Hydroexpression and viscoexpression of the nucleus through a continuous circular capsulorhexis.

When a continuous circular capsulorhexis (CCC) is performed, conventional nucleus expression may be impossible because of the strong capsular rim. Hydroexpression of the nucleus seems to overcome the problem if the capsulorhexis opening is large enough. Because a viscoelastic material may be an even more gentle tool than balanced salt solution (BSS), hydroexpression and viscoexpression were evaluated in 16 pairs of human cadaver eyes. The diameter of the capsulorhexis opening ranged from 4 mm to 6 mm; it was the same in each pair of eyes. Hydroexpression was performed in one eye using BSS and viscoexpression was performed in the fellow eye using sodium hyaluronate (Healon Yellow). The fluid pressure in the capsular bag was measured during both procedures. The pressure was higher during hydroexpression than during viscoexpression. The pressure difference between fellow eyes ranged from 0 to 32 mm Hg and was most marked when the CCC opening was small. This correlation was significant (P < .05). Viscoexpression may enhance the safety in cases with a small CCC opening or in those that are otherwise difficult.