Rationale and techniques of closed vitrectomy.

The three indications for vitrectomy are opacity causing severe visual deficit, vitreo-retinal traction causing or threatening retinal detachment, and displacement of the vitreous from its normal position. The types of pathology which cause opacity and/or traction and which are amenable to treatment by closed vitrectomy are lens changes or lens/iris remnants, opaque vitreous gel, ochre membranes, transgel traction bands, posterior hyaloid membranes, and epiretinal membranes. Closed vitrectomy has superseded the open sky method because the integrity of the cornea is preserved, the crystalline lens can be preserved, the intraocular pressure can be regulated, and the visualization and access to the posterior segment are good. More than 200 closed vitrectomies have been carried out at this hospital since 1974, using the Machemer VISC VII, the Douvas Rotoextractor, and the Peyman Vitrophage. The techniques which have been evolved as a result of experience with these instruments are demonstrated in a film.