We need to place a lid speculum to get the best exposure for cataract surgery, but if we crank it open too much it can exert a posterior pressure. This patient has a tight orbit and placement of the speculum to achieve the maximum palpebral fissure makes exposure of the anterior segment better. However, it also causes a posterior pressure which we notice when attempting the capsulorhexis.
This patient has a shallow anterior chamber and the added posterior pressure causes the viscoelastic to want to exit the phaco incision. The anterior lens capsule then becomes more dome-shaped instead of flat, and the capsulorhexis has a tendency to run-out.
After decreasing the posterior pressure by loosening the speculum, additional viscoelastic is instilled and the case can proceed normally.
Click below to see the effect of speculum loosening on posterior pressure: