Complications Through the Use of Viscoelastics

Viscoelastic material retained behind the lOL may cause a capsular bag distension in the early postoperative period. These eyes accumulate a transparent substance in the closed chamber inside the capsular bag from the lOL blocking the capsular opening. The capsular bag distension was first discribed by Davison in 1990. Miyake et al. proposed a new classification of capsular block syndrome and supposed viscoelastic material to cause early-postoperative capsular block syndrome (Miyake et al., 1999). Capsular bag distension after optic capture of a sulcus-fixated lOL was described by Basti et al. (1999). 

Complications from the use of viscoelastic substances occur either as a result of improper injection (e.g., overfilling) or incomplete removal. 

The molecular size of viscoelastics protects from diffusion. Viscoelastics pass out of the eye through the trabecular meshwork as a large, usually unchanged molecule (Berson, Patterson 8c Epstein, 1983). As contractile elements are present both within the trabecular meshwork and ciliary body, this process is probably dynamic (Balazs, 1983). Several rabbit studies prove that sodium hyaluronate is carried away by both the episcleral veins as well as the mucoscleral pathway, followed by hyaluronidase break down within the tissues (Iwata, Miyauchi 8c Ta-kehana, 1984 Iwata 8c Miyauchi, 1985 Miyauchi 8c Iwata, 1984,1986). 

In cadaver eyes, sodium hyaluronate lessened aqueous outflow. Irrigation did not restore outflow facilities. Subsequently injected hyaluronidase was, however, effective in animal and human studies (Baranyl956 Calder Smith, 1986 Lang, Mark 8c Miller, 1984). 

Miller (1989) led comparative studies on intraocular pressure after injection and retention of Healon and Viscoat into monkey eyes (Fig. 57). Seven monkeys were injected (through a paracentesis) with Healon into one eye and Vis-coat into the other. Two monkeys served as controls, receiving physiological saline solution. Intraocular pressure was measured pneumatonometrically at 30 minute intervals. Maximal values were noted between 4 and 6 hours later, with intraocular pressure normalizing after 24 hours. 

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