How Encircling Works

Similar to a circumferential buckle, encircling closes breaks by corking them functionally at the crest, interrupting the conduit of fluid through the hole. The constriction permanently reduces traction on the break and volume reduction concentrates the vitreous mass, both facilitating apposition of the retina and plugging of the tear. This may be particularly beneficial in small undetected full thickness holes, which remain relaxed, supported and corked and, therefore, may never become functional. As Gonin said, "La masse pulpaire du vitre, formant elle-meme bouchon au devant de l'ouverture, favorise cette obliteration" [7].

With and without intraocular injection of gas the inferior retina has been prone to break formation. In 1921, Gonin pointed to the traction-reducing effect of the weight of the vitreous mass on the inferior retina. He felt, however, that the inferior vitreous attachment was firmer and of larger surface, "En revanche, par suite du contact plus direct et plus durable qui existe entre la pulpe du vitre et la retine dans les parties declives, les adherences ont chances d'y etre plus intimes et plus etendues" [7].

Buckling of the vitreous base, as in encircling [14], might provide protection against increased vitreous traction, particularly inferior. Most vitreous proliferation starts inferiorly and is stimulated by trauma or vitreous manipulation. Gas bubbles, depending on buoyancy, may contribute to inferior traction directly. Encircling protects the vulnerable vitreous base, as seen by the paucity of retinal breaks after encircling as opposed to pneumatic retinopexy [15], and the barrier effect of prophylactic laser treatments, which include the inferior periphery [16].

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