enlarge the inner and outer corners of the eyes by surgery, so as to remove the epicanthus and extend the horizontal length of the eye fissure to achieve the effect of magnifying the eyes. The inner and outer canthoplasty was first used to correct microphthalmia. Congenital microphthalmia often requires multiple operations because of narrow eyelid fissure and severe epicanthus, as well as widening inner canthus space and ptosis. At present, with the development of cosmetic medicine and the increasing requirements of beauty lovers, inner and outer canthoplasty is also used for more normal people who pursue big eyes.